Move all C code into repo.

6 files changed, 6306 insertions, 0 deletions

diff --git a/cursor.go b/cursor.go
index 8399b88..2bf8318 100644
--- a/cursor.go
+++ b/cursor.go
@@ -9,6 +9,9 @@ package bolt
 // TODO: #define C_SPLITTING	0x20		/**< Cursor is in page_split */
 // TODO: #define C_UNTRACK	0x40		/**< Un-track cursor when closing */
 
+// TODO: #define MDB_NOSPILL	0x8000 /** Do not spill pages to disk if txn is getting full, may fail instead */
+
+
 type Cursor interface {
 	First() error
 	FirstDup() error
@@ -42,3 +45,3557 @@ type cursor struct {
 	page        []*page
 	ki          []int /**< stack of page indices */
 }
+
+// Set or clear P_KEEP in dirty, non-overflow, non-sub pages watched by txn.
+// @param[in] mc A cursor handle for the current operation.
+// @param[in] pflags Flags of the pages to update:
+// P_DIRTY to set P_KEEP, P_DIRTY|P_KEEP to clear it.
+// @param[in] all No shortcuts. Needed except after a full #mdb_page_flush().
+// @return 0 on success, non-zero on failure.
+func (c *cursor) xkeep(unsigned pflags, int all) int {
+	/*
+	enum { Mask = P_SUBP|P_DIRTY|P_KEEP };
+	MDB_txn *txn = mc->mc_txn;
+	MDB_cursor *m3;
+	MDB_xcursor *mx;
+	MDB_page *dp, *mp;
+	MDB_node *leaf;
+	unsigned i, j;
+	int rc = MDB_SUCCESS, level;
+
+	// Mark pages seen by cursors
+	if (mc->mc_flags & C_UNTRACK)
+		mc = NULL;				// will find mc in mt_cursors
+	for (i = txn->mt_numdbs;; mc = txn->mt_cursors[--i]) {
+		for (; mc; mc=mc->mc_next) {
+			if (!(mc->mc_flags & C_INITIALIZED))
+				continue;
+			for (m3 = mc;; m3 = &mx->mx_cursor) {
+				mp = NULL;
+				for (j=0; j<m3->mc_snum; j++) {
+					mp = m3->mc_pg[j];
+					if ((mp->mp_flags & Mask) == pflags)
+						mp->mp_flags ^= P_KEEP;
+				}
+				mx = m3->mc_xcursor;
+				// Proceed to mx if it is at a sub-database
+				if (! (mx && (mx->mx_cursor.mc_flags & C_INITIALIZED)))
+					break;
+				if (! (mp && (mp->mp_flags & P_LEAF)))
+					break;
+				leaf = NODEPTR(mp, m3->mc_ki[j-1]);
+				if (!(leaf->mn_flags & F_SUBDATA))
+					break;
+			}
+		}
+		if (i == 0)
+			break;
+	}
+
+	if (all) {
+		// Mark dirty root pages
+		for (i=0; i<txn->mt_numdbs; i++) {
+			if (txn->mt_dbflags[i] & DB_DIRTY) {
+				pgno_t pgno = txn->mt_dbs[i].md_root;
+				if (pgno == P_INVALID)
+					continue;
+				if ((rc = mdb_page_get(txn, pgno, &dp, &level)) != MDB_SUCCESS)
+					break;
+				if ((dp->mp_flags & Mask) == pflags && level <= 1)
+					dp->mp_flags ^= P_KEEP;
+			}
+		}
+	}
+
+	return rc;
+	*/
+	return 0
+}
+
+//	Spill pages from the dirty list back to disk.
+// This is intended to prevent running into #MDB_TXN_FULL situations,
+// but note that they may still occur in a few cases:
+//	1) our estimate of the txn size could be too small. Currently this
+//	 seems unlikely, except with a large number of #MDB_MULTIPLE items.
+//	2) child txns may run out of space if their parents dirtied a
+//	 lot of pages and never spilled them. TODO: we probably should do
+//	 a preemptive spill during #mdb_txn_begin() of a child txn, if
+//	 the parent's dirty_room is below a given threshold.
+//
+// Otherwise, if not using nested txns, it is expected that apps will
+// not run into #MDB_TXN_FULL any more. The pages are flushed to disk
+// the same way as for a txn commit, e.g. their P_DIRTY flag is cleared.
+// If the txn never references them again, they can be left alone.
+// If the txn only reads them, they can be used without any fuss.
+// If the txn writes them again, they can be dirtied immediately without
+// going thru all of the work of #mdb_page_touch(). Such references are
+// handled by #mdb_page_unspill().
+//
+// Also note, we never spill DB root pages, nor pages of active cursors,
+// because we'll need these back again soon anyway. And in nested txns,
+// we can't spill a page in a child txn if it was already spilled in a
+// parent txn. That would alter the parent txns' data even though
+// the child hasn't committed yet, and we'd have no way to undo it if
+// the child aborted.
+//
+// @param[in] m0 cursor A cursor handle identifying the transaction and
+//	database for which we are checking space.
+// @param[in] key For a put operation, the key being stored.
+// @param[in] data For a put operation, the data being stored.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) spill(MDB_val *key, MDB_val *data) int {
+	/*
+	MDB_txn *txn = m0->mc_txn;
+	MDB_page *dp;
+	MDB_ID2L dl = txn->mt_u.dirty_list;
+	unsigned int i, j, need;
+	int rc;
+
+	if (m0->mc_flags & C_SUB)
+		return MDB_SUCCESS;
+
+	// Estimate how much space this op will take
+	i = m0->mc_db->md_depth;
+	// Named DBs also dirty the main DB
+	if (m0->mc_dbi > MAIN_DBI)
+		i += txn->mt_dbs[MAIN_DBI].md_depth;
+	// For puts, roughly factor in the key+data size
+	if (key)
+		i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize;
+	i += i;	// double it for good measure
+	need = i;
+
+	if (txn->mt_dirty_room > i)
+		return MDB_SUCCESS;
+
+	if (!txn->mt_spill_pgs) {
+		txn->mt_spill_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX);
+		if (!txn->mt_spill_pgs)
+			return ENOMEM;
+	} else {
+		// purge deleted slots
+		MDB_IDL sl = txn->mt_spill_pgs;
+		unsigned int num = sl[0];
+		j=0;
+		for (i=1; i<=num; i++) {
+			if (!(sl[i] & 1))
+				sl[++j] = sl[i];
+		}
+		sl[0] = j;
+	}
+
+	// Preserve pages which may soon be dirtied again
+	if ((rc = mdb_pages_xkeep(m0, P_DIRTY, 1)) != MDB_SUCCESS)
+		goto done;
+
+	// Less aggressive spill - we originally spilled the entire dirty list,
+	// with a few exceptions for cursor pages and DB root pages. But this
+	// turns out to be a lot of wasted effort because in a large txn many
+	// of those pages will need to be used again. So now we spill only 1/8th
+	// of the dirty pages. Testing revealed this to be a good tradeoff,
+	// better than 1/2, 1/4, or 1/10.
+	if (need < MDB_IDL_UM_MAX / 8)
+		need = MDB_IDL_UM_MAX / 8;
+
+	// Save the page IDs of all the pages we're flushing
+	// flush from the tail forward, this saves a lot of shifting later on.
+	for (i=dl[0].mid; i && need; i--) {
+		MDB_ID pn = dl[i].mid << 1;
+		dp = dl[i].mptr;
+		if (dp->mp_flags & P_KEEP)
+			continue;
+		// Can't spill twice, make sure it's not already in a parent's
+		// spill list.
+		if (txn->mt_parent) {
+			MDB_txn *tx2;
+			for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) {
+				if (tx2->mt_spill_pgs) {
+					j = mdb_midl_search(tx2->mt_spill_pgs, pn);
+					if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == pn) {
+						dp->mp_flags |= P_KEEP;
+						break;
+					}
+				}
+			}
+			if (tx2)
+				continue;
+		}
+		if ((rc = mdb_midl_append(&txn->mt_spill_pgs, pn)))
+			goto done;
+		need--;
+	}
+	mdb_midl_sort(txn->mt_spill_pgs);
+
+	// Flush the spilled part of dirty list
+	if ((rc = mdb_page_flush(txn, i)) != MDB_SUCCESS)
+		goto done;
+
+	// Reset any dirty pages we kept that page_flush didn't see
+	rc = mdb_pages_xkeep(m0, P_DIRTY|P_KEEP, i);
+
+done:
+	txn->mt_flags |= rc ? MDB_TXN_ERROR : MDB_TXN_SPILLS;
+	return rc;
+	/*
+	return 0
+}
+
+// Allocate page numbers and memory for writing.  Maintain me_pglast,
+// me_pghead and mt_next_pgno.
+//
+// If there are free pages available from older transactions, they
+// are re-used first. Otherwise allocate a new page at mt_next_pgno.
+// Do not modify the freedB, just merge freeDB records into me_pghead[]
+// and move me_pglast to say which records were consumed.  Only this
+// function can create me_pghead and move me_pglast/mt_next_pgno.
+// @param[in] mc cursor A cursor handle identifying the transaction and
+//	database for which we are allocating.
+// @param[in] num the number of pages to allocate.
+// @param[out] mp Address of the allocated page(s). Requests for multiple pages
+//  will always be satisfied by a single contiguous chunk of memory.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) allocPage(int num, MDB_page **mp) {
+	int rc, retry = INT_MAX;
+	MDB_txn *txn = mc->mc_txn;
+	MDB_env *env = txn->mt_env;
+	pgno_t pgno, *mop = env->me_pghead;
+	unsigned i, j, k, mop_len = mop ? mop[0] : 0, n2 = num-1;
+	MDB_page *np;
+	txnid_t oldest = 0, last;
+	MDB_cursor_op op;
+	MDB_cursor m2;
+
+	*mp = NULL;
+
+	// If our dirty list is already full, we can't do anything
+	if (txn->mt_dirty_room == 0) {
+		rc = MDB_TXN_FULL;
+		goto fail;
+	}
+
+	for (op = MDB_FIRST;; op = MDB_NEXT) {
+		MDB_val key, data;
+		MDB_node *leaf;
+		pgno_t *idl, old_id, new_id;
+
+		// Seek a big enough contiguous page range. Prefer
+		// pages at the tail, just truncating the list.
+		if (mop_len > n2) {
+			i = mop_len;
+			do {
+				pgno = mop[i];
+				if (mop[i-n2] == pgno+n2)
+					goto search_done;
+			} while (--i > n2);
+			if (Max_retries < INT_MAX && --retry < 0)
+				break;
+		}
+
+		if (op == MDB_FIRST) {	// 1st iteration
+			// Prepare to fetch more and coalesce
+			oldest = mdb_find_oldest(txn);
+			last = env->me_pglast;
+			mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
+			if (last) {
+				op = MDB_SET_RANGE;
+				key.mv_data = &last; // will look up last+1
+				key.mv_size = sizeof(last);
+			}
+		}
+
+		last++;
+		// Do not fetch more if the record will be too recent
+		if (oldest <= last)
+			break;
+		rc = mdb_cursor_get(&m2, &key, NULL, op);
+		if (rc) {
+			if (rc == MDB_NOTFOUND)
+				break;
+			goto fail;
+		}
+		last = *(txnid_t*)key.mv_data;
+		if (oldest <= last)
+			break;
+		np = m2.mc_pg[m2.mc_top];
+		leaf = NODEPTR(np, m2.mc_ki[m2.mc_top]);
+		if ((rc = mdb_node_read(txn, leaf, &data)) != MDB_SUCCESS)
+			return rc;
+
+		idl = (MDB_ID *) data.mv_data;
+		i = idl[0];
+		if (!mop) {
+			if (!(env->me_pghead = mop = mdb_midl_alloc(i))) {
+				rc = ENOMEM;
+				goto fail;
+			}
+		} else {
+			if ((rc = mdb_midl_need(&env->me_pghead, i)) != 0)
+				goto fail;
+			mop = env->me_pghead;
+		}
+		env->me_pglast = last;
+#if (MDB_DEBUG) > 1
+		DPRINTF(("IDL read txn %"Z"u root %"Z"u num %u",
+			last, txn->mt_dbs[FREE_DBI].md_root, i));
+		for (k = i; k; k--)
+			DPRINTF(("IDL %"Z"u", idl[k]));
+#endif
+		// Merge in descending sorted order
+		j = mop_len;
+		k = mop_len += i;
+		mop[0] = (pgno_t)-1;
+		old_id = mop[j];
+		while (i) {
+			new_id = idl[i--];
+			for (; old_id < new_id; old_id = mop[--j])
+				mop[k--] = old_id;
+			mop[k--] = new_id;
+		}
+		mop[0] = mop_len;
+	}
+
+	// Use new pages from the map when nothing suitable in the freeDB
+	i = 0;
+	pgno = txn->mt_next_pgno;
+	if (pgno + num >= env->me_maxpg) {
+			DPUTS("DB size maxed out");
+			rc = MDB_MAP_FULL;
+			goto fail;
+	}
+
+search_done:
+	if (env->me_flags & MDB_WRITEMAP) {
+		np = (MDB_page *)(env->me_map + env->me_psize * pgno);
+	} else {
+		if (!(np = mdb_page_malloc(txn, num))) {
+			rc = ENOMEM;
+			goto fail;
+		}
+	}
+	if (i) {
+		mop[0] = mop_len -= num;
+		// Move any stragglers down 
+		for (j = i-num; j < mop_len; )
+			mop[++j] = mop[++i];
+	} else {
+		txn->mt_next_pgno = pgno + num;
+	}
+	np->mp_pgno = pgno;
+	mdb_page_dirty(txn, np);
+	*mp = np;
+
+	return MDB_SUCCESS;
+
+fail:
+	txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+	*/
+	return 0
+}
+
+// Copy the used portions of a non-overflow page.
+// @param[in] dst page to copy into
+// @param[in] src page to copy from
+// @param[in] psize size of a page
+func (p *page) copyTo(dst *page, size int) {
+	/*
+	enum { Align = sizeof(pgno_t) };
+	indx_t upper = src->mp_upper, lower = src->mp_lower, unused = upper-lower;
+
+	// If page isn't full, just copy the used portion. Adjust
+	// alignment so memcpy may copy words instead of bytes.
+	if ((unused &= -Align) && !IS_LEAF2(src)) {
+		upper &= -Align;
+		memcpy(dst, src, (lower + (Align-1)) & -Align);
+		memcpy((pgno_t *)((char *)dst+upper), (pgno_t *)((char *)src+upper),
+			psize - upper);
+	} else {
+		memcpy(dst, src, psize - unused);
+	}
+	*/
+}
+
+// Touch a page: make it dirty and re-insert into tree with updated pgno.
+// @param[in] mc cursor pointing to the page to be touched
+// @return 0 on success, non-zero on failure.
+func (c *cursor) page_touch() int {
+	/*
+	MDB_page *mp = mc->mc_pg[mc->mc_top], *np;
+	MDB_txn *txn = mc->mc_txn;
+	MDB_cursor *m2, *m3;
+	pgno_t	pgno;
+	int rc;
+
+	if (!F_ISSET(mp->mp_flags, P_DIRTY)) {
+		if (txn->mt_flags & MDB_TXN_SPILLS) {
+			np = NULL;
+			rc = mdb_page_unspill(txn, mp, &np);
+			if (rc)
+				goto fail;
+			if (np)
+				goto done;
+		}
+		if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) ||
+			(rc = mdb_page_alloc(mc, 1, &np)))
+			goto fail;
+		pgno = np->mp_pgno;
+		DPRINTF(("touched db %d page %"Z"u -> %"Z"u", DDBI(mc),
+			mp->mp_pgno, pgno));
+		mdb_cassert(mc, mp->mp_pgno != pgno);
+		mdb_midl_xappend(txn->mt_free_pgs, mp->mp_pgno);
+		// Update the parent page, if any, to point to the new page
+		if (mc->mc_top) {
+			MDB_page *parent = mc->mc_pg[mc->mc_top-1];
+			MDB_node *node = NODEPTR(parent, mc->mc_ki[mc->mc_top-1]);
+			SETPGNO(node, pgno);
+		} else {
+			mc->mc_db->md_root = pgno;
+		}
+	} else if (txn->mt_parent && !IS_SUBP(mp)) {
+		MDB_ID2 mid, *dl = txn->mt_u.dirty_list;
+		pgno = mp->mp_pgno;
+		// If txn has a parent, make sure the page is in our
+		// dirty list.
+		if (dl[0].mid) {
+			unsigned x = mdb_mid2l_search(dl, pgno);
+			if (x <= dl[0].mid && dl[x].mid == pgno) {
+				if (mp != dl[x].mptr) { // bad cursor?
+					mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+					txn->mt_flags |= MDB_TXN_ERROR;
+					return MDB_CORRUPTED;
+				}
+				return 0;
+			}
+		}
+		mdb_cassert(mc, dl[0].mid < MDB_IDL_UM_MAX);
+		// No - copy it
+		np = mdb_page_malloc(txn, 1);
+		if (!np)
+			return ENOMEM;
+		mid.mid = pgno;
+		mid.mptr = np;
+		rc = mdb_mid2l_insert(dl, &mid);
+		mdb_cassert(mc, rc == 0);
+	} else {
+		return 0;
+	}
+
+	mdb_page_copy(np, mp, txn->mt_env->me_psize);
+	np->mp_pgno = pgno;
+	np->mp_flags |= P_DIRTY;
+
+done:
+	// Adjust cursors pointing to mp
+	mc->mc_pg[mc->mc_top] = np;
+	m2 = txn->mt_cursors[mc->mc_dbi];
+	if (mc->mc_flags & C_SUB) {
+		for (; m2; m2=m2->mc_next) {
+			m3 = &m2->mc_xcursor->mx_cursor;
+			if (m3->mc_snum < mc->mc_snum) continue;
+			if (m3->mc_pg[mc->mc_top] == mp)
+				m3->mc_pg[mc->mc_top] = np;
+		}
+	} else {
+		for (; m2; m2=m2->mc_next) {
+			if (m2->mc_snum < mc->mc_snum) continue;
+			if (m2->mc_pg[mc->mc_top] == mp) {
+				m2->mc_pg[mc->mc_top] = np;
+				if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
+					m2->mc_ki[mc->mc_top] == mc->mc_ki[mc->mc_top])
+				{
+					MDB_node *leaf = NODEPTR(np, mc->mc_ki[mc->mc_top]);
+					if (!(leaf->mn_flags & F_SUBDATA))
+						m2->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+				}
+			}
+		}
+	}
+	return 0;
+
+fail:
+	txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+	*/
+
+	return 0
+}
+
+// Search for key within a page, using binary search.
+// Returns the smallest entry larger or equal to the key.
+// If exactp is non-null, stores whether the found entry was an exact match
+// in *exactp (1 or 0).
+// Updates the cursor index with the index of the found entry.
+// If no entry larger or equal to the key is found, returns NULL.
+func (c *cursor) search(key []byte) (*node, bool) {
+	/*
+	unsigned int	 i = 0, nkeys;
+	int		 low, high;
+	int		 rc = 0;
+	MDB_page *mp = mc->mc_pg[mc->mc_top];
+	MDB_node	*node = NULL;
+	MDB_val	 nodekey;
+	MDB_cmp_func *cmp;
+	DKBUF;
+
+	nkeys = NUMKEYS(mp);
+
+	DPRINTF(("searching %u keys in %s %spage %"Z"u",
+	    nkeys, IS_LEAF(mp) ? "leaf" : "branch", IS_SUBP(mp) ? "sub-" : "",
+	    mdb_dbg_pgno(mp)));
+
+	low = IS_LEAF(mp) ? 0 : 1;
+	high = nkeys - 1;
+	cmp = mc->mc_dbx->md_cmp;
+
+	// Branch pages have no data, so if using integer keys,
+	// alignment is guaranteed. Use faster mdb_cmp_int.
+	if (cmp == mdb_cmp_cint && IS_BRANCH(mp)) {
+		if (NODEPTR(mp, 1)->mn_ksize == sizeof(size_t))
+			cmp = mdb_cmp_long;
+		else
+			cmp = mdb_cmp_int;
+	}
+
+	if (IS_LEAF2(mp)) {
+		nodekey.mv_size = mc->mc_db->md_pad;
+		node = NODEPTR(mp, 0);	// fake
+		while (low <= high) {
+			i = (low + high) >> 1;
+			nodekey.mv_data = LEAF2KEY(mp, i, nodekey.mv_size);
+			rc = cmp(key, &nodekey);
+			DPRINTF(("found leaf index %u [%s], rc = %i",
+			    i, DKEY(&nodekey), rc));
+			if (rc == 0)
+				break;
+			if (rc > 0)
+				low = i + 1;
+			else
+				high = i - 1;
+		}
+	} else {
+		while (low <= high) {
+			i = (low + high) >> 1;
+
+			node = NODEPTR(mp, i);
+			nodekey.mv_size = NODEKSZ(node);
+			nodekey.mv_data = NODEKEY(node);
+
+			rc = cmp(key, &nodekey);
+#if MDB_DEBUG
+			if (IS_LEAF(mp))
+				DPRINTF(("found leaf index %u [%s], rc = %i",
+				    i, DKEY(&nodekey), rc));
+			else
+				DPRINTF(("found branch index %u [%s -> %"Z"u], rc = %i",
+				    i, DKEY(&nodekey), NODEPGNO(node), rc));
+#endif
+			if (rc == 0)
+				break;
+			if (rc > 0)
+				low = i + 1;
+			else
+				high = i - 1;
+		}
+	}
+
+	if (rc > 0) {	// Found entry is less than the key.
+		i++;	// Skip to get the smallest entry larger than key.
+		if (!IS_LEAF2(mp))
+			node = NODEPTR(mp, i);
+	}
+	if (exactp)
+		*exactp = (rc == 0 && nkeys > 0);
+	// store the key index
+	mc->mc_ki[mc->mc_top] = i;
+	if (i >= nkeys)
+		// There is no entry larger or equal to the key.
+		return NULL;
+
+	// nodeptr is fake for LEAF2
+	return node;
+	*/
+	return nil, false
+}
+
+func (c *cursor) pop() {
+	/*
+	if (mc->mc_snum) {
+#if MDB_DEBUG
+		MDB_page	*top = mc->mc_pg[mc->mc_top];
+#endif
+		mc->mc_snum--;
+		if (mc->mc_snum)
+			mc->mc_top--;
+
+		DPRINTF(("popped page %"Z"u off db %d cursor %p", top->mp_pgno,
+			DDBI(mc), (void *) mc));
+	}
+	*/
+}
+
+/** Push a page onto the top of the cursor's stack. */
+func (c *cursor) push(p *page) error {
+	/*
+	DPRINTF(("pushing page %"Z"u on db %d cursor %p", mp->mp_pgno,
+		DDBI(mc), (void *) mc));
+
+	if (mc->mc_snum >= CURSOR_STACK) {
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_CURSOR_FULL;
+	}
+
+	mc->mc_top = mc->mc_snum++;
+	mc->mc_pg[mc->mc_top] = mp;
+	mc->mc_ki[mc->mc_top] = 0;
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Finish #mdb_page_search() / #mdb_page_search_lowest().
+// The cursor is at the root page, set up the rest of it.
+func (c *cursor) searchRoot(key []byte, flags int) error {
+	/*
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	int rc;
+	DKBUF;
+
+	while (IS_BRANCH(mp)) {
+		MDB_node	*node;
+		indx_t		i;
+
+		DPRINTF(("branch page %"Z"u has %u keys", mp->mp_pgno, NUMKEYS(mp)));
+		mdb_cassert(mc, NUMKEYS(mp) > 1);
+		DPRINTF(("found index 0 to page %"Z"u", NODEPGNO(NODEPTR(mp, 0))));
+
+		if (flags & (MDB_PS_FIRST|MDB_PS_LAST)) {
+			i = 0;
+			if (flags & MDB_PS_LAST)
+				i = NUMKEYS(mp) - 1;
+		} else {
+			int	 exact;
+			node = mdb_node_search(mc, key, &exact);
+			if (node == NULL)
+				i = NUMKEYS(mp) - 1;
+			else {
+				i = mc->mc_ki[mc->mc_top];
+				if (!exact) {
+					mdb_cassert(mc, i > 0);
+					i--;
+				}
+			}
+			DPRINTF(("following index %u for key [%s]", i, DKEY(key)));
+		}
+
+		mdb_cassert(mc, i < NUMKEYS(mp));
+		node = NODEPTR(mp, i);
+
+		if ((rc = mdb_page_get(mc->mc_txn, NODEPGNO(node), &mp, NULL)) != 0)
+			return rc;
+
+		mc->mc_ki[mc->mc_top] = i;
+		if ((rc = mdb_cursor_push(mc, mp)))
+			return rc;
+
+		if (flags & MDB_PS_MODIFY) {
+			if ((rc = mdb_page_touch(mc)) != 0)
+				return rc;
+			mp = mc->mc_pg[mc->mc_top];
+		}
+	}
+
+	if (!IS_LEAF(mp)) {
+		DPRINTF(("internal error, index points to a %02X page!?",
+		    mp->mp_flags));
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_CORRUPTED;
+	}
+
+	DPRINTF(("found leaf page %"Z"u for key [%s]", mp->mp_pgno,
+	    key ? DKEY(key) : "null"));
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Search for the lowest key under the current branch page.
+// This just bypasses a NUMKEYS check in the current page
+// before calling mdb_page_search_root(), because the callers
+// are all in situations where the current page is known to
+// be underfilled.
+func (c *cursor) searchLowest() error {
+	/*
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	MDB_node	*node = NODEPTR(mp, 0);
+	int rc;
+
+	if ((rc = mdb_page_get(mc->mc_txn, NODEPGNO(node), &mp, NULL)) != 0)
+		return rc;
+
+	mc->mc_ki[mc->mc_top] = 0;
+	if ((rc = mdb_cursor_push(mc, mp)))
+		return rc;
+	return mdb_page_search_root(mc, NULL, MDB_PS_FIRST);
+	*/
+}
+
+// Search for the page a given key should be in.
+// Push it and its parent pages on the cursor stack.
+// @param[in,out] mc the cursor for this operation.
+// @param[in] key the key to search for, or NULL for first/last page.
+// @param[in] flags If MDB_PS_MODIFY is set, visited pages in the DB
+//   are touched (updated with new page numbers).
+//   If MDB_PS_FIRST or MDB_PS_LAST is set, find first or last leaf.
+//   This is used by #mdb_cursor_first() and #mdb_cursor_last().
+//   If MDB_PS_ROOTONLY set, just fetch root node, no further lookups.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) findPage(key []byte, flags int) error {
+	/*
+	int		 rc;
+	pgno_t		 root;
+
+	// Make sure the txn is still viable, then find the root from
+	// the txn's db table and set it as the root of the cursor's stack.
+	if (F_ISSET(mc->mc_txn->mt_flags, MDB_TXN_ERROR)) {
+		DPUTS("transaction has failed, must abort");
+		return MDB_BAD_TXN;
+	} else {
+		// Make sure we're using an up-to-date root
+		if (*mc->mc_dbflag & DB_STALE) {
+				MDB_cursor mc2;
+				mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, NULL);
+				rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, 0);
+				if (rc)
+					return rc;
+				{
+					MDB_val data;
+					int exact = 0;
+					uint16_t flags;
+					MDB_node *leaf = mdb_node_search(&mc2,
+						&mc->mc_dbx->md_name, &exact);
+					if (!exact)
+						return MDB_NOTFOUND;
+					rc = mdb_node_read(mc->mc_txn, leaf, &data);
+					if (rc)
+						return rc;
+					memcpy(&flags, ((char *) data.mv_data + offsetof(MDB_db, md_flags)),
+						sizeof(uint16_t));
+					// The txn may not know this DBI, or another process may
+					// have dropped and recreated the DB with other flags.
+					if ((mc->mc_db->md_flags & PERSISTENT_FLAGS) != flags)
+						return MDB_INCOMPATIBLE;
+					memcpy(mc->mc_db, data.mv_data, sizeof(MDB_db));
+				}
+				*mc->mc_dbflag &= ~DB_STALE;
+		}
+		root = mc->mc_db->md_root;
+
+		if (root == P_INVALID) {		// Tree is empty.
+			DPUTS("tree is empty");
+			return MDB_NOTFOUND;
+		}
+	}
+
+	mdb_cassert(mc, root > 1);
+	if (!mc->mc_pg[0] || mc->mc_pg[0]->mp_pgno != root)
+		if ((rc = mdb_page_get(mc->mc_txn, root, &mc->mc_pg[0], NULL)) != 0)
+			return rc;
+
+	mc->mc_snum = 1;
+	mc->mc_top = 0;
+
+	DPRINTF(("db %d root page %"Z"u has flags 0x%X",
+		DDBI(mc), root, mc->mc_pg[0]->mp_flags));
+
+	if (flags & MDB_PS_MODIFY) {
+		if ((rc = mdb_page_touch(mc)))
+			return rc;
+	}
+
+	if (flags & MDB_PS_ROOTONLY)
+		return MDB_SUCCESS;
+
+	return mdb_page_search_root(mc, key, flags);
+	*/
+	return nil
+}
+
+func (c *cursor) freeOverflowPage(p *page) error {
+	/*
+	MDB_txn *txn = mc->mc_txn;
+	pgno_t pg = mp->mp_pgno;
+	unsigned x = 0, ovpages = mp->mp_pages;
+	MDB_env *env = txn->mt_env;
+	MDB_IDL sl = txn->mt_spill_pgs;
+	MDB_ID pn = pg << 1;
+	int rc;
+
+	DPRINTF(("free ov page %"Z"u (%d)", pg, ovpages));
+	// If the page is dirty or on the spill list we just acquired it,
+	// so we should give it back to our current free list, if any.
+	// Otherwise put it onto the list of pages we freed in this txn.
+	//
+	// Won't create me_pghead: me_pglast must be inited along with it.
+	// Unsupported in nested txns: They would need to hide the page
+	// range in ancestor txns' dirty and spilled lists.
+	if (env->me_pghead &&
+		!txn->mt_parent &&
+		((mp->mp_flags & P_DIRTY) ||
+		 (sl && (x = mdb_midl_search(sl, pn)) <= sl[0] && sl[x] == pn)))
+	{
+		unsigned i, j;
+		pgno_t *mop;
+		MDB_ID2 *dl, ix, iy;
+		rc = mdb_midl_need(&env->me_pghead, ovpages);
+		if (rc)
+			return rc;
+		if (!(mp->mp_flags & P_DIRTY)) {
+			// This page is no longer spilled
+			if (x == sl[0])
+				sl[0]--;
+			else
+				sl[x] |= 1;
+			goto release;
+		}
+		// Remove from dirty list
+		dl = txn->mt_u.dirty_list;
+		x = dl[0].mid--;
+		for (ix = dl[x]; ix.mptr != mp; ix = iy) {
+			if (x > 1) {
+				x--;
+				iy = dl[x];
+				dl[x] = ix;
+			} else {
+				mdb_cassert(mc, x > 1);
+				j = ++(dl[0].mid);
+				dl[j] = ix;		// Unsorted. OK when MDB_TXN_ERROR.
+				txn->mt_flags |= MDB_TXN_ERROR;
+				return MDB_CORRUPTED;
+			}
+		}
+		if (!(env->me_flags & MDB_WRITEMAP))
+			mdb_dpage_free(env, mp);
+release:
+		// Insert in me_pghead
+		mop = env->me_pghead;
+		j = mop[0] + ovpages;
+		for (i = mop[0]; i && mop[i] < pg; i--)
+			mop[j--] = mop[i];
+		while (j>i)
+			mop[j--] = pg++;
+		mop[0] += ovpages;
+	} else {
+		rc = mdb_midl_append_range(&txn->mt_free_pgs, pg, ovpages);
+		if (rc)
+			return rc;
+	}
+	mc->mc_db->md_overflow_pages -= ovpages;
+	return 0;
+	*/
+	return nil
+}
+
+
+// Find a sibling for a page.
+// Replaces the page at the top of the cursor's stack with the
+// specified sibling, if one exists.
+// @param[in] mc The cursor for this operation.
+// @param[in] move_right Non-zero if the right sibling is requested,
+// otherwise the left sibling.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) sibling(moveRight bool) error {
+	/*
+	int		 rc;
+	MDB_node	*indx;
+	MDB_page	*mp;
+
+	if (mc->mc_snum < 2) {
+		return MDB_NOTFOUND;		// root has no siblings
+	}
+
+	mdb_cursor_pop(mc);
+	DPRINTF(("parent page is page %"Z"u, index %u",
+		mc->mc_pg[mc->mc_top]->mp_pgno, mc->mc_ki[mc->mc_top]));
+
+	if (move_right ? (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mc->mc_pg[mc->mc_top]))
+		       : (mc->mc_ki[mc->mc_top] == 0)) {
+		DPRINTF(("no more keys left, moving to %s sibling",
+		    move_right ? "right" : "left"));
+		if ((rc = mdb_cursor_sibling(mc, move_right)) != MDB_SUCCESS) {
+			// undo cursor_pop before returning
+			mc->mc_top++;
+			mc->mc_snum++;
+			return rc;
+		}
+	} else {
+		if (move_right)
+			mc->mc_ki[mc->mc_top]++;
+		else
+			mc->mc_ki[mc->mc_top]--;
+		DPRINTF(("just moving to %s index key %u",
+		    move_right ? "right" : "left", mc->mc_ki[mc->mc_top]));
+	}
+	mdb_cassert(mc, IS_BRANCH(mc->mc_pg[mc->mc_top]));
+
+	indx = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+	if ((rc = mdb_page_get(mc->mc_txn, NODEPGNO(indx), &mp, NULL)) != 0) {
+		// mc will be inconsistent if caller does mc_snum++ as above
+		mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+		return rc;
+	}
+
+	mdb_cursor_push(mc, mp);
+	if (!move_right)
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mp)-1;
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Move the cursor to the next data item.
+func (c *cursor) next(key []byte, data []byte, op int) error {
+	/*
+	MDB_page	*mp;
+	MDB_node	*leaf;
+	int rc;
+
+	if (mc->mc_flags & C_EOF) {
+		return MDB_NOTFOUND;
+	}
+
+	mdb_cassert(mc, mc->mc_flags & C_INITIALIZED);
+
+	mp = mc->mc_pg[mc->mc_top];
+
+	if (mc->mc_db->md_flags & MDB_DUPSORT) {
+		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_NEXT || op == MDB_NEXT_DUP) {
+				rc = mdb_cursor_next(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_NEXT);
+				if (op != MDB_NEXT || rc != MDB_NOTFOUND) {
+					if (rc == MDB_SUCCESS)
+						MDB_GET_KEY(leaf, key);
+					return rc;
+				}
+			}
+		} else {
+			mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+			if (op == MDB_NEXT_DUP)
+				return MDB_NOTFOUND;
+		}
+	}
+
+	DPRINTF(("cursor_next: top page is %"Z"u in cursor %p",
+		mdb_dbg_pgno(mp), (void *) mc));
+	if (mc->mc_flags & C_DEL)
+		goto skip;
+
+	if (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mp)) {
+		DPUTS("=====> move to next sibling page");
+		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS) {
+			mc->mc_flags |= C_EOF;
+			return rc;
+		}
+		mp = mc->mc_pg[mc->mc_top];
+		DPRINTF(("next page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
+	} else
+		mc->mc_ki[mc->mc_top]++;
+
+skip:
+	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
+	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
+
+	if (IS_LEAF2(mp)) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	mdb_cassert(mc, IS_LEAF(mp));
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if ((rc = mdb_node_read(mc->mc_txn, leaf, data)) != MDB_SUCCESS)
+			return rc;
+
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Move the cursor to the previous data item.
+func (c *cursor) prev(key []byte, data []byte, op int) error {
+	/*
+	MDB_page	*mp;
+	MDB_node	*leaf;
+	int rc;
+
+	mdb_cassert(mc, mc->mc_flags & C_INITIALIZED);
+
+	mp = mc->mc_pg[mc->mc_top];
+
+	if (mc->mc_db->md_flags & MDB_DUPSORT) {
+		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_PREV || op == MDB_PREV_DUP) {
+				rc = mdb_cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_PREV);
+				if (op != MDB_PREV || rc != MDB_NOTFOUND) {
+					if (rc == MDB_SUCCESS)
+						MDB_GET_KEY(leaf, key);
+					return rc;
+				}
+			} else {
+				mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+				if (op == MDB_PREV_DUP)
+					return MDB_NOTFOUND;
+			}
+		}
+	}
+
+	DPRINTF(("cursor_prev: top page is %"Z"u in cursor %p",
+		mdb_dbg_pgno(mp), (void *) mc));
+
+	if (mc->mc_ki[mc->mc_top] == 0)  {
+		DPUTS("=====> move to prev sibling page");
+		if ((rc = mdb_cursor_sibling(mc, 0)) != MDB_SUCCESS) {
+			return rc;
+		}
+		mp = mc->mc_pg[mc->mc_top];
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mp) - 1;
+		DPRINTF(("prev page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
+	} else
+		mc->mc_ki[mc->mc_top]--;
+
+	mc->mc_flags &= ~C_EOF;
+
+	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
+	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
+
+	if (IS_LEAF2(mp)) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	mdb_cassert(mc, IS_LEAF(mp));
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if ((rc = mdb_node_read(mc->mc_txn, leaf, data)) != MDB_SUCCESS)
+			return rc;
+
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+	*/
+}
+
+// Set the cursor on a specific data item.
+// (bool return is whether it is exact).
+func (c *cursor) set(key []byte, data []byte, op int) (error, bool) {
+	/*
+	int		 rc;
+	MDB_page	*mp;
+	MDB_node	*leaf = NULL;
+	DKBUF;
+
+	if (key->mv_size == 0)
+		return MDB_BAD_VALSIZE;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	// See if we're already on the right page
+	if (mc->mc_flags & C_INITIALIZED) {
+		MDB_val nodekey;
+
+		mp = mc->mc_pg[mc->mc_top];
+		if (!NUMKEYS(mp)) {
+			mc->mc_ki[mc->mc_top] = 0;
+			return MDB_NOTFOUND;
+		}
+		if (mp->mp_flags & P_LEAF2) {
+			nodekey.mv_size = mc->mc_db->md_pad;
+			nodekey.mv_data = LEAF2KEY(mp, 0, nodekey.mv_size);
+		} else {
+			leaf = NODEPTR(mp, 0);
+			MDB_GET_KEY2(leaf, nodekey);
+		}
+		rc = mc->mc_dbx->md_cmp(key, &nodekey);
+		if (rc == 0) {
+			// Probably happens rarely, but first node on the page
+			// was the one we wanted.
+			mc->mc_ki[mc->mc_top] = 0;
+			if (exactp)
+				*exactp = 1;
+			goto set1;
+		}
+		if (rc > 0) {
+			unsigned int i;
+			unsigned int nkeys = NUMKEYS(mp);
+			if (nkeys > 1) {
+				if (mp->mp_flags & P_LEAF2) {
+					nodekey.mv_data = LEAF2KEY(mp,
+						 nkeys-1, nodekey.mv_size);
+				} else {
+					leaf = NODEPTR(mp, nkeys-1);
+					MDB_GET_KEY2(leaf, nodekey);
+				}
+				rc = mc->mc_dbx->md_cmp(key, &nodekey);
+				if (rc == 0) {
+					// last node was the one we wanted
+					mc->mc_ki[mc->mc_top] = nkeys-1;
+					if (exactp)
+						*exactp = 1;
+					goto set1;
+				}
+				if (rc < 0) {
+					if (mc->mc_ki[mc->mc_top] < NUMKEYS(mp)) {
+						// This is definitely the right page, skip search_page 
+						if (mp->mp_flags & P_LEAF2) {
+							nodekey.mv_data = LEAF2KEY(mp,
+								 mc->mc_ki[mc->mc_top], nodekey.mv_size);
+						} else {
+							leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+							MDB_GET_KEY2(leaf, nodekey);
+						}
+						rc = mc->mc_dbx->md_cmp(key, &nodekey);
+						if (rc == 0) {
+							// current node was the one we wanted
+							if (exactp)
+								*exactp = 1;
+							goto set1;
+						}
+					}
+					rc = 0;
+					goto set2;
+				}
+			}
+			// If any parents have right-sibs, search.
+			// Otherwise, there's nothing further.
+			for (i=0; i<mc->mc_top; i++)
+				if (mc->mc_ki[i] <
+					NUMKEYS(mc->mc_pg[i])-1)
+					break;
+			if (i == mc->mc_top) {
+				// There are no other pages
+				mc->mc_ki[mc->mc_top] = nkeys;
+				return MDB_NOTFOUND;
+			}
+		}
+		if (!mc->mc_top) {
+			// There are no other pages
+			mc->mc_ki[mc->mc_top] = 0;
+			if (op == MDB_SET_RANGE) {
+				rc = 0;
+				goto set1;
+			} else
+				return MDB_NOTFOUND;
+		}
+	}
+
+	rc = mdb_page_search(mc, key, 0);
+	if (rc != MDB_SUCCESS)
+		return rc;
+
+	mp = mc->mc_pg[mc->mc_top];
+	mdb_cassert(mc, IS_LEAF(mp));
+
+set2:
+	leaf = mdb_node_search(mc, key, exactp);
+	if (exactp != NULL && !*exactp) {
+		// MDB_SET specified and not an exact match.
+		return MDB_NOTFOUND;
+	}
+
+	if (leaf == NULL) {
+		DPUTS("===> inexact leaf not found, goto sibling");
+		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS)
+			return rc;		// no entries matched
+		mp = mc->mc_pg[mc->mc_top];
+		mdb_cassert(mc, IS_LEAF(mp));
+		leaf = NODEPTR(mp, 0);
+	}
+
+set1:
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	if (IS_LEAF2(mp)) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_SET || op == MDB_SET_KEY || op == MDB_SET_RANGE) {
+				rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			} else {
+				int ex2, *ex2p;
+				if (op == MDB_GET_BOTH) {
+					ex2p = &ex2;
+					ex2 = 0;
+				} else {
+					ex2p = NULL;
+				}
+				rc = mdb_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_SET_RANGE, ex2p);
+				if (rc != MDB_SUCCESS)
+					return rc;
+			}
+		} else if (op == MDB_GET_BOTH || op == MDB_GET_BOTH_RANGE) {
+			MDB_val d2;
+			if ((rc = mdb_node_read(mc->mc_txn, leaf, &d2)) != MDB_SUCCESS)
+				return rc;
+			rc = mc->mc_dbx->md_dcmp(data, &d2);
+			if (rc) {
+				if (op == MDB_GET_BOTH || rc > 0)
+					return MDB_NOTFOUND;
+				rc = 0;
+				*data = d2;
+			}
+
+		} else {
+			if (mc->mc_xcursor)
+				mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+			if ((rc = mdb_node_read(mc->mc_txn, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	// The key already matches in all other cases
+	if (op == MDB_SET_RANGE || op == MDB_SET_KEY)
+		MDB_GET_KEY(leaf, key);
+	DPRINTF(("==> cursor placed on key [%s]", DKEY(key)));
+
+	return rc;
+	*/
+
+	return nil
+}
+
+// Move the cursor to the first item in the database.
+func (c *cursor) first(key []byte, data []byte) error {
+	/*
+	int		 rc;
+	MDB_node	*leaf;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+		rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
+		if (rc != MDB_SUCCESS)
+			return rc;
+	}
+	mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], 0);
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	mc->mc_ki[mc->mc_top] = 0;
+
+	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], 0, key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			mdb_xcursor_init1(mc, leaf);
+			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc)
+				return rc;
+		} else {
+			if ((rc = mdb_node_read(mc->mc_txn, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Move the cursor to the last item in the database.
+func (c *cursor) last() ([]byte, []byte) {
+	int		 rc;
+	MDB_node	*leaf;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	if (!(mc->mc_flags & C_EOF)) {
+
+		if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+			rc = mdb_page_search(mc, NULL, MDB_PS_LAST);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+		mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+
+	}
+	mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]) - 1;
+	mc->mc_flags |= C_INITIALIZED|C_EOF;
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+
+	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			mdb_xcursor_init1(mc, leaf);
+			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc)
+				return rc;
+		} else {
+			if ((rc = mdb_node_read(mc->mc_txn, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+}
+
+func (c *cursor) Get(key []byte, data []byte, op int) ([]byte, []byte, error) {
+	/*
+	int		 rc;
+	int		 exact = 0;
+	int		 (*mfunc)(MDB_cursor *mc, MDB_val *key, MDB_val *data);
+
+	if (mc == NULL)
+		return EINVAL;
+
+	if (mc->mc_txn->mt_flags & MDB_TXN_ERROR)
+		return MDB_BAD_TXN;
+
+	switch (op) {
+	case MDB_GET_CURRENT:
+		if (!(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+		} else {
+			MDB_page *mp = mc->mc_pg[mc->mc_top];
+			int nkeys = NUMKEYS(mp);
+			if (!nkeys || mc->mc_ki[mc->mc_top] >= nkeys) {
+				mc->mc_ki[mc->mc_top] = nkeys;
+				rc = MDB_NOTFOUND;
+				break;
+			}
+			rc = MDB_SUCCESS;
+			if (IS_LEAF2(mp)) {
+				key->mv_size = mc->mc_db->md_pad;
+				key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+			} else {
+				MDB_node *leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+				MDB_GET_KEY(leaf, key);
+				if (data) {
+					if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+						if (mc->mc_flags & C_DEL)
+							mdb_xcursor_init1(mc, leaf);
+						rc = mdb_cursor_get(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_GET_CURRENT);
+					} else {
+						rc = mdb_node_read(mc->mc_txn, leaf, data);
+					}
+				}
+			}
+		}
+		break;
+	case MDB_GET_BOTH:
+	case MDB_GET_BOTH_RANGE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (mc->mc_xcursor == NULL) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		// FALLTHRU
+	case MDB_SET:
+	case MDB_SET_KEY:
+	case MDB_SET_RANGE:
+		if (key == NULL) {
+			rc = EINVAL;
+		} else {
+			rc = mdb_cursor_set(mc, key, data, op,
+				op == MDB_SET_RANGE ? NULL : &exact);
+		}
+		break;
+	case MDB_GET_MULTIPLE:
+		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		rc = MDB_SUCCESS;
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) ||
+			(mc->mc_xcursor->mx_cursor.mc_flags & C_EOF))
+			break;
+		goto fetchm;
+	case MDB_NEXT_MULTIPLE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		if (!(mc->mc_flags & C_INITIALIZED))
+			rc = mdb_cursor_first(mc, key, data);
+		else
+			rc = mdb_cursor_next(mc, key, data, MDB_NEXT_DUP);
+		if (rc == MDB_SUCCESS) {
+			if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+				MDB_cursor *mx;
+fetchm:
+				mx = &mc->mc_xcursor->mx_cursor;
+				data->mv_size = NUMKEYS(mx->mc_pg[mx->mc_top]) *
+					mx->mc_db->md_pad;
+				data->mv_data = METADATA(mx->mc_pg[mx->mc_top]);
+				mx->mc_ki[mx->mc_top] = NUMKEYS(mx->mc_pg[mx->mc_top])-1;
+			} else {
+				rc = MDB_NOTFOUND;
+			}
+		}
+		break;
+	case MDB_NEXT:
+	case MDB_NEXT_DUP:
+	case MDB_NEXT_NODUP:
+		if (!(mc->mc_flags & C_INITIALIZED))
+			rc = mdb_cursor_first(mc, key, data);
+		else
+			rc = mdb_cursor_next(mc, key, data, op);
+		break;
+	case MDB_PREV:
+	case MDB_PREV_DUP:
+	case MDB_PREV_NODUP:
+		if (!(mc->mc_flags & C_INITIALIZED)) {
+			rc = mdb_cursor_last(mc, key, data);
+			if (rc)
+				break;
+			mc->mc_flags |= C_INITIALIZED;
+			mc->mc_ki[mc->mc_top]++;
+		}
+		rc = mdb_cursor_prev(mc, key, data, op);
+		break;
+	case MDB_FIRST:
+		rc = mdb_cursor_first(mc, key, data);
+		break;
+	case MDB_FIRST_DUP:
+		mfunc = mdb_cursor_first;
+	mmove:
+		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		if (mc->mc_xcursor == NULL) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		rc = mfunc(&mc->mc_xcursor->mx_cursor, data, NULL);
+		break;
+	case MDB_LAST:
+		rc = mdb_cursor_last(mc, key, data);
+		break;
+	case MDB_LAST_DUP:
+		mfunc = mdb_cursor_last;
+		goto mmove;
+	default:
+		DPRINTF(("unhandled/unimplemented cursor operation %u", op));
+		rc = EINVAL;
+		break;
+	}
+
+	if (mc->mc_flags & C_DEL)
+		mc->mc_flags ^= C_DEL;
+
+	return rc;
+	*/
+	return nil, nil, nil
+}
+
+// Touch all the pages in the cursor stack. Set mc_top.
+//	Makes sure all the pages are writable, before attempting a write operation.
+// @param[in] mc The cursor to operate on.
+func (c *cursor) touch() error {
+	/*
+	int rc = MDB_SUCCESS;
+
+	if (mc->mc_dbi > MAIN_DBI && !(*mc->mc_dbflag & DB_DIRTY)) {
+		MDB_cursor mc2;
+		MDB_xcursor mcx;
+		mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, &mcx);
+		rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, MDB_PS_MODIFY);
+		if (rc)
+			 return rc;
+		*mc->mc_dbflag |= DB_DIRTY;
+	}
+	mc->mc_top = 0;
+	if (mc->mc_snum) {
+		do {
+			rc = mdb_page_touch(mc);
+		} while (!rc && ++(mc->mc_top) < mc->mc_snum);
+		mc->mc_top = mc->mc_snum-1;
+	}
+	return rc;
+}
+
+int
+mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
+    unsigned int flags)
+{
+	enum { MDB_NO_ROOT = MDB_LAST_ERRCODE+10 }; // internal code
+	MDB_env		*env;
+	MDB_node	*leaf = NULL;
+	MDB_page	*fp, *mp;
+	uint16_t	fp_flags;
+	MDB_val		xdata, *rdata, dkey, olddata;
+	MDB_db dummy;
+	int do_sub = 0, insert;
+	unsigned int mcount = 0, dcount = 0, nospill;
+	size_t nsize;
+	int rc, rc2;
+	unsigned int nflags;
+	DKBUF;
+
+	if (mc == NULL || key == NULL)
+		return EINVAL;
+
+	env = mc->mc_txn->mt_env;
+
+	// Check this first so counter will always be zero on any
+	// early failures.
+	if (flags & MDB_MULTIPLE) {
+		dcount = data[1].mv_size;
+		data[1].mv_size = 0;
+		if (!F_ISSET(mc->mc_db->md_flags, MDB_DUPFIXED))
+			return MDB_INCOMPATIBLE;
+	}
+
+	nospill = flags & MDB_NOSPILL;
+	flags &= ~MDB_NOSPILL;
+
+	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_ERROR))
+		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	if (flags != MDB_CURRENT && key->mv_size-1 >= ENV_MAXKEY(env))
+		return MDB_BAD_VALSIZE;
+
+#if SIZE_MAX > MAXDATASIZE
+	if (data->mv_size > ((mc->mc_db->md_flags & MDB_DUPSORT) ? ENV_MAXKEY(env) : MAXDATASIZE))
+		return MDB_BAD_VALSIZE;
+#else
+	if ((mc->mc_db->md_flags & MDB_DUPSORT) && data->mv_size > ENV_MAXKEY(env))
+		return MDB_BAD_VALSIZE;
+#endif
+
+	DPRINTF(("==> put db %d key [%s], size %"Z"u, data size %"Z"u",
+		DDBI(mc), DKEY(key), key ? key->mv_size : 0, data->mv_size));
+
+	dkey.mv_size = 0;
+
+	if (flags == MDB_CURRENT) {
+		if (!(mc->mc_flags & C_INITIALIZED))
+			return EINVAL;
+		rc = MDB_SUCCESS;
+	} else if (mc->mc_db->md_root == P_INVALID) {
+		// new database, cursor has nothing to point to
+		mc->mc_snum = 0;
+		mc->mc_top = 0;
+		mc->mc_flags &= ~C_INITIALIZED;
+		rc = MDB_NO_ROOT;
+	} else {
+		int exact = 0;
+		MDB_val d2;
+		if (flags & MDB_APPEND) {
+			MDB_val k2;
+			rc = mdb_cursor_last(mc, &k2, &d2);
+			if (rc == 0) {
+				rc = mc->mc_dbx->md_cmp(key, &k2);
+				if (rc > 0) {
+					rc = MDB_NOTFOUND;
+					mc->mc_ki[mc->mc_top]++;
+				} else {
+					// new key is <= last key
+					rc = MDB_KEYEXIST;
+				}
+			}
+		} else {
+			rc = mdb_cursor_set(mc, key, &d2, MDB_SET, &exact);
+		}
+		if ((flags & MDB_NOOVERWRITE) && rc == 0) {
+			DPRINTF(("duplicate key [%s]", DKEY(key)));
+			*data = d2;
+			return MDB_KEYEXIST;
+		}
+		if (rc && rc != MDB_NOTFOUND)
+			return rc;
+	}
+
+	if (mc->mc_flags & C_DEL)
+		mc->mc_flags ^= C_DEL;
+
+	// Cursor is positioned, check for room in the dirty list
+	if (!nospill) {
+		if (flags & MDB_MULTIPLE) {
+			rdata = &xdata;
+			xdata.mv_size = data->mv_size * dcount;
+		} else {
+			rdata = data;
+		}
+		if ((rc2 = mdb_page_spill(mc, key, rdata)))
+			return rc2;
+	}
+
+	if (rc == MDB_NO_ROOT) {
+		MDB_page *np;
+		// new database, write a root leaf page
+		DPUTS("allocating new root leaf page");
+		if ((rc2 = mdb_page_new(mc, P_LEAF, 1, &np))) {
+			return rc2;
+		}
+		mdb_cursor_push(mc, np);
+		mc->mc_db->md_root = np->mp_pgno;
+		mc->mc_db->md_depth++;
+		*mc->mc_dbflag |= DB_DIRTY;
+		if ((mc->mc_db->md_flags & (MDB_DUPSORT|MDB_DUPFIXED))
+			== MDB_DUPFIXED)
+			np->mp_flags |= P_LEAF2;
+		mc->mc_flags |= C_INITIALIZED;
+	} else {
+		// make sure all cursor pages are writable
+		rc2 = mdb_cursor_touch(mc);
+		if (rc2)
+			return rc2;
+	}
+
+	insert = rc;
+	if (insert) {
+		// The key does not exist
+		DPRINTF(("inserting key at index %i", mc->mc_ki[mc->mc_top]));
+		if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
+			LEAFSIZE(key, data) > env->me_nodemax)
+		{
+			// Too big for a node, insert in sub-DB
+			fp_flags = P_LEAF|P_DIRTY;
+			fp = env->me_pbuf;
+			fp->mp_pad = data->mv_size; // used if MDB_DUPFIXED
+			fp->mp_lower = fp->mp_upper = olddata.mv_size = PAGEHDRSZ;
+			goto prep_subDB;
+		}
+	} else {
+		// there's only a key anyway, so this is a no-op
+		if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+			unsigned int ksize = mc->mc_db->md_pad;
+			if (key->mv_size != ksize)
+				return MDB_BAD_VALSIZE;
+			if (flags == MDB_CURRENT) {
+				char *ptr = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], ksize);
+				memcpy(ptr, key->mv_data, ksize);
+			}
+			return MDB_SUCCESS;
+		}
+
+more:
+		leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+		olddata.mv_size = NODEDSZ(leaf);
+		olddata.mv_data = NODEDATA(leaf);
+
+		// DB has dups?
+		if (F_ISSET(mc->mc_db->md_flags, MDB_DUPSORT)) {
+			// Prepare (sub-)page/sub-DB to accept the new item,
+			// if needed.  fp: old sub-page or a header faking
+			// it.  mp: new (sub-)page.  offset: growth in page
+			// size.  xdata: node data with new page or DB.
+			ssize_t		i, offset = 0;
+			mp = fp = xdata.mv_data = env->me_pbuf;
+			mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
+
+			// Was a single item before, must convert now
+			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+				// Just overwrite the current item
+				if (flags == MDB_CURRENT)
+					goto current;
+
+#if UINT_MAX < SIZE_MAX
+				if (mc->mc_dbx->md_dcmp == mdb_cmp_int && olddata.mv_size == sizeof(size_t))
+#ifdef MISALIGNED_OK
+					mc->mc_dbx->md_dcmp = mdb_cmp_long;
+#else
+					mc->mc_dbx->md_dcmp = mdb_cmp_cint;
+#endif
+#endif
+				// if data matches, skip it
+				if (!mc->mc_dbx->md_dcmp(data, &olddata)) {
+					if (flags & MDB_NODUPDATA)
+						rc = MDB_KEYEXIST;
+					else if (flags & MDB_MULTIPLE)
+						goto next_mult;
+					else
+						rc = MDB_SUCCESS;
+					return rc;
+				}
+
+				// Back up original data item
+				dkey.mv_size = olddata.mv_size;
+				dkey.mv_data = memcpy(fp+1, olddata.mv_data, olddata.mv_size);
+
+				// Make sub-page header for the dup items, with dummy body
+				fp->mp_flags = P_LEAF|P_DIRTY|P_SUBP;
+				fp->mp_lower = PAGEHDRSZ;
+				xdata.mv_size = PAGEHDRSZ + dkey.mv_size + data->mv_size;
+				if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+					fp->mp_flags |= P_LEAF2;
+					fp->mp_pad = data->mv_size;
+					xdata.mv_size += 2 * data->mv_size;	// leave space for 2 more
+				} else {
+					xdata.mv_size += 2 * (sizeof(indx_t) + NODESIZE) +
+						(dkey.mv_size & 1) + (data->mv_size & 1);
+				}
+				fp->mp_upper = xdata.mv_size;
+				olddata.mv_size = fp->mp_upper; // pretend olddata is fp
+			} else if (leaf->mn_flags & F_SUBDATA) {
+				// Data is on sub-DB, just store it
+				flags |= F_DUPDATA|F_SUBDATA;
+				goto put_sub;
+			} else {
+				// Data is on sub-page
+				fp = olddata.mv_data;
+				switch (flags) {
+				default:
+					i = -(ssize_t)SIZELEFT(fp);
+					if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+						offset = i += (ssize_t) EVEN(
+							sizeof(indx_t) + NODESIZE + data->mv_size);
+					} else {
+						i += offset = fp->mp_pad;
+						offset *= 4; // space for 4 more
+					}
+					if (i > 0)
+						break;
+					// FALLTHRU: Sub-page is big enough
+				case MDB_CURRENT:
+					fp->mp_flags |= P_DIRTY;
+					COPY_PGNO(fp->mp_pgno, mp->mp_pgno);
+					mc->mc_xcursor->mx_cursor.mc_pg[0] = fp;
+					flags |= F_DUPDATA;
+					goto put_sub;
+				}
+				xdata.mv_size = olddata.mv_size + offset;
+			}
+
+			fp_flags = fp->mp_flags;
+			if (NODESIZE + NODEKSZ(leaf) + xdata.mv_size > env->me_nodemax) {
+					// Too big for a sub-page, convert to sub-DB
+					fp_flags &= ~P_SUBP;
+prep_subDB:
+					if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+						fp_flags |= P_LEAF2;
+						dummy.md_pad = fp->mp_pad;
+						dummy.md_flags = MDB_DUPFIXED;
+						if (mc->mc_db->md_flags & MDB_INTEGERDUP)
+							dummy.md_flags |= MDB_INTEGERKEY;
+					} else {
+						dummy.md_pad = 0;
+						dummy.md_flags = 0;
+					}
+					dummy.md_depth = 1;
+					dummy.md_branch_pages = 0;
+					dummy.md_leaf_pages = 1;
+					dummy.md_overflow_pages = 0;
+					dummy.md_entries = NUMKEYS(fp);
+					xdata.mv_size = sizeof(MDB_db);
+					xdata.mv_data = &dummy;
+					if ((rc = mdb_page_alloc(mc, 1, &mp)))
+						return rc;
+					offset = env->me_psize - olddata.mv_size;
+					flags |= F_DUPDATA|F_SUBDATA;
+					dummy.md_root = mp->mp_pgno;
+			}
+			if (mp != fp) {
+				mp->mp_flags = fp_flags | P_DIRTY;
+				mp->mp_pad   = fp->mp_pad;
+				mp->mp_lower = fp->mp_lower;
+				mp->mp_upper = fp->mp_upper + offset;
+				if (fp_flags & P_LEAF2) {
+					memcpy(METADATA(mp), METADATA(fp), NUMKEYS(fp) * fp->mp_pad);
+				} else {
+					memcpy((char *)mp + mp->mp_upper, (char *)fp + fp->mp_upper,
+						olddata.mv_size - fp->mp_upper);
+					for (i = NUMKEYS(fp); --i >= 0; )
+						mp->mp_ptrs[i] = fp->mp_ptrs[i] + offset;
+				}
+			}
+
+			rdata = &xdata;
+			flags |= F_DUPDATA;
+			do_sub = 1;
+			if (!insert)
+				mdb_node_del(mc, 0);
+			goto new_sub;
+		}
+current:
+		// overflow page overwrites need special handling
+		if (F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+			MDB_page *omp;
+			pgno_t pg;
+			int level, ovpages, dpages = OVPAGES(data->mv_size, env->me_psize);
+
+			memcpy(&pg, olddata.mv_data, sizeof(pg));
+			if ((rc2 = mdb_page_get(mc->mc_txn, pg, &omp, &level)) != 0)
+				return rc2;
+			ovpages = omp->mp_pages;
+
+			// Is the ov page large enough? 
+			if (ovpages >= dpages) {
+			  if (!(omp->mp_flags & P_DIRTY) &&
+				  (level || (env->me_flags & MDB_WRITEMAP)))
+			  {
+				rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
+				if (rc)
+					return rc;
+				level = 0;		// dirty in this txn or clean 
+			  }
+			  // Is it dirty?
+			  if (omp->mp_flags & P_DIRTY) {
+				// yes, overwrite it. Note in this case we don't
+				// bother to try shrinking the page if the new data
+				// is smaller than the overflow threshold.
+				if (level > 1) {
+					// It is writable only in a parent txn
+					size_t sz = (size_t) env->me_psize * ovpages, off;
+					MDB_page *np = mdb_page_malloc(mc->mc_txn, ovpages);
+					MDB_ID2 id2;
+					if (!np)
+						return ENOMEM;
+					id2.mid = pg;
+					id2.mptr = np;
+					rc = mdb_mid2l_insert(mc->mc_txn->mt_u.dirty_list, &id2);
+					mdb_cassert(mc, rc == 0);
+					if (!(flags & MDB_RESERVE)) {
+						// Copy end of page, adjusting alignment so
+						// compiler may copy words instead of bytes.
+						off = (PAGEHDRSZ + data->mv_size) & -sizeof(size_t);
+						memcpy((size_t *)((char *)np + off),
+							(size_t *)((char *)omp + off), sz - off);
+						sz = PAGEHDRSZ;
+					}
+					memcpy(np, omp, sz); // Copy beginning of page
+					omp = np;
+				}
+				SETDSZ(leaf, data->mv_size);
+				if (F_ISSET(flags, MDB_RESERVE))
+					data->mv_data = METADATA(omp);
+				else
+					memcpy(METADATA(omp), data->mv_data, data->mv_size);
+				goto done;
+			  }
+			}
+			if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS)
+				return rc2;
+		} else if (data->mv_size == olddata.mv_size) {
+			// same size, just replace it. Note that we could
+			// also reuse this node if the new data is smaller,
+			// but instead we opt to shrink the node in that case.
+			if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = olddata.mv_data;
+			else if (data->mv_size)
+				memcpy(olddata.mv_data, data->mv_data, data->mv_size);
+			else
+				memcpy(NODEKEY(leaf), key->mv_data, key->mv_size);
+			goto done;
+		}
+		mdb_node_del(mc, 0);
+		mc->mc_db->md_entries--;
+	}
+
+	rdata = data;
+
+new_sub:
+	nflags = flags & NODE_ADD_FLAGS;
+	nsize = IS_LEAF2(mc->mc_pg[mc->mc_top]) ? key->mv_size : mdb_leaf_size(env, key, rdata);
+	if (SIZELEFT(mc->mc_pg[mc->mc_top]) < nsize) {
+		if (( flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA )
+			nflags &= ~MDB_APPEND;
+		if (!insert)
+			nflags |= MDB_SPLIT_REPLACE;
+		rc = mdb_page_split(mc, key, rdata, P_INVALID, nflags);
+	} else {
+		// There is room already in this leaf page.
+		rc = mdb_node_add(mc, mc->mc_ki[mc->mc_top], key, rdata, 0, nflags);
+		if (rc == 0 && !do_sub && insert) {
+			// Adjust other cursors pointing to mp
+			MDB_cursor *m2, *m3;
+			MDB_dbi dbi = mc->mc_dbi;
+			unsigned i = mc->mc_top;
+			MDB_page *mp = mc->mc_pg[i];
+
+			for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (mc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3 == mc || m3->mc_snum < mc->mc_snum) continue;
+				if (m3->mc_pg[i] == mp && m3->mc_ki[i] >= mc->mc_ki[i]) {
+					m3->mc_ki[i]++;
+				}
+			}
+		}
+	}
+
+	if (rc != MDB_SUCCESS)
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	else {
+		// Now store the actual data in the child DB. Note that we're
+		// storing the user data in the keys field, so there are strict
+		// size limits on dupdata. The actual data fields of the child
+		// DB are all zero size.
+		if (do_sub) {
+			int xflags;
+put_sub:
+			xdata.mv_size = 0;
+			xdata.mv_data = "";
+			leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+			if (flags & MDB_CURRENT) {
+				xflags = MDB_CURRENT|MDB_NOSPILL;
+			} else {
+				mdb_xcursor_init1(mc, leaf);
+				xflags = (flags & MDB_NODUPDATA) ?
+					MDB_NOOVERWRITE|MDB_NOSPILL : MDB_NOSPILL;
+			}
+			// converted, write the original data first
+			if (dkey.mv_size) {
+				rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, &dkey, &xdata, xflags);
+				if (rc)
+					return rc;
+				{
+					// Adjust other cursors pointing to mp
+					MDB_cursor *m2;
+					unsigned i = mc->mc_top;
+					MDB_page *mp = mc->mc_pg[i];
+
+					for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+						if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
+						if (!(m2->mc_flags & C_INITIALIZED)) continue;
+						if (m2->mc_pg[i] == mp && m2->mc_ki[i] == mc->mc_ki[i]) {
+							mdb_xcursor_init1(m2, leaf);
+						}
+					}
+				}
+				// we've done our job
+				dkey.mv_size = 0;
+			}
+			if (flags & MDB_APPENDDUP)
+				xflags |= MDB_APPEND;
+			rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, data, &xdata, xflags);
+			if (flags & F_SUBDATA) {
+				void *db = NODEDATA(leaf);
+				memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
+			}
+		}
+		// sub-writes might have failed so check rc again.
+		// Don't increment count if we just replaced an existing item.
+		if (!rc && !(flags & MDB_CURRENT))
+			mc->mc_db->md_entries++;
+		if (flags & MDB_MULTIPLE) {
+			if (!rc) {
+next_mult:
+				mcount++;
+				// let caller know how many succeeded, if any
+				data[1].mv_size = mcount;
+				if (mcount < dcount) {
+					data[0].mv_data = (char *)data[0].mv_data + data[0].mv_size;
+					goto more;
+				}
+			}
+		}
+	}
+done:
+	// If we succeeded and the key didn't exist before, make sure
+	// the cursor is marked valid.
+	if (!rc && insert)
+		mc->mc_flags |= C_INITIALIZED;
+	return rc;
+	*/
+	return nil
+}
+
+func (c *cursor) Del(flags int) error {
+	/*
+	MDB_node	*leaf;
+	MDB_page	*mp;
+	int rc;
+
+	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_ERROR))
+		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	if (!(mc->mc_flags & C_INITIALIZED))
+		return EINVAL;
+
+	if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top]))
+		return MDB_NOTFOUND;
+
+	if (!(flags & MDB_NOSPILL) && (rc = mdb_page_spill(mc, NULL, NULL)))
+		return rc;
+
+	rc = mdb_cursor_touch(mc);
+	if (rc)
+		return rc;
+
+	mp = mc->mc_pg[mc->mc_top];
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (!IS_LEAF2(mp) && F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		if (!(flags & MDB_NODUPDATA)) {
+			if (!F_ISSET(leaf->mn_flags, F_SUBDATA)) {
+				mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+			}
+			rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, MDB_NOSPILL);
+			// If sub-DB still has entries, we're done
+			if (mc->mc_xcursor->mx_db.md_entries) {
+				if (leaf->mn_flags & F_SUBDATA) {
+					// update subDB info
+					void *db = NODEDATA(leaf);
+					memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
+				} else {
+					MDB_cursor *m2;
+					// shrink fake page
+					mdb_node_shrink(mp, mc->mc_ki[mc->mc_top]);
+					leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+					mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+					// fix other sub-DB cursors pointed at this fake page
+					for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+						if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
+						if (m2->mc_pg[mc->mc_top] == mp &&
+							m2->mc_ki[mc->mc_top] == mc->mc_ki[mc->mc_top])
+							m2->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+					}
+				}
+				mc->mc_db->md_entries--;
+				mc->mc_flags |= C_DEL;
+				return rc;
+			}
+			// otherwise fall thru and delete the sub-DB
+		}
+
+		if (leaf->mn_flags & F_SUBDATA) {
+			// add all the child DB's pages to the free list
+			rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
+			if (rc == MDB_SUCCESS) {
+				mc->mc_db->md_entries -=
+					mc->mc_xcursor->mx_db.md_entries;
+			}
+		}
+	}
+
+	return mdb_cursor_del0(mc, leaf);
+	*/
+	return nil
+}
+
+// Allocate and initialize new pages for a database.
+// @param[in] mc a cursor on the database being added to.
+// @param[in] flags flags defining what type of page is being allocated.
+// @param[in] num the number of pages to allocate. This is usually 1,
+// unless allocating overflow pages for a large record.
+// @param[out] mp Address of a page, or NULL on failure.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) newPage(flags int, num int) ([]*page, error) {
+	/*
+	MDB_page	*np;
+	int rc;
+
+	if ((rc = mdb_page_alloc(mc, num, &np)))
+		return rc;
+	DPRINTF(("allocated new mpage %"Z"u, page size %u",
+	    np->mp_pgno, mc->mc_txn->mt_env->me_psize));
+	np->mp_flags = flags | P_DIRTY;
+	np->mp_lower = PAGEHDRSZ;
+	np->mp_upper = mc->mc_txn->mt_env->me_psize;
+
+	if (IS_BRANCH(np))
+		mc->mc_db->md_branch_pages++;
+	else if (IS_LEAF(np))
+		mc->mc_db->md_leaf_pages++;
+	else if (IS_OVERFLOW(np)) {
+		mc->mc_db->md_overflow_pages += num;
+		np->mp_pages = num;
+	}
+	*mp = np;
+
+	return 0;
+	*/
+	return nil, nil
+}
+
+// Add a node to the page pointed to by the cursor.
+// @param[in] mc The cursor for this operation.
+// @param[in] indx The index on the page where the new node should be added.
+// @param[in] key The key for the new node.
+// @param[in] data The data for the new node, if any.
+// @param[in] pgno The page number, if adding a branch node.
+// @param[in] flags Flags for the node.
+// @return 0 on success, non-zero on failure. Possible errors are:
+// <ul>
+//	<li>ENOMEM - failed to allocate overflow pages for the node.
+//	<li>MDB_PAGE_FULL - there is insufficient room in the page. This error
+//	should never happen since all callers already calculate the
+//	page's free space before calling this function.
+// </ul>
+func (c *cursor) addNode(index int, key []byte, data []byte, pgno int, flags int) error {
+	/*
+	unsigned int	 i;
+	size_t		 node_size = NODESIZE;
+	ssize_t		 room;
+	indx_t		 ofs;
+	MDB_node	*node;
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	MDB_page	*ofp = NULL;		// overflow page
+	DKBUF;
+
+	mdb_cassert(mc, mp->mp_upper >= mp->mp_lower);
+
+	DPRINTF(("add to %s %spage %"Z"u index %i, data size %"Z"u key size %"Z"u [%s]",
+	    IS_LEAF(mp) ? "leaf" : "branch",
+		IS_SUBP(mp) ? "sub-" : "",
+		mdb_dbg_pgno(mp), indx, data ? data->mv_size : 0,
+		key ? key->mv_size : 0, key ? DKEY(key) : "null"));
+
+	if (IS_LEAF2(mp)) {
+		// Move higher keys up one slot.
+		int ksize = mc->mc_db->md_pad, dif;
+		char *ptr = LEAF2KEY(mp, indx, ksize);
+		dif = NUMKEYS(mp) - indx;
+		if (dif > 0)
+			memmove(ptr+ksize, ptr, dif*ksize);
+		// insert new key
+		memcpy(ptr, key->mv_data, ksize);
+
+		// Just using these for counting
+		mp->mp_lower += sizeof(indx_t);
+		mp->mp_upper -= ksize - sizeof(indx_t);
+		return MDB_SUCCESS;
+	}
+
+	room = (ssize_t)SIZELEFT(mp) - (ssize_t)sizeof(indx_t);
+	if (key != NULL)
+		node_size += key->mv_size;
+	if (IS_LEAF(mp)) {
+		mdb_cassert(mc, data);
+		if (F_ISSET(flags, F_BIGDATA)) {
+			// Data already on overflow page.
+			node_size += sizeof(pgno_t);
+		} else if (node_size + data->mv_size > mc->mc_txn->mt_env->me_nodemax) {
+			int ovpages = OVPAGES(data->mv_size, mc->mc_txn->mt_env->me_psize);
+			int rc;
+			// Put data on overflow page.
+			DPRINTF(("data size is %"Z"u, node would be %"Z"u, put data on overflow page",
+			    data->mv_size, node_size+data->mv_size));
+			node_size = EVEN(node_size + sizeof(pgno_t));
+			if ((ssize_t)node_size > room)
+				goto full;
+			if ((rc = mdb_page_new(mc, P_OVERFLOW, ovpages, &ofp)))
+				return rc;
+			DPRINTF(("allocated overflow page %"Z"u", ofp->mp_pgno));
+			flags |= F_BIGDATA;
+			goto update;
+		} else {
+			node_size += data->mv_size;
+		}
+	}
+	node_size = EVEN(node_size);
+	if ((ssize_t)node_size > room)
+		goto full;
+
+update:
+	// Move higher pointers up one slot.
+	for (i = NUMKEYS(mp); i > indx; i--)
+		mp->mp_ptrs[i] = mp->mp_ptrs[i - 1];
+
+	// Adjust free space offsets.
+	ofs = mp->mp_upper - node_size;
+	mdb_cassert(mc, ofs >= mp->mp_lower + sizeof(indx_t));
+	mp->mp_ptrs[indx] = ofs;
+	mp->mp_upper = ofs;
+	mp->mp_lower += sizeof(indx_t);
+
+	// Write the node data.
+	node = NODEPTR(mp, indx);
+	node->mn_ksize = (key == NULL) ? 0 : key->mv_size;
+	node->mn_flags = flags;
+	if (IS_LEAF(mp))
+		SETDSZ(node,data->mv_size);
+	else
+		SETPGNO(node,pgno);
+
+	if (key)
+		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
+
+	if (IS_LEAF(mp)) {
+		mdb_cassert(mc, key);
+		if (ofp == NULL) {
+			if (F_ISSET(flags, F_BIGDATA))
+				memcpy(node->mn_data + key->mv_size, data->mv_data,
+				    sizeof(pgno_t));
+			else if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = node->mn_data + key->mv_size;
+			else
+				memcpy(node->mn_data + key->mv_size, data->mv_data,
+				    data->mv_size);
+		} else {
+			memcpy(node->mn_data + key->mv_size, &ofp->mp_pgno,
+			    sizeof(pgno_t));
+			if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = METADATA(ofp);
+			else
+				memcpy(METADATA(ofp), data->mv_data, data->mv_size);
+		}
+	}
+
+	return MDB_SUCCESS;
+
+full:
+	DPRINTF(("not enough room in page %"Z"u, got %u ptrs",
+		mdb_dbg_pgno(mp), NUMKEYS(mp)));
+	DPRINTF(("upper-lower = %u - %u = %"Z"d", mp->mp_upper,mp->mp_lower,room));
+	DPRINTF(("node size = %"Z"u", node_size));
+	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return MDB_PAGE_FULL;
+	*/
+
+	return nil
+}
+
+// Delete the specified node from a page.
+// @param[in] mp The page to operate on.
+// @param[in] indx The index of the node to delete.
+// @param[in] ksize The size of a node. Only used if the page is
+// part of a #MDB_DUPFIXED database.
+func (c *cursor) deleteNode(ksize int) {
+	/*
+	MDB_page *mp = mc->mc_pg[mc->mc_top];
+	indx_t	indx = mc->mc_ki[mc->mc_top];
+	unsigned int	 sz;
+	indx_t		 i, j, numkeys, ptr;
+	MDB_node	*node;
+	char		*base;
+
+	DPRINTF(("delete node %u on %s page %"Z"u", indx,
+	    IS_LEAF(mp) ? "leaf" : "branch", mdb_dbg_pgno(mp)));
+	numkeys = NUMKEYS(mp);
+	mdb_cassert(mc, indx < numkeys);
+
+	if (IS_LEAF2(mp)) {
+		int x = numkeys - 1 - indx;
+		base = LEAF2KEY(mp, indx, ksize);
+		if (x)
+			memmove(base, base + ksize, x * ksize);
+		mp->mp_lower -= sizeof(indx_t);
+		mp->mp_upper += ksize - sizeof(indx_t);
+		return;
+	}
+
+	node = NODEPTR(mp, indx);
+	sz = NODESIZE + node->mn_ksize;
+	if (IS_LEAF(mp)) {
+		if (F_ISSET(node->mn_flags, F_BIGDATA))
+			sz += sizeof(pgno_t);
+		else
+			sz += NODEDSZ(node);
+	}
+	sz = EVEN(sz);
+
+	ptr = mp->mp_ptrs[indx];
+	for (i = j = 0; i < numkeys; i++) {
+		if (i != indx) {
+			mp->mp_ptrs[j] = mp->mp_ptrs[i];
+			if (mp->mp_ptrs[i] < ptr)
+				mp->mp_ptrs[j] += sz;
+			j++;
+		}
+	}
+
+	base = (char *)mp + mp->mp_upper;
+	memmove(base + sz, base, ptr - mp->mp_upper);
+
+	mp->mp_lower -= sizeof(indx_t);
+	mp->mp_upper += sz;
+*/
+}
+
+// Initial setup of a sorted-dups cursor.
+// Sorted duplicates are implemented as a sub-database for the given key.
+// The duplicate data items are actually keys of the sub-database.
+// Operations on the duplicate data items are performed using a sub-cursor
+// initialized when the sub-database is first accessed. This function does
+// the preliminary setup of the sub-cursor, filling in the fields that
+// depend only on the parent DB.
+// @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
+func (c *cursor) xcursor_init0() {
+	/*
+	MDB_xcursor *mx = mc->mc_xcursor;
+
+	mx->mx_cursor.mc_xcursor = NULL;
+	mx->mx_cursor.mc_txn = mc->mc_txn;
+	mx->mx_cursor.mc_db = &mx->mx_db;
+	mx->mx_cursor.mc_dbx = &mx->mx_dbx;
+	mx->mx_cursor.mc_dbi = mc->mc_dbi;
+	mx->mx_cursor.mc_dbflag = &mx->mx_dbflag;
+	mx->mx_cursor.mc_snum = 0;
+	mx->mx_cursor.mc_top = 0;
+	mx->mx_cursor.mc_flags = C_SUB;
+	mx->mx_dbx.md_name.mv_size = 0;
+	mx->mx_dbx.md_name.mv_data = NULL;
+	mx->mx_dbx.md_cmp = mc->mc_dbx->md_dcmp;
+	mx->mx_dbx.md_dcmp = NULL;
+	mx->mx_dbx.md_rel = mc->mc_dbx->md_rel;
+	*/
+}
+
+// Final setup of a sorted-dups cursor.
+//	Sets up the fields that depend on the data from the main cursor.
+// @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
+// @param[in] node The data containing the #MDB_db record for the
+// sorted-dup database.
+func (c *cursor) xcursor_init1(n *node) {
+	/*
+	MDB_xcursor *mx = mc->mc_xcursor;
+
+	if (node->mn_flags & F_SUBDATA) {
+		memcpy(&mx->mx_db, NODEDATA(node), sizeof(MDB_db));
+		mx->mx_cursor.mc_pg[0] = 0;
+		mx->mx_cursor.mc_snum = 0;
+		mx->mx_cursor.mc_top = 0;
+		mx->mx_cursor.mc_flags = C_SUB;
+	} else {
+		MDB_page *fp = NODEDATA(node);
+		mx->mx_db.md_pad = mc->mc_pg[mc->mc_top]->mp_pad;
+		mx->mx_db.md_flags = 0;
+		mx->mx_db.md_depth = 1;
+		mx->mx_db.md_branch_pages = 0;
+		mx->mx_db.md_leaf_pages = 1;
+		mx->mx_db.md_overflow_pages = 0;
+		mx->mx_db.md_entries = NUMKEYS(fp);
+		COPY_PGNO(mx->mx_db.md_root, fp->mp_pgno);
+		mx->mx_cursor.mc_snum = 1;
+		mx->mx_cursor.mc_top = 0;
+		mx->mx_cursor.mc_flags = C_INITIALIZED|C_SUB;
+		mx->mx_cursor.mc_pg[0] = fp;
+		mx->mx_cursor.mc_ki[0] = 0;
+		if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+			mx->mx_db.md_flags = MDB_DUPFIXED;
+			mx->mx_db.md_pad = fp->mp_pad;
+			if (mc->mc_db->md_flags & MDB_INTEGERDUP)
+				mx->mx_db.md_flags |= MDB_INTEGERKEY;
+		}
+	}
+	DPRINTF(("Sub-db -%u root page %"Z"u", mx->mx_cursor.mc_dbi,
+		mx->mx_db.md_root));
+	mx->mx_dbflag = DB_VALID|DB_DIRTY; // DB_DIRTY guides mdb_cursor_touch
+#if UINT_MAX < SIZE_MAX
+	if (mx->mx_dbx.md_cmp == mdb_cmp_int && mx->mx_db.md_pad == sizeof(size_t))
+#ifdef MISALIGNED_OK
+		mx->mx_dbx.md_cmp = mdb_cmp_long;
+#else
+		mx->mx_dbx.md_cmp = mdb_cmp_cint;
+#endif
+#endif
+	*/
+}
+
+// Initialize a cursor for a given transaction and database.
+func (c *cursor) init(t *transaction, bucket *bucket, mx *xcursor) {
+	/*
+	mc->mc_next = NULL;
+	mc->mc_backup = NULL;
+	mc->mc_dbi = dbi;
+	mc->mc_txn = txn;
+	mc->mc_db = &txn->mt_dbs[dbi];
+	mc->mc_dbx = &txn->mt_dbxs[dbi];
+	mc->mc_dbflag = &txn->mt_dbflags[dbi];
+	mc->mc_snum = 0;
+	mc->mc_top = 0;
+	mc->mc_pg[0] = 0;
+	mc->mc_flags = 0;
+	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT) {
+		mdb_tassert(txn, mx != NULL);
+		mc->mc_xcursor = mx;
+		mdb_xcursor_init0(mc);
+	} else {
+		mc->mc_xcursor = NULL;
+	}
+	if (*mc->mc_dbflag & DB_STALE) {
+		mdb_page_search(mc, NULL, MDB_PS_ROOTONLY);
+	}
+	*/
+}
+
+// Return the count of duplicate data items for the current key.
+func (c *cursor) count() (int, error) {
+	/*
+	MDB_node	*leaf;
+
+	if (mc == NULL || countp == NULL)
+		return EINVAL;
+
+	if (mc->mc_xcursor == NULL)
+		return MDB_INCOMPATIBLE;
+
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+	if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		*countp = 1;
+	} else {
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
+			return EINVAL;
+
+		*countp = mc->mc_xcursor->mx_db.md_entries;
+	}
+	return MDB_SUCCESS;
+	*/
+	return 0, nil
+}
+
+func (c *cursor) Close() {
+	/*
+	if (mc && !mc->mc_backup) {
+		// remove from txn, if tracked
+		if ((mc->mc_flags & C_UNTRACK) && mc->mc_txn->mt_cursors) {
+			MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi];
+			while (*prev && *prev != mc) prev = &(*prev)->mc_next;
+			if (*prev == mc)
+				*prev = mc->mc_next;
+		}
+		free(mc);
+	}
+	*/
+}
+
+func (c *cursor) Transaction() Transaction {
+	/*
+	if (!mc) return NULL;
+	return mc->mc_txn;
+	*/
+	return nil
+}
+
+func (c *cursor) Bucket() Bucket {
+	return c.bucket
+}
+
+// Replace the key for a branch node with a new key.
+// @param[in] mc Cursor pointing to the node to operate on.
+// @param[in] key The new key to use.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) updateKey(key []byte) error {
+	/*
+	MDB_page		*mp;
+	MDB_node		*node;
+	char			*base;
+	size_t			 len;
+	int				 delta, ksize, oksize;
+	indx_t			 ptr, i, numkeys, indx;
+	DKBUF;
+
+	indx = mc->mc_ki[mc->mc_top];
+	mp = mc->mc_pg[mc->mc_top];
+	node = NODEPTR(mp, indx);
+	ptr = mp->mp_ptrs[indx];
+#if MDB_DEBUG
+	{
+		MDB_val	k2;
+		char kbuf2[DKBUF_MAXKEYSIZE*2+1];
+		k2.mv_data = NODEKEY(node);
+		k2.mv_size = node->mn_ksize;
+		DPRINTF(("update key %u (ofs %u) [%s] to [%s] on page %"Z"u",
+			indx, ptr,
+			mdb_dkey(&k2, kbuf2),
+			DKEY(key),
+			mp->mp_pgno));
+	}
+#endif
+
+	// Sizes must be 2-byte aligned.
+	ksize = EVEN(key->mv_size);
+	oksize = EVEN(node->mn_ksize);
+	delta = ksize - oksize;
+
+	// Shift node contents if EVEN(key length) changed.
+	if (delta) {
+		if (delta > 0 && SIZELEFT(mp) < delta) {
+			pgno_t pgno;
+			// not enough space left, do a delete and split
+			DPRINTF(("Not enough room, delta = %d, splitting...", delta));
+			pgno = NODEPGNO(node);
+			mdb_node_del(mc, 0);
+			return mdb_page_split(mc, key, NULL, pgno, MDB_SPLIT_REPLACE);
+		}
+
+		numkeys = NUMKEYS(mp);
+		for (i = 0; i < numkeys; i++) {
+			if (mp->mp_ptrs[i] <= ptr)
+				mp->mp_ptrs[i] -= delta;
+		}
+
+		base = (char *)mp + mp->mp_upper;
+		len = ptr - mp->mp_upper + NODESIZE;
+		memmove(base - delta, base, len);
+		mp->mp_upper -= delta;
+
+		node = NODEPTR(mp, indx);
+	}
+
+	// But even if no shift was needed, update ksize
+	if (node->mn_ksize != key->mv_size)
+		node->mn_ksize = key->mv_size;
+
+	if (key->mv_size)
+		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Move a node from csrc to cdst.
+func (c *cursor) moveNodeTo(dst *cursor) error {
+	/*
+	MDB_node		*srcnode;
+	MDB_val		 key, data;
+	pgno_t	srcpg;
+	MDB_cursor mn;
+	int			 rc;
+	unsigned short flags;
+
+	DKBUF;
+
+	// Mark src and dst as dirty.
+	if ((rc = mdb_page_touch(csrc)) ||
+	    (rc = mdb_page_touch(cdst)))
+		return rc;
+
+	if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+		key.mv_size = csrc->mc_db->md_pad;
+		key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top], key.mv_size);
+		data.mv_size = 0;
+		data.mv_data = NULL;
+		srcpg = 0;
+		flags = 0;
+	} else {
+		srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top]);
+		mdb_cassert(csrc, !((size_t)srcnode & 1));
+		srcpg = NODEPGNO(srcnode);
+		flags = srcnode->mn_flags;
+		if (csrc->mc_ki[csrc->mc_top] == 0 && IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
+			unsigned int snum = csrc->mc_snum;
+			MDB_node *s2;
+			// must find the lowest key below src
+			mdb_page_search_lowest(csrc);
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_size = csrc->mc_db->md_pad;
+				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
+			} else {
+				s2 = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
+				key.mv_size = NODEKSZ(s2);
+				key.mv_data = NODEKEY(s2);
+			}
+			csrc->mc_snum = snum--;
+			csrc->mc_top = snum;
+		} else {
+			key.mv_size = NODEKSZ(srcnode);
+			key.mv_data = NODEKEY(srcnode);
+		}
+		data.mv_size = NODEDSZ(srcnode);
+		data.mv_data = NODEDATA(srcnode);
+	}
+	if (IS_BRANCH(cdst->mc_pg[cdst->mc_top]) && cdst->mc_ki[cdst->mc_top] == 0) {
+		unsigned int snum = cdst->mc_snum;
+		MDB_node *s2;
+		MDB_val bkey;
+		// must find the lowest key below dst
+		mdb_page_search_lowest(cdst);
+		if (IS_LEAF2(cdst->mc_pg[cdst->mc_top])) {
+			bkey.mv_size = cdst->mc_db->md_pad;
+			bkey.mv_data = LEAF2KEY(cdst->mc_pg[cdst->mc_top], 0, bkey.mv_size);
+		} else {
+			s2 = NODEPTR(cdst->mc_pg[cdst->mc_top], 0);
+			bkey.mv_size = NODEKSZ(s2);
+			bkey.mv_data = NODEKEY(s2);
+		}
+		cdst->mc_snum = snum--;
+		cdst->mc_top = snum;
+		mdb_cursor_copy(cdst, &mn);
+		mn.mc_ki[snum] = 0;
+		rc = mdb_update_key(&mn, &bkey);
+		if (rc)
+			return rc;
+	}
+
+	DPRINTF(("moving %s node %u [%s] on page %"Z"u to node %u on page %"Z"u",
+	    IS_LEAF(csrc->mc_pg[csrc->mc_top]) ? "leaf" : "branch",
+	    csrc->mc_ki[csrc->mc_top],
+		DKEY(&key),
+	    csrc->mc_pg[csrc->mc_top]->mp_pgno,
+	    cdst->mc_ki[cdst->mc_top], cdst->mc_pg[cdst->mc_top]->mp_pgno));
+
+	// Add the node to the destination page.
+	rc = mdb_node_add(cdst, cdst->mc_ki[cdst->mc_top], &key, &data, srcpg, flags);
+	if (rc != MDB_SUCCESS)
+		return rc;
+
+	// Delete the node from the source page.
+	mdb_node_del(csrc, key.mv_size);
+
+	{
+		// Adjust other cursors pointing to mp
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		MDB_page *mp = csrc->mc_pg[csrc->mc_top];
+
+		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (csrc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3 == csrc) continue;
+			if (m3->mc_pg[csrc->mc_top] == mp && m3->mc_ki[csrc->mc_top] ==
+				csrc->mc_ki[csrc->mc_top]) {
+				m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+				m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+			}
+		}
+	}
+
+	// Update the parent separators.
+	if (csrc->mc_ki[csrc->mc_top] == 0) {
+		if (csrc->mc_ki[csrc->mc_top-1] != 0) {
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
+			} else {
+				srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
+				key.mv_size = NODEKSZ(srcnode);
+				key.mv_data = NODEKEY(srcnode);
+			}
+			DPRINTF(("update separator for source page %"Z"u to [%s]",
+				csrc->mc_pg[csrc->mc_top]->mp_pgno, DKEY(&key)));
+			mdb_cursor_copy(csrc, &mn);
+			mn.mc_snum--;
+			mn.mc_top--;
+			if ((rc = mdb_update_key(&mn, &key)) != MDB_SUCCESS)
+				return rc;
+		}
+		if (IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
+			MDB_val	 nullkey;
+			indx_t	ix = csrc->mc_ki[csrc->mc_top];
+			nullkey.mv_size = 0;
+			csrc->mc_ki[csrc->mc_top] = 0;
+			rc = mdb_update_key(csrc, &nullkey);
+			csrc->mc_ki[csrc->mc_top] = ix;
+			mdb_cassert(csrc, rc == MDB_SUCCESS);
+		}
+	}
+
+	if (cdst->mc_ki[cdst->mc_top] == 0) {
+		if (cdst->mc_ki[cdst->mc_top-1] != 0) {
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_data = LEAF2KEY(cdst->mc_pg[cdst->mc_top], 0, key.mv_size);
+			} else {
+				srcnode = NODEPTR(cdst->mc_pg[cdst->mc_top], 0);
+				key.mv_size = NODEKSZ(srcnode);
+				key.mv_data = NODEKEY(srcnode);
+			}
+			DPRINTF(("update separator for destination page %"Z"u to [%s]",
+				cdst->mc_pg[cdst->mc_top]->mp_pgno, DKEY(&key)));
+			mdb_cursor_copy(cdst, &mn);
+			mn.mc_snum--;
+			mn.mc_top--;
+			if ((rc = mdb_update_key(&mn, &key)) != MDB_SUCCESS)
+				return rc;
+		}
+		if (IS_BRANCH(cdst->mc_pg[cdst->mc_top])) {
+			MDB_val	 nullkey;
+			indx_t	ix = cdst->mc_ki[cdst->mc_top];
+			nullkey.mv_size = 0;
+			cdst->mc_ki[cdst->mc_top] = 0;
+			rc = mdb_update_key(cdst, &nullkey);
+			cdst->mc_ki[cdst->mc_top] = ix;
+			mdb_cassert(csrc, rc == MDB_SUCCESS);
+		}
+	}
+
+	return MDB_SUCCESS;
+	*/
+
+	return nil
+}
+
+// Merge one page into another.
+//  The nodes from the page pointed to by \b csrc will
+//	be copied to the page pointed to by \b cdst and then
+//	the \b csrc page will be freed.
+// @param[in] csrc Cursor pointing to the source page.
+// @param[in] cdst Cursor pointing to the destination page.
+func (c *cursor) mergePage(dst *cursor) error {
+	/*
+	int			 rc;
+	indx_t			 i, j;
+	MDB_node		*srcnode;
+	MDB_val		 key, data;
+	unsigned	nkeys;
+
+	DPRINTF(("merging page %"Z"u into %"Z"u", csrc->mc_pg[csrc->mc_top]->mp_pgno,
+		cdst->mc_pg[cdst->mc_top]->mp_pgno));
+
+	mdb_cassert(csrc, csrc->mc_snum > 1);	// can't merge root page
+	mdb_cassert(csrc, cdst->mc_snum > 1);
+
+	// Mark dst as dirty.
+	if ((rc = mdb_page_touch(cdst)))
+		return rc;
+
+	// Move all nodes from src to dst.
+	j = nkeys = NUMKEYS(cdst->mc_pg[cdst->mc_top]);
+	if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+		key.mv_size = csrc->mc_db->md_pad;
+		key.mv_data = METADATA(csrc->mc_pg[csrc->mc_top]);
+		for (i = 0; i < NUMKEYS(csrc->mc_pg[csrc->mc_top]); i++, j++) {
+			rc = mdb_node_add(cdst, j, &key, NULL, 0, 0);
+			if (rc != MDB_SUCCESS)
+				return rc;
+			key.mv_data = (char *)key.mv_data + key.mv_size;
+		}
+	} else {
+		for (i = 0; i < NUMKEYS(csrc->mc_pg[csrc->mc_top]); i++, j++) {
+			srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], i);
+			if (i == 0 && IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
+				unsigned int snum = csrc->mc_snum;
+				MDB_node *s2;
+				// must find the lowest key below src
+				mdb_page_search_lowest(csrc);
+				if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+					key.mv_size = csrc->mc_db->md_pad;
+					key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
+				} else {
+					s2 = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
+					key.mv_size = NODEKSZ(s2);
+					key.mv_data = NODEKEY(s2);
+				}
+				csrc->mc_snum = snum--;
+				csrc->mc_top = snum;
+			} else {
+				key.mv_size = srcnode->mn_ksize;
+				key.mv_data = NODEKEY(srcnode);
+			}
+
+			data.mv_size = NODEDSZ(srcnode);
+			data.mv_data = NODEDATA(srcnode);
+			rc = mdb_node_add(cdst, j, &key, &data, NODEPGNO(srcnode), srcnode->mn_flags);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	DPRINTF(("dst page %"Z"u now has %u keys (%.1f%% filled)",
+	    cdst->mc_pg[cdst->mc_top]->mp_pgno, NUMKEYS(cdst->mc_pg[cdst->mc_top]),
+		(float)PAGEFILL(cdst->mc_txn->mt_env, cdst->mc_pg[cdst->mc_top]) / 10));
+
+	// Unlink the src page from parent and add to free list.
+	csrc->mc_top--;
+	mdb_node_del(csrc, 0);
+	if (csrc->mc_ki[csrc->mc_top] == 0) {
+		key.mv_size = 0;
+		rc = mdb_update_key(csrc, &key);
+		if (rc) {
+			csrc->mc_top++;
+			return rc;
+		}
+	}
+	csrc->mc_top++;
+
+	rc = mdb_midl_append(&csrc->mc_txn->mt_free_pgs,
+		csrc->mc_pg[csrc->mc_top]->mp_pgno);
+	if (rc)
+		return rc;
+	if (IS_LEAF(csrc->mc_pg[csrc->mc_top]))
+		csrc->mc_db->md_leaf_pages--;
+	else
+		csrc->mc_db->md_branch_pages--;
+	{
+		// Adjust other cursors pointing to mp 
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		MDB_page *mp = cdst->mc_pg[cdst->mc_top];
+
+		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (csrc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3 == csrc) continue;
+			if (m3->mc_snum < csrc->mc_snum) continue;
+			if (m3->mc_pg[csrc->mc_top] == csrc->mc_pg[csrc->mc_top]) {
+				m3->mc_pg[csrc->mc_top] = mp;
+				m3->mc_ki[csrc->mc_top] += nkeys;
+			}
+		}
+	}
+	mdb_cursor_pop(csrc);
+
+	return mdb_rebalance(csrc);
+	*/
+
+	return nil
+}
+
+// Copy the contents of a cursor.
+// @param[in] csrc The cursor to copy from.
+// @param[out] cdst The cursor to copy to.
+func (c *cursor) copyTo(dst *cursor) {
+	/*
+	unsigned int i;
+
+	cdst->mc_txn = csrc->mc_txn;
+	cdst->mc_dbi = csrc->mc_dbi;
+	cdst->mc_db  = csrc->mc_db;
+	cdst->mc_dbx = csrc->mc_dbx;
+	cdst->mc_snum = csrc->mc_snum;
+	cdst->mc_top = csrc->mc_top;
+	cdst->mc_flags = csrc->mc_flags;
+
+	for (i=0; i<csrc->mc_snum; i++) {
+		cdst->mc_pg[i] = csrc->mc_pg[i];
+		cdst->mc_ki[i] = csrc->mc_ki[i];
+	}
+	*/
+}
+
+// Rebalance the tree after a delete operation.
+// @param[in] mc Cursor pointing to the page where rebalancing
+// should begin.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) rebalance() error {
+	/*
+	MDB_node	*node;
+	int rc;
+	unsigned int ptop, minkeys;
+	MDB_cursor	mn;
+
+	minkeys = 1 + (IS_BRANCH(mc->mc_pg[mc->mc_top]));
+	DPRINTF(("rebalancing %s page %"Z"u (has %u keys, %.1f%% full)",
+	    IS_LEAF(mc->mc_pg[mc->mc_top]) ? "leaf" : "branch",
+	    mdb_dbg_pgno(mc->mc_pg[mc->mc_top]), NUMKEYS(mc->mc_pg[mc->mc_top]),
+		(float)PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) / 10));
+
+	if (PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) >= FILL_THRESHOLD &&
+		NUMKEYS(mc->mc_pg[mc->mc_top]) >= minkeys) {
+		DPRINTF(("no need to rebalance page %"Z"u, above fill threshold",
+		    mdb_dbg_pgno(mc->mc_pg[mc->mc_top])));
+		return MDB_SUCCESS;
+	}
+
+	if (mc->mc_snum < 2) {
+		MDB_page *mp = mc->mc_pg[0];
+		if (IS_SUBP(mp)) {
+			DPUTS("Can't rebalance a subpage, ignoring");
+			return MDB_SUCCESS;
+		}
+		if (NUMKEYS(mp) == 0) {
+			DPUTS("tree is completely empty");
+			mc->mc_db->md_root = P_INVALID;
+			mc->mc_db->md_depth = 0;
+			mc->mc_db->md_leaf_pages = 0;
+			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
+			if (rc)
+				return rc;
+			// Adjust cursors pointing to mp
+			mc->mc_snum = 0;
+			mc->mc_top = 0;
+			mc->mc_flags &= ~C_INITIALIZED;
+			{
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (m3->mc_snum < mc->mc_snum) continue;
+					if (m3->mc_pg[0] == mp) {
+						m3->mc_snum = 0;
+						m3->mc_top = 0;
+						m3->mc_flags &= ~C_INITIALIZED;
+					}
+				}
+			}
+		} else if (IS_BRANCH(mp) && NUMKEYS(mp) == 1) {
+			DPUTS("collapsing root page!");
+			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
+			if (rc)
+				return rc;
+			mc->mc_db->md_root = NODEPGNO(NODEPTR(mp, 0));
+			rc = mdb_page_get(mc->mc_txn,mc->mc_db->md_root,&mc->mc_pg[0],NULL);
+			if (rc)
+				return rc;
+			mc->mc_db->md_depth--;
+			mc->mc_db->md_branch_pages--;
+			mc->mc_ki[0] = mc->mc_ki[1];
+			{
+				// Adjust other cursors pointing to mp
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (m3 == mc || m3->mc_snum < mc->mc_snum) continue;
+					if (m3->mc_pg[0] == mp) {
+						int i;
+						m3->mc_snum--;
+						m3->mc_top--;
+						for (i=0; i<m3->mc_snum; i++) {
+							m3->mc_pg[i] = m3->mc_pg[i+1];
+							m3->mc_ki[i] = m3->mc_ki[i+1];
+						}
+					}
+				}
+			}
+		} else
+			DPUTS("root page doesn't need rebalancing");
+		return MDB_SUCCESS;
+	}
+
+	// The parent (branch page) must have at least 2 pointers,
+	// otherwise the tree is invalid.
+	ptop = mc->mc_top-1;
+	mdb_cassert(mc, NUMKEYS(mc->mc_pg[ptop]) > 1);
+
+	// Leaf page fill factor is below the threshold.
+	// Try to move keys from left or right neighbor, or
+	// merge with a neighbor page.
+
+	// Find neighbors.
+	mdb_cursor_copy(mc, &mn);
+	mn.mc_xcursor = NULL;
+
+	if (mc->mc_ki[ptop] == 0) {
+		// We're the leftmost leaf in our parent.
+		DPUTS("reading right neighbor");
+		mn.mc_ki[ptop]++;
+		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
+		rc = mdb_page_get(mc->mc_txn,NODEPGNO(node),&mn.mc_pg[mn.mc_top],NULL);
+		if (rc)
+			return rc;
+		mn.mc_ki[mn.mc_top] = 0;
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]);
+	} else {
+		// There is at least one neighbor to the left.
+		DPUTS("reading left neighbor");
+		mn.mc_ki[ptop]--;
+		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
+		rc = mdb_page_get(mc->mc_txn,NODEPGNO(node),&mn.mc_pg[mn.mc_top],NULL);
+		if (rc)
+			return rc;
+		mn.mc_ki[mn.mc_top] = NUMKEYS(mn.mc_pg[mn.mc_top]) - 1;
+		mc->mc_ki[mc->mc_top] = 0;
+	}
+
+	DPRINTF(("found neighbor page %"Z"u (%u keys, %.1f%% full)",
+	    mn.mc_pg[mn.mc_top]->mp_pgno, NUMKEYS(mn.mc_pg[mn.mc_top]),
+		(float)PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) / 10));
+
+	// If the neighbor page is above threshold and has enough keys,
+	// move one key from it. Otherwise we should try to merge them.
+	// (A branch page must never have less than 2 keys.)
+	minkeys = 1 + (IS_BRANCH(mn.mc_pg[mn.mc_top]));
+	if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= FILL_THRESHOLD && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys)
+		return mdb_node_move(&mn, mc);
+	else {
+		if (mc->mc_ki[ptop] == 0)
+			rc = mdb_page_merge(&mn, mc);
+		else {
+			mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
+			rc = mdb_page_merge(mc, &mn);
+			mdb_cursor_copy(&mn, mc);
+		}
+		mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+	}
+	return rc;
+	*/
+	return nil
+}
+
+// Complete a delete operation started by #mdb_cursor_del().
+func (c *cursor) del0(leaf *node) error {
+	/*
+	int rc;
+	MDB_page *mp;
+	indx_t ki;
+	unsigned int nkeys;
+
+	mp = mc->mc_pg[mc->mc_top];
+	ki = mc->mc_ki[mc->mc_top];
+
+	// add overflow pages to free list
+	if (!IS_LEAF2(mp) && F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+		MDB_page *omp;
+		pgno_t pg;
+
+		memcpy(&pg, NODEDATA(leaf), sizeof(pg));
+		if ((rc = mdb_page_get(mc->mc_txn, pg, &omp, NULL)) ||
+			(rc = mdb_ovpage_free(mc, omp)))
+			return rc;
+	}
+	mdb_node_del(mc, mc->mc_db->md_pad);
+	mc->mc_db->md_entries--;
+	rc = mdb_rebalance(mc);
+	if (rc != MDB_SUCCESS)
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	else {
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = mc->mc_dbi;
+
+		mp = mc->mc_pg[mc->mc_top];
+		nkeys = NUMKEYS(mp);
+
+		// if mc points past last node in page, find next sibling
+		if (mc->mc_ki[mc->mc_top] >= nkeys)
+			mdb_cursor_sibling(mc, 1);
+
+		// Adjust other cursors pointing to mp
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+			if (! (m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+				continue;
+			if (m3 == mc || m3->mc_snum < mc->mc_snum)
+				continue;
+			if (m3->mc_pg[mc->mc_top] == mp) {
+				if (m3->mc_ki[mc->mc_top] >= ki) {
+					m3->mc_flags |= C_DEL;
+					if (m3->mc_ki[mc->mc_top] > ki)
+						m3->mc_ki[mc->mc_top]--;
+				}
+				if (m3->mc_ki[mc->mc_top] >= nkeys)
+					mdb_cursor_sibling(m3, 1);
+			}
+		}
+		mc->mc_flags |= C_DEL;
+	}
+
+	return rc;
+	*/
+	return nil
+}
+
+// Split a page and insert a new node.
+// @param[in,out] mc Cursor pointing to the page and desired insertion index.
+// The cursor will be updated to point to the actual page and index where
+// the node got inserted after the split.
+// @param[in] newkey The key for the newly inserted node.
+// @param[in] newdata The data for the newly inserted node.
+// @param[in] newpgno The page number, if the new node is a branch node.
+// @param[in] nflags The #NODE_ADD_FLAGS for the new node.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) splitPage(newKey []byte, newData []byte, newpgno int, nflags int) error {
+	/*
+	unsigned int flags;
+	int		 rc = MDB_SUCCESS, new_root = 0, did_split = 0;
+	indx_t		 newindx;
+	pgno_t		 pgno = 0;
+	int	 i, j, split_indx, nkeys, pmax;
+	MDB_env 	*env = mc->mc_txn->mt_env;
+	MDB_node	*node;
+	MDB_val	 sepkey, rkey, xdata, *rdata = &xdata;
+	MDB_page	*copy = NULL;
+	MDB_page	*mp, *rp, *pp;
+	int ptop;
+	MDB_cursor	mn;
+	DKBUF;
+
+	mp = mc->mc_pg[mc->mc_top];
+	newindx = mc->mc_ki[mc->mc_top];
+	nkeys = NUMKEYS(mp);
+
+	DPRINTF(("-----> splitting %s page %"Z"u and adding [%s] at index %i/%i",
+	    IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno,
+	    DKEY(newkey), mc->mc_ki[mc->mc_top], nkeys));
+
+	// Create a right sibling.
+	if ((rc = mdb_page_new(mc, mp->mp_flags, 1, &rp)))
+		return rc;
+	DPRINTF(("new right sibling: page %"Z"u", rp->mp_pgno));
+
+	if (mc->mc_snum < 2) {
+		if ((rc = mdb_page_new(mc, P_BRANCH, 1, &pp)))
+			return rc;
+		// shift current top to make room for new parent
+		mc->mc_pg[1] = mc->mc_pg[0];
+		mc->mc_ki[1] = mc->mc_ki[0];
+		mc->mc_pg[0] = pp;
+		mc->mc_ki[0] = 0;
+		mc->mc_db->md_root = pp->mp_pgno;
+		DPRINTF(("root split! new root = %"Z"u", pp->mp_pgno));
+		mc->mc_db->md_depth++;
+		new_root = 1;
+
+		// Add left (implicit) pointer.
+		if ((rc = mdb_node_add(mc, 0, NULL, NULL, mp->mp_pgno, 0)) != MDB_SUCCESS) {
+			// undo the pre-push
+			mc->mc_pg[0] = mc->mc_pg[1];
+			mc->mc_ki[0] = mc->mc_ki[1];
+			mc->mc_db->md_root = mp->mp_pgno;
+			mc->mc_db->md_depth--;
+			return rc;
+		}
+		mc->mc_snum = 2;
+		mc->mc_top = 1;
+		ptop = 0;
+	} else {
+		ptop = mc->mc_top-1;
+		DPRINTF(("parent branch page is %"Z"u", mc->mc_pg[ptop]->mp_pgno));
+	}
+
+	mc->mc_flags |= C_SPLITTING;
+	mdb_cursor_copy(mc, &mn);
+	mn.mc_pg[mn.mc_top] = rp;
+	mn.mc_ki[ptop] = mc->mc_ki[ptop]+1;
+
+	if (nflags & MDB_APPEND) {
+		mn.mc_ki[mn.mc_top] = 0;
+		sepkey = *newkey;
+		split_indx = newindx;
+		nkeys = 0;
+	} else {
+
+		split_indx = (nkeys+1) / 2;
+
+		if (IS_LEAF2(rp)) {
+			char *split, *ins;
+			int x;
+			unsigned int lsize, rsize, ksize;
+			// Move half of the keys to the right sibling
+			copy = NULL;
+			x = mc->mc_ki[mc->mc_top] - split_indx;
+			ksize = mc->mc_db->md_pad;
+			split = LEAF2KEY(mp, split_indx, ksize);
+			rsize = (nkeys - split_indx) * ksize;
+			lsize = (nkeys - split_indx) * sizeof(indx_t);
+			mp->mp_lower -= lsize;
+			rp->mp_lower += lsize;
+			mp->mp_upper += rsize - lsize;
+			rp->mp_upper -= rsize - lsize;
+			sepkey.mv_size = ksize;
+			if (newindx == split_indx) {
+				sepkey.mv_data = newkey->mv_data;
+			} else {
+				sepkey.mv_data = split;
+			}
+			if (x<0) {
+				ins = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], ksize);
+				memcpy(rp->mp_ptrs, split, rsize);
+				sepkey.mv_data = rp->mp_ptrs;
+				memmove(ins+ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
+				memcpy(ins, newkey->mv_data, ksize);
+				mp->mp_lower += sizeof(indx_t);
+				mp->mp_upper -= ksize - sizeof(indx_t);
+			} else {
+				if (x)
+					memcpy(rp->mp_ptrs, split, x * ksize);
+				ins = LEAF2KEY(rp, x, ksize);
+				memcpy(ins, newkey->mv_data, ksize);
+				memcpy(ins+ksize, split + x * ksize, rsize - x * ksize);
+				rp->mp_lower += sizeof(indx_t);
+				rp->mp_upper -= ksize - sizeof(indx_t);
+				mc->mc_ki[mc->mc_top] = x;
+				mc->mc_pg[mc->mc_top] = rp;
+			}
+		} else {
+			int psize, nsize, k;
+			// Maximum free space in an empty page
+			pmax = env->me_psize - PAGEHDRSZ;
+			if (IS_LEAF(mp))
+				nsize = mdb_leaf_size(env, newkey, newdata);
+			else
+				nsize = mdb_branch_size(env, newkey);
+			nsize = EVEN(nsize);
+
+			// grab a page to hold a temporary copy
+			copy = mdb_page_malloc(mc->mc_txn, 1);
+			if (copy == NULL)
+				return ENOMEM;
+			copy->mp_pgno  = mp->mp_pgno;
+			copy->mp_flags = mp->mp_flags;
+			copy->mp_lower = PAGEHDRSZ;
+			copy->mp_upper = env->me_psize;
+
+			// prepare to insert
+			for (i=0, j=0; i<nkeys; i++) {
+				if (i == newindx) {
+					copy->mp_ptrs[j++] = 0;
+				}
+				copy->mp_ptrs[j++] = mp->mp_ptrs[i];
+			}
+
+			// When items are relatively large the split point needs
+			// to be checked, because being off-by-one will make the
+			// difference between success or failure in mdb_node_add.
+			//
+			// It's also relevant if a page happens to be laid out
+			// such that one half of its nodes are all "small" and
+			// the other half of its nodes are "large." If the new
+			// item is also "large" and falls on the half with
+			// "large" nodes, it also may not fit.
+			//
+			// As a final tweak, if the new item goes on the last
+			// spot on the page (and thus, onto the new page), bias
+			// the split so the new page is emptier than the old page.
+			// This yields better packing during sequential inserts.
+			if (nkeys < 20 || nsize > pmax/16 || newindx >= nkeys) {
+				// Find split point
+				psize = 0;
+				if (newindx <= split_indx || newindx >= nkeys) {
+					i = 0; j = 1;
+					k = newindx >= nkeys ? nkeys : split_indx+2;
+				} else {
+					i = nkeys; j = -1;
+					k = split_indx-1;
+				}
+				for (; i!=k; i+=j) {
+					if (i == newindx) {
+						psize += nsize;
+						node = NULL;
+					} else {
+						node = (MDB_node *)((char *)mp + copy->mp_ptrs[i]);
+						psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
+						if (IS_LEAF(mp)) {
+							if (F_ISSET(node->mn_flags, F_BIGDATA))
+								psize += sizeof(pgno_t);
+							else
+								psize += NODEDSZ(node);
+						}
+						psize = EVEN(psize);
+					}
+					if (psize > pmax || i == k-j) {
+						split_indx = i + (j<0);
+						break;
+					}
+				}
+			}
+			if (split_indx == newindx) {
+				sepkey.mv_size = newkey->mv_size;
+				sepkey.mv_data = newkey->mv_data;
+			} else {
+				node = (MDB_node *)((char *)mp + copy->mp_ptrs[split_indx]);
+				sepkey.mv_size = node->mn_ksize;
+				sepkey.mv_data = NODEKEY(node);
+			}
+		}
+	}
+
+	DPRINTF(("separator is %d [%s]", split_indx, DKEY(&sepkey)));
+
+	// Copy separator key to the parent.
+	if (SIZELEFT(mn.mc_pg[ptop]) < mdb_branch_size(env, &sepkey)) {
+		mn.mc_snum--;
+		mn.mc_top--;
+		did_split = 1;
+		rc = mdb_page_split(&mn, &sepkey, NULL, rp->mp_pgno, 0);
+
+		// root split?
+		if (mn.mc_snum == mc->mc_snum) {
+			mc->mc_pg[mc->mc_snum] = mc->mc_pg[mc->mc_top];
+			mc->mc_ki[mc->mc_snum] = mc->mc_ki[mc->mc_top];
+			mc->mc_pg[mc->mc_top] = mc->mc_pg[ptop];
+			mc->mc_ki[mc->mc_top] = mc->mc_ki[ptop];
+			mc->mc_snum++;
+			mc->mc_top++;
+			ptop++;
+		}
+		// Right page might now have changed parent.
+		// Check if left page also changed parent.
+		if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+		    mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+			for (i=0; i<ptop; i++) {
+				mc->mc_pg[i] = mn.mc_pg[i];
+				mc->mc_ki[i] = mn.mc_ki[i];
+			}
+			mc->mc_pg[ptop] = mn.mc_pg[ptop];
+			mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
+		}
+	} else {
+		mn.mc_top--;
+		rc = mdb_node_add(&mn, mn.mc_ki[ptop], &sepkey, NULL, rp->mp_pgno, 0);
+		mn.mc_top++;
+	}
+	mc->mc_flags ^= C_SPLITTING;
+	if (rc != MDB_SUCCESS) {
+		return rc;
+	}
+	if (nflags & MDB_APPEND) {
+		mc->mc_pg[mc->mc_top] = rp;
+		mc->mc_ki[mc->mc_top] = 0;
+		rc = mdb_node_add(mc, 0, newkey, newdata, newpgno, nflags);
+		if (rc)
+			return rc;
+		for (i=0; i<mc->mc_top; i++)
+			mc->mc_ki[i] = mn.mc_ki[i];
+	} else if (!IS_LEAF2(mp)) {
+		// Move nodes
+		mc->mc_pg[mc->mc_top] = rp;
+		i = split_indx;
+		j = 0;
+		do {
+			if (i == newindx) {
+				rkey.mv_data = newkey->mv_data;
+				rkey.mv_size = newkey->mv_size;
+				if (IS_LEAF(mp)) {
+					rdata = newdata;
+				} else
+					pgno = newpgno;
+				flags = nflags;
+				// Update index for the new key.
+				mc->mc_ki[mc->mc_top] = j;
+			} else {
+				node = (MDB_node *)((char *)mp + copy->mp_ptrs[i]);
+				rkey.mv_data = NODEKEY(node);
+				rkey.mv_size = node->mn_ksize;
+				if (IS_LEAF(mp)) {
+					xdata.mv_data = NODEDATA(node);
+					xdata.mv_size = NODEDSZ(node);
+					rdata = &xdata;
+				} else
+					pgno = NODEPGNO(node);
+				flags = node->mn_flags;
+			}
+
+			if (!IS_LEAF(mp) && j == 0) {
+				// First branch index doesn't need key data.
+				rkey.mv_size = 0;
+			}
+
+			rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
+			if (rc) {
+				// return tmp page to freelist
+				mdb_page_free(env, copy);
+				return rc;
+			}
+			if (i == nkeys) {
+				i = 0;
+				j = 0;
+				mc->mc_pg[mc->mc_top] = copy;
+			} else {
+				i++;
+				j++;
+			}
+		} while (i != split_indx);
+
+		nkeys = NUMKEYS(copy);
+		for (i=0; i<nkeys; i++)
+			mp->mp_ptrs[i] = copy->mp_ptrs[i];
+		mp->mp_lower = copy->mp_lower;
+		mp->mp_upper = copy->mp_upper;
+		memcpy(NODEPTR(mp, nkeys-1), NODEPTR(copy, nkeys-1),
+			env->me_psize - copy->mp_upper);
+
+		// reset back to original page
+		if (newindx < split_indx) {
+			mc->mc_pg[mc->mc_top] = mp;
+			if (nflags & MDB_RESERVE) {
+				node = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+				if (!(node->mn_flags & F_BIGDATA))
+					newdata->mv_data = NODEDATA(node);
+			}
+		} else {
+			mc->mc_pg[mc->mc_top] = rp;
+			mc->mc_ki[ptop]++;
+			// Make sure mc_ki is still valid.
+			if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+				mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+				for (i=0; i<ptop; i++) {
+					mc->mc_pg[i] = mn.mc_pg[i];
+					mc->mc_ki[i] = mn.mc_ki[i];
+				}
+				mc->mc_pg[ptop] = mn.mc_pg[ptop];
+				mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
+			}
+		}
+		// return tmp page to freelist
+		mdb_page_free(env, copy);
+	}
+
+	{
+		// Adjust other cursors pointing to mp
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = mc->mc_dbi;
+		int fixup = NUMKEYS(mp);
+
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (mc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3 == mc)
+				continue;
+			if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+				continue;
+			if (m3->mc_flags & C_SPLITTING)
+				continue;
+			if (new_root) {
+				int k;
+				// root split
+				for (k=m3->mc_top; k>=0; k--) {
+					m3->mc_ki[k+1] = m3->mc_ki[k];
+					m3->mc_pg[k+1] = m3->mc_pg[k];
+				}
+				if (m3->mc_ki[0] >= split_indx) {
+					m3->mc_ki[0] = 1;
+				} else {
+					m3->mc_ki[0] = 0;
+				}
+				m3->mc_pg[0] = mc->mc_pg[0];
+				m3->mc_snum++;
+				m3->mc_top++;
+			}
+			if (m3->mc_top >= mc->mc_top && m3->mc_pg[mc->mc_top] == mp) {
+				if (m3->mc_ki[mc->mc_top] >= newindx && !(nflags & MDB_SPLIT_REPLACE))
+					m3->mc_ki[mc->mc_top]++;
+				if (m3->mc_ki[mc->mc_top] >= fixup) {
+					m3->mc_pg[mc->mc_top] = rp;
+					m3->mc_ki[mc->mc_top] -= fixup;
+					m3->mc_ki[ptop] = mn.mc_ki[ptop];
+				}
+			} else if (!did_split && m3->mc_top >= ptop && m3->mc_pg[ptop] == mc->mc_pg[ptop] &&
+				m3->mc_ki[ptop] >= mc->mc_ki[ptop]) {
+				m3->mc_ki[ptop]++;
+			}
+		}
+	}
+	DPRINTF(("mp left: %d, rp left: %d", SIZELEFT(mp), SIZELEFT(rp)));
+	return rc;
+	*/
+	return nil
+}
+
+// Add all the DB's pages to the free list.
+// @param[in] mc Cursor on the DB to free.
+// @param[in] subs non-Zero to check for sub-DBs in this DB.
+// @return 0 on success, non-zero on failure.
+func (c *cursor) drop0(subs int) error {
+	/*
+	int rc;
+
+	rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
+	if (rc == MDB_SUCCESS) {
+		MDB_txn *txn = mc->mc_txn;
+		MDB_node *ni;
+		MDB_cursor mx;
+		unsigned int i;
+
+		// LEAF2 pages have no nodes, cannot have sub-DBs
+		if (IS_LEAF2(mc->mc_pg[mc->mc_top]))
+			mdb_cursor_pop(mc);
+
+		mdb_cursor_copy(mc, &mx);
+		while (mc->mc_snum > 0) {
+			MDB_page *mp = mc->mc_pg[mc->mc_top];
+			unsigned n = NUMKEYS(mp);
+			if (IS_LEAF(mp)) {
+				for (i=0; i<n; i++) {
+					ni = NODEPTR(mp, i);
+					if (ni->mn_flags & F_BIGDATA) {
+						MDB_page *omp;
+						pgno_t pg;
+						memcpy(&pg, NODEDATA(ni), sizeof(pg));
+						rc = mdb_page_get(txn, pg, &omp, NULL);
+						if (rc != 0)
+							return rc;
+						mdb_cassert(mc, IS_OVERFLOW(omp));
+						rc = mdb_midl_append_range(&txn->mt_free_pgs,
+							pg, omp->mp_pages);
+						if (rc)
+							return rc;
+					} else if (subs && (ni->mn_flags & F_SUBDATA)) {
+						mdb_xcursor_init1(mc, ni);
+						rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
+						if (rc)
+							return rc;
+					}
+				}
+			} else {
+				if ((rc = mdb_midl_need(&txn->mt_free_pgs, n)) != 0)
+					return rc;
+				for (i=0; i<n; i++) {
+					pgno_t pg;
+					ni = NODEPTR(mp, i);
+					pg = NODEPGNO(ni);
+					// free it
+					mdb_midl_xappend(txn->mt_free_pgs, pg);
+				}
+			}
+			if (!mc->mc_top)
+				break;
+			mc->mc_ki[mc->mc_top] = i;
+			rc = mdb_cursor_sibling(mc, 1);
+			if (rc) {
+				// no more siblings, go back to beginning
+				// of previous level.
+				mdb_cursor_pop(mc);
+				mc->mc_ki[0] = 0;
+				for (i=1; i<mc->mc_snum; i++) {
+					mc->mc_ki[i] = 0;
+					mc->mc_pg[i] = mx.mc_pg[i];
+				}
+			}
+		}
+		// free it
+		rc = mdb_midl_append(&txn->mt_free_pgs, mc->mc_db->md_root);
+	} else if (rc == MDB_NOTFOUND) {
+		rc = MDB_SUCCESS;
+	}
+	return rc;
+	*/
+	return nil
+}
diff --git a/db.go b/db.go
index 914cd18..2c593e7 100644
--- a/db.go
+++ b/db.go
@@ -8,12 +8,1177 @@ const (
 	IntegerDupKey
 )
 
+// TODO: #define	MDB_FATAL_ERROR	0x80000000U /** Failed to update the meta page. Probably an I/O error. */
+// TODO: #define	MDB_ENV_ACTIVE	0x20000000U /** Some fields are initialized. */
+// TODO: #define	MDB_ENV_TXKEY	0x10000000U /** me_txkey is set */
+// TODO: #define	MDB_LIVE_READER	0x08000000U /** Have liveness lock in reader table */
+
+// Only a subset of the @ref mdb_env flags can be changed
+// at runtime. Changing other flags requires closing the
+// environment and re-opening it with the new flags.
+// TODO: #define	CHANGEABLE	(MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
+// TODO: #define	CHANGELESS	(MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP| MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
+
 type DB interface {
 }
 
 type db struct {
+	sync.Mutex
+	file os.File
+	flags int
+	pageSize int
+	osPageSize int
+	readers []*reader
+	buckets []*bucket
+	xbuckets []*bucketx /**< array of static DB info */
+	bucketFlags []int /**< array of flags from MDB_db.md_flags */
+	path string
+	mmap []byte
+	mmapSize int /**< size of the data memory map */
+	size int /**< current file size */
+	meta1 []byte
+	meta2 []byte
+	pbuf []byte
+	transaction *transaction /**< current write transaction */
+	maxPageNumber int /**< me_mapsize / me_psize */
+	pageState pageStage /**< state of old pages from freeDB */
+	dpages []*page /**< list of malloc'd blocks for re-use */
+	freePageNumbers []int /** IDL of pages that became unused in a write txn */
+	dirtyPageNumbers []int /** ID2L of pages written during a write txn. Length MDB_IDL_UM_SIZE. */
+	maxFreeOnePage int /** Max number of freelist items that can fit in a single overflow page */
+	maxNodeSize int /** Max size of a node on a page */
+	maxKeySize int /**< max size of a key */
 }
 
 func NewDB() DB {
 	return &db{}
 }
+
+func (db *db) Path() string {
+	return db.path
+}
+
+func (db *db) freePage(p *page) {
+	/*
+	mp->mp_next = env->me_dpages;
+	VGMEMP_FREE(env, mp);
+	env->me_dpages = mp;
+	*/
+}
+
+func (db *db) freeDirtyPage(p *page) {
+	/*
+	if (!IS_OVERFLOW(dp) || dp->mp_pages == 1) {
+		mdb_page_free(env, dp);
+	} else {
+		// large pages just get freed directly
+		VGMEMP_FREE(env, dp);
+		free(dp);
+	}
+	*/
+}
+
+func (db *db) freeAllDirtyPages(p *page) {
+	/*
+	MDB_env *env = txn->mt_env;
+	MDB_ID2L dl = txn->mt_u.dirty_list;
+	unsigned i, n = dl[0].mid;
+
+	for (i = 1; i <= n; i++) {
+		mdb_dpage_free(env, dl[i].mptr);
+	}
+	dl[0].mid = 0;
+	*/
+}
+
+func (db *db) sync(force bool) error {
+	/*
+	int rc = 0;
+	if (force || !F_ISSET(env->me_flags, MDB_NOSYNC)) {
+		if (env->me_flags & MDB_WRITEMAP) {
+			int flags = ((env->me_flags & MDB_MAPASYNC) && !force)
+				? MS_ASYNC : MS_SYNC;
+			if (MDB_MSYNC(env->me_map, env->me_mapsize, flags))
+				rc = ErrCode();
+#ifdef _WIN32
+			else if (flags == MS_SYNC && MDB_FDATASYNC(env->me_fd))
+				rc = ErrCode();
+#endif
+		} else {
+			if (MDB_FDATASYNC(env->me_fd))
+				rc = ErrCode();
+		}
+	}
+	return rc;
+	*/
+	return nil
+}
+
+func (db *db) Transaction(parent *transaction, flags int) (*transaction, error) {
+	/*
+	MDB_txn *txn;
+	MDB_ntxn *ntxn;
+	int rc, size, tsize = sizeof(MDB_txn);
+
+	if (env->me_flags & MDB_FATAL_ERROR) {
+		DPUTS("environment had fatal error, must shutdown!");
+		return MDB_PANIC;
+	}
+	if ((env->me_flags & MDB_RDONLY) && !(flags & MDB_RDONLY))
+		return EACCES;
+	if (parent) {
+		// Nested transactions: Max 1 child, write txns only, no writemap
+		if (parent->mt_child ||
+			(flags & MDB_RDONLY) ||
+			(parent->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_ERROR)) ||
+			(env->me_flags & MDB_WRITEMAP))
+		{
+			return (parent->mt_flags & MDB_TXN_RDONLY) ? EINVAL : MDB_BAD_TXN;
+		}
+		tsize = sizeof(MDB_ntxn);
+	}
+	size = tsize + env->me_maxdbs * (sizeof(MDB_db)+1);
+	if (!(flags & MDB_RDONLY))
+		size += env->me_maxdbs * sizeof(MDB_cursor *);
+
+	if ((txn = calloc(1, size)) == NULL) {
+		DPRINTF(("calloc: %s", strerror(ErrCode())));
+		return ENOMEM;
+	}
+	txn->mt_dbs = (MDB_db *) ((char *)txn + tsize);
+	if (flags & MDB_RDONLY) {
+		txn->mt_flags |= MDB_TXN_RDONLY;
+		txn->mt_dbflags = (unsigned char *)(txn->mt_dbs + env->me_maxdbs);
+	} else {
+		txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
+		txn->mt_dbflags = (unsigned char *)(txn->mt_cursors + env->me_maxdbs);
+	}
+	txn->mt_env = env;
+
+	if (parent) {
+		unsigned int i;
+		txn->mt_u.dirty_list = malloc(sizeof(MDB_ID2)*MDB_IDL_UM_SIZE);
+		if (!txn->mt_u.dirty_list ||
+			!(txn->mt_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)))
+		{
+			free(txn->mt_u.dirty_list);
+			free(txn);
+			return ENOMEM;
+		}
+		txn->mt_txnid = parent->mt_txnid;
+		txn->mt_dirty_room = parent->mt_dirty_room;
+		txn->mt_u.dirty_list[0].mid = 0;
+		txn->mt_spill_pgs = NULL;
+		txn->mt_next_pgno = parent->mt_next_pgno;
+		parent->mt_child = txn;
+		txn->mt_parent = parent;
+		txn->mt_numdbs = parent->mt_numdbs;
+		txn->mt_flags = parent->mt_flags;
+		txn->mt_dbxs = parent->mt_dbxs;
+		memcpy(txn->mt_dbs, parent->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
+		// Copy parent's mt_dbflags, but clear DB_NEW
+		for (i=0; i<txn->mt_numdbs; i++)
+			txn->mt_dbflags[i] = parent->mt_dbflags[i] & ~DB_NEW;
+		rc = 0;
+		ntxn = (MDB_ntxn *)txn;
+		ntxn->mnt_pgstate = env->me_pgstate; // save parent me_pghead & co
+		if (env->me_pghead) {
+			size = MDB_IDL_SIZEOF(env->me_pghead);
+			env->me_pghead = mdb_midl_alloc(env->me_pghead[0]);
+			if (env->me_pghead)
+				memcpy(env->me_pghead, ntxn->mnt_pgstate.mf_pghead, size);
+			else
+				rc = ENOMEM;
+		}
+		if (!rc)
+			rc = mdb_cursor_shadow(parent, txn);
+		if (rc)
+			mdb_txn_reset0(txn, "beginchild-fail");
+	} else {
+		rc = mdb_txn_renew0(txn);
+	}
+	if (rc)
+		free(txn);
+	else {
+		*ret = txn;
+		DPRINTF(("begin txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+			txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
+			(void *) txn, (void *) env, txn->mt_dbs[MAIN_DBI].md_root));
+	}
+
+	return rc;
+	*/
+	return nil
+}
+
+// Read the environment parameters of a DB environment before
+// mapping it into memory.
+// @param[in] env the environment handle
+// @param[out] meta address of where to store the meta information
+// @return 0 on success, non-zero on failure.
+func (db *db) readHeader(meta *meta) error {
+	/*
+	MDB_metabuf	pbuf;
+	MDB_page	*p;
+	MDB_meta	*m;
+	int			i, rc, off;
+	enum { Size = sizeof(pbuf) };
+
+	// We don't know the page size yet, so use a minimum value.
+	// Read both meta pages so we can use the latest one.
+
+	for (i=off=0; i<2; i++, off = meta->mm_psize) {
+#ifdef _WIN32
+		DWORD len;
+		OVERLAPPED ov;
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		rc = ReadFile(env->me_fd, &pbuf, Size, &len, &ov) ? (int)len : -1;
+		if (rc == -1 && ErrCode() == ERROR_HANDLE_EOF)
+			rc = 0;
+#else
+		rc = pread(env->me_fd, &pbuf, Size, off);
+#endif
+		if (rc != Size) {
+			if (rc == 0 && off == 0)
+				return ENOENT;
+			rc = rc < 0 ? (int) ErrCode() : MDB_INVALID;
+			DPRINTF(("read: %s", mdb_strerror(rc)));
+			return rc;
+		}
+
+		p = (MDB_page *)&pbuf;
+
+		if (!F_ISSET(p->mp_flags, P_META)) {
+			DPRINTF(("page %"Z"u not a meta page", p->mp_pgno));
+			return MDB_INVALID;
+		}
+
+		m = METADATA(p);
+		if (m->mm_magic != MDB_MAGIC) {
+			DPUTS("meta has invalid magic");
+			return MDB_INVALID;
+		}
+
+		if (m->mm_version != MDB_DATA_VERSION) {
+			DPRINTF(("database is version %u, expected version %u",
+				m->mm_version, MDB_DATA_VERSION));
+			return MDB_VERSION_MISMATCH;
+		}
+
+		if (off == 0 || m->mm_txnid > meta->mm_txnid)
+			*meta = *m;
+	}
+	return 0;
+	*/
+	return nil
+}
+
+// Write the environment parameters of a freshly created DB environment.
+// @param[in] env the environment handle
+// @param[out] meta address of where to store the meta information
+// @return 0 on success, non-zero on failure.
+func (db *db) initMeta(meta *meta) error {
+	/*
+	MDB_page *p, *q;
+	int rc;
+	unsigned int	 psize;
+#ifdef _WIN32
+	DWORD len;
+	OVERLAPPED ov;
+	memset(&ov, 0, sizeof(ov));
+#define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
+	ov.Offset = pos;	\
+	rc = WriteFile(fd, ptr, size, &len, &ov);	} while(0)
+#else
+	int len;
+#define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
+	len = pwrite(fd, ptr, size, pos);	\
+	rc = (len >= 0); } while(0)
+#endif
+
+	DPUTS("writing new meta page");
+
+	psize = env->me_psize;
+
+	meta->mm_magic = MDB_MAGIC;
+	meta->mm_version = MDB_DATA_VERSION;
+	meta->mm_mapsize = env->me_mapsize;
+	meta->mm_psize = psize;
+	meta->mm_last_pg = 1;
+	meta->mm_flags = env->me_flags & 0xffff;
+	meta->mm_flags |= MDB_INTEGERKEY;
+	meta->mm_dbs[0].md_root = P_INVALID;
+	meta->mm_dbs[1].md_root = P_INVALID;
+
+	p = calloc(2, psize);
+	p->mp_pgno = 0;
+	p->mp_flags = P_META;
+	*(MDB_meta *)METADATA(p) = *meta;
+
+	q = (MDB_page *)((char *)p + psize);
+	q->mp_pgno = 1;
+	q->mp_flags = P_META;
+	*(MDB_meta *)METADATA(q) = *meta;
+
+	DO_PWRITE(rc, env->me_fd, p, psize * 2, len, 0);
+	if (!rc)
+		rc = ErrCode();
+	else if ((unsigned) len == psize * 2)
+		rc = MDB_SUCCESS;
+	else
+		rc = ENOSPC;
+	free(p);
+	return rc;
+	*/
+	return nil
+}
+
+// Check both meta pages to see which one is newer.
+// @param[in] env the environment handle
+// @return meta toggle (0 or 1).
+func (db *db) pickMeta() int {
+	/*
+	return (env->me_metas[0]->mm_txnid < env->me_metas[1]->mm_txnid);
+	*/
+	return 0
+}
+
+func (db *db) Create() error {
+	/*
+	MDB_env *e;
+
+	e = calloc(1, sizeof(MDB_env));
+	if (!e)
+		return ENOMEM;
+
+	e->me_maxreaders = DEFAULT_READERS;
+	e->me_maxdbs = e->me_numdbs = 2;
+	e->me_fd = INVALID_HANDLE_VALUE;
+	e->me_lfd = INVALID_HANDLE_VALUE;
+	e->me_mfd = INVALID_HANDLE_VALUE;
+#ifdef MDB_USE_POSIX_SEM
+	e->me_rmutex = SEM_FAILED;
+	e->me_wmutex = SEM_FAILED;
+#endif
+	e->me_pid = getpid();
+	GET_PAGESIZE(e->me_os_psize);
+	VGMEMP_CREATE(e,0,0);
+	*env = e;
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// int mdb_env_map(MDB_env *env, void *addr, int newsize)
+func (db *db) openMmap(newsize int) {
+	/*
+	MDB_page *p;
+	unsigned int flags = env->me_flags;
+#ifdef _WIN32
+	int rc;
+	HANDLE mh;
+	LONG sizelo, sizehi;
+	sizelo = env->me_mapsize & 0xffffffff;
+	sizehi = env->me_mapsize >> 16 >> 16; // only needed on Win64
+
+	// Windows won't create mappings for zero length files.
+	// Just allocate the maxsize right now.
+	if (newsize) {
+		if (SetFilePointer(env->me_fd, sizelo, &sizehi, 0) != (DWORD)sizelo
+			|| !SetEndOfFile(env->me_fd)
+			|| SetFilePointer(env->me_fd, 0, NULL, 0) != 0)
+			return ErrCode();
+	}
+	mh = CreateFileMapping(env->me_fd, NULL, flags & MDB_WRITEMAP ?
+		PAGE_READWRITE : PAGE_READONLY,
+		sizehi, sizelo, NULL);
+	if (!mh)
+		return ErrCode();
+	env->me_map = MapViewOfFileEx(mh, flags & MDB_WRITEMAP ?
+		FILE_MAP_WRITE : FILE_MAP_READ,
+		0, 0, env->me_mapsize, addr);
+	rc = env->me_map ? 0 : ErrCode();
+	CloseHandle(mh);
+	if (rc)
+		return rc;
+#else
+	int prot = PROT_READ;
+	if (flags & MDB_WRITEMAP) {
+		prot |= PROT_WRITE;
+		if (ftruncate(env->me_fd, env->me_mapsize) < 0)
+			return ErrCode();
+	}
+	env->me_map = mmap(addr, env->me_mapsize, prot, MAP_SHARED,
+		env->me_fd, 0);
+	if (env->me_map == MAP_FAILED) {
+		env->me_map = NULL;
+		return ErrCode();
+	}
+
+	if (flags & MDB_NORDAHEAD) {
+		// Turn off readahead. It's harmful when the DB is larger than RAM.
+#ifdef MADV_RANDOM
+		madvise(env->me_map, env->me_mapsize, MADV_RANDOM);
+#else
+#ifdef POSIX_MADV_RANDOM
+		posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_RANDOM);
+#endif // POSIX_MADV_RANDOM
+#endif // MADV_RANDOM
+	}
+#endif // _WIN32
+
+	// Can happen because the address argument to mmap() is just a
+	// hint.  mmap() can pick another, e.g. if the range is in use.
+	// The MAP_FIXED flag would prevent that, but then mmap could
+	// instead unmap existing pages to make room for the new map.
+	if (addr && env->me_map != addr)
+		return EBUSY;	// TODO: Make a new MDB_* error code?
+
+	p = (MDB_page *)env->me_map;
+	env->me_metas[0] = METADATA(p);
+	env->me_metas[1] = (MDB_meta *)((char *)env->me_metas[0] + env->me_psize);
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (db *db) setMapSize(size int) error {
+	/*
+	// If env is already open, caller is responsible for making
+	// sure there are no active txns.
+	if (env->me_map) {
+		int rc;
+		void *old;
+		if (env->me_txn)
+			return EINVAL;
+		if (!size)
+			size = env->me_metas[mdb_env_pick_meta(env)]->mm_mapsize;
+		else if (size < env->me_mapsize) {
+			// If the configured size is smaller, make sure it's
+			// still big enough. Silently round up to minimum if not.
+			size_t minsize = (env->me_metas[mdb_env_pick_meta(env)]->mm_last_pg + 1) * env->me_psize;
+			if (size < minsize)
+				size = minsize;
+		}
+		munmap(env->me_map, env->me_mapsize);
+		env->me_mapsize = size;
+		old = (env->me_flags & MDB_FIXEDMAP) ? env->me_map : NULL;
+		rc = mdb_env_map(env, old, 1);
+		if (rc)
+			return rc;
+	}
+	env->me_mapsize = size;
+	if (env->me_psize)
+		env->me_maxpg = env->me_mapsize / env->me_psize;
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (db *db) setMaxBucketCount(count int) error {
+	/*
+	if (env->me_map)
+		return EINVAL;
+	env->me_maxdbs = dbs + 2; // Named databases + main and free DB
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (db *db) setMaxReaderCount(count int) error {
+	/*
+	if (env->me_map || readers < 1)
+		return EINVAL;
+	env->me_maxreaders = readers;
+	return MDB_SUCCESS;
+	*/
+}
+
+func (db *db) getMaxReaderCount(count int) (int, error) {
+	/*
+	if (!env || !readers)
+		return EINVAL;
+	*readers = env->me_maxreaders;
+	return MDB_SUCCESS;
+	*/
+	return 0, nil
+}
+
+// Further setup required for opening an MDB environment
+func (db *db) open() error {
+	/*
+	unsigned int flags = env->me_flags;
+	int i, newenv = 0, rc;
+	MDB_meta meta;
+
+#ifdef _WIN32
+	// See if we should use QueryLimited
+	rc = GetVersion();
+	if ((rc & 0xff) > 5)
+		env->me_pidquery = MDB_PROCESS_QUERY_LIMITED_INFORMATION;
+	else
+		env->me_pidquery = PROCESS_QUERY_INFORMATION;
+#endif // _WIN32
+
+	memset(&meta, 0, sizeof(meta));
+
+	if ((i = mdb_env_read_header(env, &meta)) != 0) {
+		if (i != ENOENT)
+			return i;
+		DPUTS("new mdbenv");
+		newenv = 1;
+		env->me_psize = env->me_os_psize;
+		if (env->me_psize > MAX_PAGESIZE)
+			env->me_psize = MAX_PAGESIZE;
+	} else {
+		env->me_psize = meta.mm_psize;
+	}
+
+	// Was a mapsize configured?
+	if (!env->me_mapsize) {
+		// If this is a new environment, take the default,
+		// else use the size recorded in the existing env.
+		env->me_mapsize = newenv ? DEFAULT_MAPSIZE : meta.mm_mapsize;
+	} else if (env->me_mapsize < meta.mm_mapsize) {
+		// If the configured size is smaller, make sure it's
+		// still big enough. Silently round up to minimum if not.
+		size_t minsize = (meta.mm_last_pg + 1) * meta.mm_psize;
+		if (env->me_mapsize < minsize)
+			env->me_mapsize = minsize;
+	}
+
+	rc = mdb_env_map(env, meta.mm_address, newenv);
+	if (rc)
+		return rc;
+
+	if (newenv) {
+		if (flags & MDB_FIXEDMAP)
+			meta.mm_address = env->me_map;
+		i = mdb_env_init_meta(env, &meta);
+		if (i != MDB_SUCCESS) {
+			return i;
+		}
+	}
+
+	env->me_maxfree_1pg = (env->me_psize - PAGEHDRSZ) / sizeof(pgno_t) - 1;
+	env->me_nodemax = (((env->me_psize - PAGEHDRSZ) / MDB_MINKEYS) & -2)
+		- sizeof(indx_t);
+#if !(MDB_MAXKEYSIZE)
+	env->me_maxkey = env->me_nodemax - (NODESIZE + sizeof(MDB_db));
+#endif
+	env->me_maxpg = env->me_mapsize / env->me_psize;
+
+#if MDB_DEBUG
+	{
+		int toggle = mdb_env_pick_meta(env);
+		MDB_db *db = &env->me_metas[toggle]->mm_dbs[MAIN_DBI];
+
+		DPRINTF(("opened database version %u, pagesize %u",
+			env->me_metas[0]->mm_version, env->me_psize));
+		DPRINTF(("using meta page %d",    toggle));
+		DPRINTF(("depth: %u",             db->md_depth));
+		DPRINTF(("entries: %"Z"u",        db->md_entries));
+		DPRINTF(("branch pages: %"Z"u",   db->md_branch_pages));
+		DPRINTF(("leaf pages: %"Z"u",     db->md_leaf_pages));
+		DPRINTF(("overflow pages: %"Z"u", db->md_overflow_pages));
+		DPRINTF(("root: %"Z"u",           db->md_root));
+	}
+#endif
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (db *db) Open(path string, flags int, mode uint) error {
+	/*
+	int		oflags, rc, len, excl = -1;
+	char *lpath, *dpath;
+
+	if (env->me_fd!=INVALID_HANDLE_VALUE || (flags & ~(CHANGEABLE|CHANGELESS)))
+		return EINVAL;
+
+	len = strlen(path);
+	if (flags & MDB_NOSUBDIR) {
+		rc = len + sizeof(LOCKSUFF) + len + 1;
+	} else {
+		rc = len + sizeof(LOCKNAME) + len + sizeof(DATANAME);
+	}
+	lpath = malloc(rc);
+	if (!lpath)
+		return ENOMEM;
+	if (flags & MDB_NOSUBDIR) {
+		dpath = lpath + len + sizeof(LOCKSUFF);
+		sprintf(lpath, "%s" LOCKSUFF, path);
+		strcpy(dpath, path);
+	} else {
+		dpath = lpath + len + sizeof(LOCKNAME);
+		sprintf(lpath, "%s" LOCKNAME, path);
+		sprintf(dpath, "%s" DATANAME, path);
+	}
+
+	rc = MDB_SUCCESS;
+	flags |= env->me_flags;
+	if (flags & MDB_RDONLY) {
+		// silently ignore WRITEMAP when we're only getting read access
+		flags &= ~MDB_WRITEMAP;
+	} else {
+		if (!((env->me_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)) &&
+			  (env->me_dirty_list = calloc(MDB_IDL_UM_SIZE, sizeof(MDB_ID2)))))
+			rc = ENOMEM;
+	}
+	env->me_flags = flags |= MDB_ENV_ACTIVE;
+	if (rc)
+		goto leave;
+
+	env->me_path = strdup(path);
+	env->me_dbxs = calloc(env->me_maxdbs, sizeof(MDB_dbx));
+	env->me_dbflags = calloc(env->me_maxdbs, sizeof(uint16_t));
+	if (!(env->me_dbxs && env->me_path && env->me_dbflags)) {
+		rc = ENOMEM;
+		goto leave;
+	}
+
+	// For RDONLY, get lockfile after we know datafile exists
+	if (!(flags & (MDB_RDONLY|MDB_NOLOCK))) {
+		rc = mdb_env_setup_locks(env, lpath, mode, &excl);
+		if (rc)
+			goto leave;
+	}
+
+#ifdef _WIN32
+	if (F_ISSET(flags, MDB_RDONLY)) {
+		oflags = GENERIC_READ;
+		len = OPEN_EXISTING;
+	} else {
+		oflags = GENERIC_READ|GENERIC_WRITE;
+		len = OPEN_ALWAYS;
+	}
+	mode = FILE_ATTRIBUTE_NORMAL;
+	env->me_fd = CreateFile(dpath, oflags, FILE_SHARE_READ|FILE_SHARE_WRITE,
+		NULL, len, mode, NULL);
+#else
+	if (F_ISSET(flags, MDB_RDONLY))
+		oflags = O_RDONLY;
+	else
+		oflags = O_RDWR | O_CREAT;
+
+	env->me_fd = open(dpath, oflags, mode);
+#endif
+	if (env->me_fd == INVALID_HANDLE_VALUE) {
+		rc = ErrCode();
+		goto leave;
+	}
+
+	if ((flags & (MDB_RDONLY|MDB_NOLOCK)) == MDB_RDONLY) {
+		rc = mdb_env_setup_locks(env, lpath, mode, &excl);
+		if (rc)
+			goto leave;
+	}
+
+	if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) {
+		if (flags & (MDB_RDONLY|MDB_WRITEMAP)) {
+			env->me_mfd = env->me_fd;
+		} else {
+			// Synchronous fd for meta writes. Needed even with
+			// MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
+#ifdef _WIN32
+			len = OPEN_EXISTING;
+			env->me_mfd = CreateFile(dpath, oflags,
+				FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, len,
+				mode | FILE_FLAG_WRITE_THROUGH, NULL);
+#else
+			oflags &= ~O_CREAT;
+			env->me_mfd = open(dpath, oflags | MDB_DSYNC, mode);
+#endif
+			if (env->me_mfd == INVALID_HANDLE_VALUE) {
+				rc = ErrCode();
+				goto leave;
+			}
+		}
+		DPRINTF(("opened dbenv %p", (void *) env));
+		if (excl > 0) {
+			rc = mdb_env_share_locks(env, &excl);
+			if (rc)
+				goto leave;
+		}
+		if (!((flags & MDB_RDONLY) ||
+			  (env->me_pbuf = calloc(1, env->me_psize))))
+			rc = ENOMEM;
+	}
+
+leave:
+	if (rc) {
+		mdb_env_close0(env, excl);
+	}
+	free(lpath);
+	return rc;
+	*/
+	return nil
+}
+
+// Destroy resources from mdb_env_open(), clear our readers & DBIs
+func (db *db) close0(excl) {
+	/*
+	int i;
+
+	if (!(env->me_flags & MDB_ENV_ACTIVE))
+		return;
+
+	// Doing this here since me_dbxs may not exist during mdb_env_close
+	for (i = env->me_maxdbs; --i > MAIN_DBI; )
+		free(env->me_dbxs[i].md_name.mv_data);
+
+	free(env->me_pbuf);
+	free(env->me_dbflags);
+	free(env->me_dbxs);
+	free(env->me_path);
+	free(env->me_dirty_list);
+	mdb_midl_free(env->me_free_pgs);
+
+	if (env->me_flags & MDB_ENV_TXKEY) {
+		pthread_key_delete(env->me_txkey);
+#ifdef _WIN32
+		// Delete our key from the global list
+		for (i=0; i<mdb_tls_nkeys; i++)
+			if (mdb_tls_keys[i] == env->me_txkey) {
+				mdb_tls_keys[i] = mdb_tls_keys[mdb_tls_nkeys-1];
+				mdb_tls_nkeys--;
+				break;
+			}
+#endif
+	}
+
+	if (env->me_map) {
+		munmap(env->me_map, env->me_mapsize);
+	}
+	if (env->me_mfd != env->me_fd && env->me_mfd != INVALID_HANDLE_VALUE)
+		(void) close(env->me_mfd);
+	if (env->me_fd != INVALID_HANDLE_VALUE)
+		(void) close(env->me_fd);
+	if (env->me_txns) {
+		MDB_PID_T pid = env->me_pid;
+		// Clearing readers is done in this function because
+		// me_txkey with its destructor must be disabled first.
+		for (i = env->me_numreaders; --i >= 0; )
+			if (env->me_txns->mti_readers[i].mr_pid == pid)
+				env->me_txns->mti_readers[i].mr_pid = 0;
+#ifdef _WIN32
+		if (env->me_rmutex) {
+			CloseHandle(env->me_rmutex);
+			if (env->me_wmutex) CloseHandle(env->me_wmutex);
+		}
+		// Windows automatically destroys the mutexes when
+		// the last handle closes.
+#elif defined(MDB_USE_POSIX_SEM)
+		if (env->me_rmutex != SEM_FAILED) {
+			sem_close(env->me_rmutex);
+			if (env->me_wmutex != SEM_FAILED)
+				sem_close(env->me_wmutex);
+			// If we have the filelock:  If we are the
+			// only remaining user, clean up semaphores.
+			if (excl == 0)
+				mdb_env_excl_lock(env, &excl);
+			if (excl > 0) {
+				sem_unlink(env->me_txns->mti_rmname);
+				sem_unlink(env->me_txns->mti_wmname);
+			}
+		}
+#endif
+		munmap((void *)env->me_txns, (env->me_maxreaders-1)*sizeof(MDB_reader)+sizeof(MDB_txninfo));
+	}
+	if (env->me_lfd != INVALID_HANDLE_VALUE) {
+#ifdef _WIN32
+		if (excl >= 0) {
+			// Unlock the lockfile.  Windows would have unlocked it
+			// after closing anyway, but not necessarily at once.
+			UnlockFile(env->me_lfd, 0, 0, 1, 0);
+		}
+#endif
+		(void) close(env->me_lfd);
+	}
+
+	env->me_flags &= ~(MDB_ENV_ACTIVE|MDB_ENV_TXKEY);
+	*/
+}
+
+func (db *db) copyfd(handle int) error {
+	/*
+	MDB_txn *txn = NULL;
+	int rc;
+	size_t wsize;
+	char *ptr;
+#ifdef _WIN32
+	DWORD len, w2;
+#define DO_WRITE(rc, fd, ptr, w2, len)	rc = WriteFile(fd, ptr, w2, &len, NULL)
+#else
+	ssize_t len;
+	size_t w2;
+#define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
+#endif
+
+	// Do the lock/unlock of the reader mutex before starting the
+	// write txn.  Otherwise other read txns could block writers.
+	rc = mdb_txn_begin(env, NULL, MDB_RDONLY, &txn);
+	if (rc)
+		return rc;
+
+	if (env->me_txns) {
+		// We must start the actual read txn after blocking writers
+		mdb_txn_reset0(txn, "reset-stage1");
+
+		// Temporarily block writers until we snapshot the meta pages
+		LOCK_MUTEX_W(env);
+
+		rc = mdb_txn_renew0(txn);
+		if (rc) {
+			UNLOCK_MUTEX_W(env);
+			goto leave;
+		}
+	}
+
+	wsize = env->me_psize * 2;
+	ptr = env->me_map;
+	w2 = wsize;
+	while (w2 > 0) {
+		DO_WRITE(rc, fd, ptr, w2, len);
+		if (!rc) {
+			rc = ErrCode();
+			break;
+		} else if (len > 0) {
+			rc = MDB_SUCCESS;
+			ptr += len;
+			w2 -= len;
+			continue;
+		} else {
+			// Non-blocking or async handles are not supported
+			rc = EIO;
+			break;
+		}
+	}
+	if (env->me_txns)
+		UNLOCK_MUTEX_W(env);
+
+	if (rc)
+		goto leave;
+
+	wsize = txn->mt_next_pgno * env->me_psize - wsize;
+	while (wsize > 0) {
+		if (wsize > MAX_WRITE)
+			w2 = MAX_WRITE;
+		else
+			w2 = wsize;
+		DO_WRITE(rc, fd, ptr, w2, len);
+		if (!rc) {
+			rc = ErrCode();
+			break;
+		} else if (len > 0) {
+			rc = MDB_SUCCESS;
+			ptr += len;
+			wsize -= len;
+			continue;
+		} else {
+			rc = EIO;
+			break;
+		}
+	}
+
+leave:
+	mdb_txn_abort(txn);
+	return rc;
+}
+
+int
+mdb_env_copy(MDB_env *env, const char *path)
+{
+	int rc, len;
+	char *lpath;
+	HANDLE newfd = INVALID_HANDLE_VALUE;
+
+	if (env->me_flags & MDB_NOSUBDIR) {
+		lpath = (char *)path;
+	} else {
+		len = strlen(path);
+		len += sizeof(DATANAME);
+		lpath = malloc(len);
+		if (!lpath)
+			return ENOMEM;
+		sprintf(lpath, "%s" DATANAME, path);
+	}
+
+	// The destination path must exist, but the destination file must not.
+	// We don't want the OS to cache the writes, since the source data is
+	// already in the OS cache.
+#ifdef _WIN32
+	newfd = CreateFile(lpath, GENERIC_WRITE, 0, NULL, CREATE_NEW,
+				FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH, NULL);
+#else
+	newfd = open(lpath, O_WRONLY|O_CREAT|O_EXCL, 0666);
+#endif
+	if (newfd == INVALID_HANDLE_VALUE) {
+		rc = ErrCode();
+		goto leave;
+	}
+
+#ifdef O_DIRECT
+	// Set O_DIRECT if the file system supports it
+	if ((rc = fcntl(newfd, F_GETFL)) != -1)
+		(void) fcntl(newfd, F_SETFL, rc | O_DIRECT);
+#endif
+#ifdef F_NOCACHE	// __APPLE__
+	rc = fcntl(newfd, F_NOCACHE, 1);
+	if (rc) {
+		rc = ErrCode();
+		goto leave;
+	}
+#endif
+
+	rc = mdb_env_copyfd(env, newfd);
+
+leave:
+	if (!(env->me_flags & MDB_NOSUBDIR))
+		free(lpath);
+	if (newfd != INVALID_HANDLE_VALUE)
+		if (close(newfd) < 0 && rc == MDB_SUCCESS)
+			rc = ErrCode();
+
+	return rc;
+	*/
+	return nil
+}
+
+func (db *db) Close() {
+	/*
+	MDB_page *dp;
+
+	if (env == NULL)
+		return;
+
+	VGMEMP_DESTROY(env);
+	while ((dp = env->me_dpages) != NULL) {
+		VGMEMP_DEFINED(&dp->mp_next, sizeof(dp->mp_next));
+		env->me_dpages = dp->mp_next;
+		free(dp);
+	}
+
+	mdb_env_close0(env, 0);
+	free(env);
+	*/
+}
+
+// Calculate the size of a leaf node.
+// The size depends on the environment's page size; if a data item
+// is too large it will be put onto an overflow page and the node
+// size will only include the key and not the data. Sizes are always
+// rounded up to an even number of bytes, to guarantee 2-byte alignment
+// of the #MDB_node headers.
+// @param[in] env The environment handle.
+// @param[in] key The key for the node.
+// @param[in] data The data for the node.
+// @return The number of bytes needed to store the node.
+func (db *db) LeafSize(key []byte, data []byte) int {
+	/*
+	size_t		 sz;
+
+	sz = LEAFSIZE(key, data);
+	if (sz > env->me_nodemax) {
+		// put on overflow page
+		sz -= data->mv_size - sizeof(pgno_t);
+	}
+
+	return EVEN(sz + sizeof(indx_t));
+	*/
+	return 0
+}
+
+// Calculate the size of a branch node.
+// The size should depend on the environment's page size but since
+// we currently don't support spilling large keys onto overflow
+// pages, it's simply the size of the #MDB_node header plus the
+// size of the key. Sizes are always rounded up to an even number
+// of bytes, to guarantee 2-byte alignment of the #MDB_node headers.
+// @param[in] env The environment handle.
+// @param[in] key The key for the node.
+// @return The number of bytes needed to store the node.
+func (db *db) BranchSize(key []byte) int {
+	/*
+	size_t		 sz;
+
+	sz = INDXSIZE(key);
+	if (sz > env->me_nodemax) {
+		// put on overflow page
+		// not implemented
+		// sz -= key->size - sizeof(pgno_t);
+	}
+
+	return sz + sizeof(indx_t);
+	*/
+	return 0
+}
+
+func (db *db) SetFlags(flag int, onoff bool) error {
+	/*
+	if ((flag & CHANGEABLE) != flag)
+		return EINVAL;
+	if (onoff)
+		env->me_flags |= flag;
+	else
+		env->me_flags &= ~flag;
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (db *db) Flags() int {
+	return db.flags
+}
+
+
+func (db *db) Stat() *Stat
+	/*
+	int toggle;
+
+	if (env == NULL || arg == NULL)
+		return EINVAL;
+
+	toggle = mdb_env_pick_meta(env);
+	stat := &Stat{}
+	stat->ms_psize = env->me_psize;
+	stat->ms_depth = db->md_depth;
+	stat->ms_branch_pages = db->md_branch_pages;
+	stat->ms_leaf_pages = db->md_leaf_pages;
+	stat->ms_overflow_pages = db->md_overflow_pages;
+	stat->ms_entries = db->md_entries;
+
+	//return mdb_stat0(env, &env->me_metas[toggle]->mm_dbs[MAIN_DBI], stat);
+	return stat
+	*/
+}
+
+func (db *db) Info() *Info {
+	/*
+	int toggle;
+
+	if (env == NULL || arg == NULL)
+		return EINVAL;
+
+	toggle = mdb_env_pick_meta(env);
+	arg->me_mapaddr = (env->me_flags & MDB_FIXEDMAP) ? env->me_map : 0;
+	arg->me_mapsize = env->me_mapsize;
+	arg->me_maxreaders = env->me_maxreaders;
+
+	// me_numreaders may be zero if this process never used any readers. Use
+	// the shared numreader count if it exists.
+	arg->me_numreaders = env->me_txns ? env->me_txns->mti_numreaders : env->me_numreaders;
+
+	arg->me_last_pgno = env->me_metas[toggle]->mm_last_pg;
+	arg->me_last_txnid = env->me_metas[toggle]->mm_txnid;
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// TODO: Move to bucket.go
+func (db *db) CloseBucket(b Bucket) {
+	/*
+	char *ptr;
+	if (dbi <= MAIN_DBI || dbi >= env->me_maxdbs)
+		return;
+	ptr = env->me_dbxs[dbi].md_name.mv_data;
+	env->me_dbxs[dbi].md_name.mv_data = NULL;
+	env->me_dbxs[dbi].md_name.mv_size = 0;
+	env->me_dbflags[dbi] = 0;
+	free(ptr);
+	*/
+}
+
+//int mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx)
+func (db *db) getReaderList() error {
+	/*
+	unsigned int i, rdrs;
+	MDB_reader *mr;
+	char buf[64];
+	int rc = 0, first = 1;
+
+	if (!env || !func)
+		return -1;
+	if (!env->me_txns) {
+		return func("(no reader locks)\n", ctx);
+	}
+	rdrs = env->me_txns->mti_numreaders;
+	mr = env->me_txns->mti_readers;
+	for (i=0; i<rdrs; i++) {
+		if (mr[i].mr_pid) {
+			txnid_t	txnid = mr[i].mr_txnid;
+			sprintf(buf, txnid == (txnid_t)-1 ?
+				"%10d %"Z"x -\n" : "%10d %"Z"x %"Z"u\n",
+				(int)mr[i].mr_pid, (size_t)mr[i].mr_tid, txnid);
+			if (first) {
+				first = 0;
+				rc = func("    pid     thread     txnid\n", ctx);
+				if (rc < 0)
+					break;
+			}
+			rc = func(buf, ctx);
+			if (rc < 0)
+				break;
+		}
+	}
+	if (first) {
+		rc = func("(no active readers)\n", ctx);
+	}
+	return rc;
+	*/
+	return nil
+}
+
+// (bool return is whether reader is dead)
+func (db *db) checkReaders() (bool, error) {
+	/*
+	unsigned int i, j, rdrs;
+	MDB_reader *mr;
+	MDB_PID_T *pids, pid;
+	int count = 0;
+
+	if (!env)
+		return EINVAL;
+	if (dead)
+		*dead = 0;
+	if (!env->me_txns)
+		return MDB_SUCCESS;
+	rdrs = env->me_txns->mti_numreaders;
+	pids = malloc((rdrs+1) * sizeof(MDB_PID_T));
+	if (!pids)
+		return ENOMEM;
+	pids[0] = 0;
+	mr = env->me_txns->mti_readers;
+	for (i=0; i<rdrs; i++) {
+		if (mr[i].mr_pid && mr[i].mr_pid != env->me_pid) {
+			pid = mr[i].mr_pid;
+			if (mdb_pid_insert(pids, pid) == 0) {
+				if (!mdb_reader_pid(env, Pidcheck, pid)) {
+					LOCK_MUTEX_R(env);
+					// Recheck, a new process may have reused pid
+					if (!mdb_reader_pid(env, Pidcheck, pid)) {
+						for (j=i; j<rdrs; j++)
+							if (mr[j].mr_pid == pid) {
+								DPRINTF(("clear stale reader pid %u txn %"Z"d",
+									(unsigned) pid, mr[j].mr_txnid));
+								mr[j].mr_pid = 0;
+								count++;
+							}
+					}
+					UNLOCK_MUTEX_R(env);
+				}
+			}
+		}
+	}
+	free(pids);
+	if (dead)
+		*dead = count;
+	return MDB_SUCCESS;
+	*/
+	return false, nil
+}
diff --git a/node.go b/node.go
index 38b0293..928e0c9 100644
--- a/node.go
+++ b/node.go
@@ -38,3 +38,54 @@ func (n *node) size() int {
 
 // TODO: #define MDB_GET_KEY(node, keyptr)	{ if ((keyptr) != NULL) { (keyptr)->mv_size = NODEKSZ(node); (keyptr)->mv_data = NODEKEY(node); } }
 // TODO: #define MDB_GET_KEY2(node, key)	{ key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
+
+// Compact the main page after deleting a node on a subpage.
+// @param[in] mp The main page to operate on.
+// @param[in] indx The index of the subpage on the main page.
+func (n *node) shrink(index int) {
+	/*
+	MDB_node *node;
+	MDB_page *sp, *xp;
+	char *base;
+	int nsize, delta;
+	indx_t		 i, numkeys, ptr;
+
+	node = NODEPTR(mp, indx);
+	sp = (MDB_page *)NODEDATA(node);
+	delta = SIZELEFT(sp);
+	xp = (MDB_page *)((char *)sp + delta);
+
+	// shift subpage upward
+	if (IS_LEAF2(sp)) {
+		nsize = NUMKEYS(sp) * sp->mp_pad;
+		if (nsize & 1)
+			return;		// do not make the node uneven-sized
+		memmove(METADATA(xp), METADATA(sp), nsize);
+	} else {
+		int i;
+		numkeys = NUMKEYS(sp);
+		for (i=numkeys-1; i>=0; i--)
+			xp->mp_ptrs[i] = sp->mp_ptrs[i] - delta;
+	}
+	xp->mp_upper = sp->mp_lower;
+	xp->mp_lower = sp->mp_lower;
+	xp->mp_flags = sp->mp_flags;
+	xp->mp_pad = sp->mp_pad;
+	COPY_PGNO(xp->mp_pgno, mp->mp_pgno);
+
+	nsize = NODEDSZ(node) - delta;
+	SETDSZ(node, nsize);
+
+	// shift lower nodes upward
+	ptr = mp->mp_ptrs[indx];
+	numkeys = NUMKEYS(mp);
+	for (i = 0; i < numkeys; i++) {
+		if (mp->mp_ptrs[i] <= ptr)
+			mp->mp_ptrs[i] += delta;
+	}
+
+	base = (char *)mp + mp->mp_upper;
+	memmove(base + delta, base, ptr - mp->mp_upper + NODESIZE + NODEKSZ(node));
+	mp->mp_upper += delta;
+	*/
+}
diff --git a/page.go b/page.go
index 3f1e6b3..fe639fa 100644
--- a/page.go
+++ b/page.go
@@ -17,6 +17,26 @@ const (
 	KeepPage     = 0x8000 /**< leave this page alone during spill */
 )
 
+// maxCommitPages is the maximum number of pages to commit in one writev() call.
+const maxCommitPages 64
+
+/* max bytes to write in one call */
+const maxWriteByteCount 0x80000000U    // TODO: #define MAX_WRITE 0x80000000U >> (sizeof(ssize_t) == 4))
+
+// TODO:
+// #if defined(IOV_MAX) && IOV_MAX < MDB_COMMIT_PAGES
+// #undef MDB_COMMIT_PAGES
+// #define MDB_COMMIT_PAGES	IOV_MAX
+// #endif
+
+// TODO: #define MDB_PS_MODIFY	1
+// TODO: #define MDB_PS_ROOTONLY	2
+// TODO: #define MDB_PS_FIRST	4
+// TODO: #define MDB_PS_LAST		8
+
+// TODO: #define MDB_SPLIT_REPLACE	MDB_APPENDDUP	/**< newkey is not new */
+
+
 type page struct {
 	header struct {
 		id                int
@@ -28,6 +48,11 @@ type page struct {
 	metadata []byte
 }
 
+type pageState struct {
+	head int  /**< Reclaimed freeDB pages, or NULL before use */
+	last int  /**< ID of last used record, or 0 if !mf_pghead */
+}
+
 // nodeCount returns the number of nodes on the page.
 func (p *page) nodeCount() int {
 	return 0 // (p.header.lower - unsafe.Sizeof(p.header) >> 1
@@ -42,3 +67,4 @@ func (p *page) remainingSize() int {
 func (p *page) remainingSize() int {
 	return p.header.upper - p.header.lower
 }
+
diff --git a/transaction.go b/transaction.go
index 74118d1..1064e8e 100644
--- a/transaction.go
+++ b/transaction.go
@@ -31,3 +31,1509 @@ type transaction struct {
 	// Implicit from slices? TODO: MDB_dbi mt_numdbs;
 	mt_dirty_room int
 }
+
+// ntxn represents a nested transaction.
+type ntxn struct {
+	transaction *transaction /**< the transaction */
+	pageState pageState /**< parent transaction's saved freestate */
+}
+
+
+func (t *transaction) allocPage(num int) *page {
+	/*
+	MDB_env *env = txn->mt_env;
+	MDB_page *ret = env->me_dpages;
+	size_t psize = env->me_psize, sz = psize, off;
+	// For ! #MDB_NOMEMINIT, psize counts how much to init.
+	// For a single page alloc, we init everything after the page header.
+	// For multi-page, we init the final page; if the caller needed that
+	// many pages they will be filling in at least up to the last page.
+	if (num == 1) {
+		if (ret) {
+			VGMEMP_ALLOC(env, ret, sz);
+			VGMEMP_DEFINED(ret, sizeof(ret->mp_next));
+			env->me_dpages = ret->mp_next;
+			return ret;
+		}
+		psize -= off = PAGEHDRSZ;
+	} else {
+		sz *= num;
+		off = sz - psize;
+	}
+	if ((ret = malloc(sz)) != NULL) {
+		VGMEMP_ALLOC(env, ret, sz);
+		if (!(env->me_flags & MDB_NOMEMINIT)) {
+			memset((char *)ret + off, 0, psize);
+			ret->mp_pad = 0;
+		}
+	} else {
+		txn->mt_flags |= MDB_TXN_ERROR;
+	}
+	return ret;
+	*/
+	return nil
+}
+
+// Find oldest txnid still referenced. Expects txn->mt_txnid > 0.
+func (t *transaction) oldest() int {
+	/*
+	int i;
+	txnid_t mr, oldest = txn->mt_txnid - 1;
+	if (txn->mt_env->me_txns) {
+		MDB_reader *r = txn->mt_env->me_txns->mti_readers;
+		for (i = txn->mt_env->me_txns->mti_numreaders; --i >= 0; ) {
+			if (r[i].mr_pid) {
+				mr = r[i].mr_txnid;
+				if (oldest > mr)
+					oldest = mr;
+			}
+		}
+	}
+	return oldest;
+	*/
+	return 0
+}
+
+// Add a page to the txn's dirty list
+func (t *transaction) dirty(p *page) {
+	/*
+	MDB_ID2 mid;
+	int rc, (*insert)(MDB_ID2L, MDB_ID2 *);
+
+	if (txn->mt_env->me_flags & MDB_WRITEMAP) {
+		insert = mdb_mid2l_append;
+	} else {
+		insert = mdb_mid2l_insert;
+	}
+	mid.mid = mp->mp_pgno;
+	mid.mptr = mp;
+	rc = insert(txn->mt_u.dirty_list, &mid);
+	mdb_tassert(txn, rc == 0);
+	txn->mt_dirty_room--;
+	*/
+}
+
+// Pull a page off the txn's spill list, if present.
+// If a page being referenced was spilled to disk in this txn, bring
+// it back and make it dirty/writable again.
+// @param[in] txn the transaction handle.
+// @param[in] mp the page being referenced. It must not be dirty.
+// @param[out] ret the writable page, if any. ret is unchanged if
+// mp wasn't spilled.
+func (t *transaction) unspill(p *page) *page {
+	/*
+	MDB_env *env = txn->mt_env;
+	const MDB_txn *tx2;
+	unsigned x;
+	pgno_t pgno = mp->mp_pgno, pn = pgno << 1;
+
+	for (tx2 = txn; tx2; tx2=tx2->mt_parent) {
+		if (!tx2->mt_spill_pgs)
+			continue;
+		x = mdb_midl_search(tx2->mt_spill_pgs, pn);
+		if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
+			MDB_page *np;
+			int num;
+			if (txn->mt_dirty_room == 0)
+				return MDB_TXN_FULL;
+			if (IS_OVERFLOW(mp))
+				num = mp->mp_pages;
+			else
+				num = 1;
+			if (env->me_flags & MDB_WRITEMAP) {
+				np = mp;
+			} else {
+				np = mdb_page_malloc(txn, num);
+				if (!np)
+					return ENOMEM;
+				if (num > 1)
+					memcpy(np, mp, num * env->me_psize);
+				else
+					mdb_page_copy(np, mp, env->me_psize);
+			}
+			if (tx2 == txn) {
+				// If in current txn, this page is no longer spilled.
+				// If it happens to be the last page, truncate the spill list.
+				// Otherwise mark it as deleted by setting the LSB.
+				if (x == txn->mt_spill_pgs[0])
+					txn->mt_spill_pgs[0]--;
+				else
+					txn->mt_spill_pgs[x] |= 1;
+			}	// otherwise, if belonging to a parent txn, the
+				// page remains spilled until child commits
+
+			mdb_page_dirty(txn, np);
+			np->mp_flags |= P_DIRTY;
+			*ret = np;
+			break;
+		}
+	}
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Back up parent txn's cursors, then grab the originals for tracking
+func (t *transaction) shadow(dst *transaction) error {
+	/*
+	MDB_cursor *mc, *bk;
+	MDB_xcursor *mx;
+	size_t size;
+	int i;
+
+	for (i = src->mt_numdbs; --i >= 0; ) {
+		if ((mc = src->mt_cursors[i]) != NULL) {
+			size = sizeof(MDB_cursor);
+			if (mc->mc_xcursor)
+				size += sizeof(MDB_xcursor);
+			for (; mc; mc = bk->mc_next) {
+				bk = malloc(size);
+				if (!bk)
+					return ENOMEM;
+				*bk = *mc;
+				mc->mc_backup = bk;
+				mc->mc_db = &dst->mt_dbs[i];
+				// Kill pointers into src - and dst to reduce abuse: The
+				// user may not use mc until dst ends. Otherwise we'd...
+				mc->mc_txn    = NULL;	// ...set this to dst
+				mc->mc_dbflag = NULL;	// ...and &dst->mt_dbflags[i]
+				if ((mx = mc->mc_xcursor) != NULL) {
+					*(MDB_xcursor *)(bk+1) = *mx;
+					mx->mx_cursor.mc_txn = NULL; // ...and dst.
+				}
+				mc->mc_next = dst->mt_cursors[i];
+				dst->mt_cursors[i] = mc;
+			}
+		}
+	}
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Close this write txn's cursors, give parent txn's cursors back to parent.
+// @param[in] txn the transaction handle.
+// @param[in] merge true to keep changes to parent cursors, false to revert.
+// @return 0 on success, non-zero on failure.
+func (t *transaction) closeCursors(merge bool) {
+	/*
+	MDB_cursor **cursors = txn->mt_cursors, *mc, *next, *bk;
+	MDB_xcursor *mx;
+	int i;
+
+	for (i = txn->mt_numdbs; --i >= 0; ) {
+		for (mc = cursors[i]; mc; mc = next) {
+			next = mc->mc_next;
+			if ((bk = mc->mc_backup) != NULL) {
+				if (merge) {
+					// Commit changes to parent txn
+					mc->mc_next = bk->mc_next;
+					mc->mc_backup = bk->mc_backup;
+					mc->mc_txn = bk->mc_txn;
+					mc->mc_db = bk->mc_db;
+					mc->mc_dbflag = bk->mc_dbflag;
+					if ((mx = mc->mc_xcursor) != NULL)
+						mx->mx_cursor.mc_txn = bk->mc_txn;
+				} else {
+					// Abort nested txn
+					*mc = *bk;
+					if ((mx = mc->mc_xcursor) != NULL)
+						*mx = *(MDB_xcursor *)(bk+1);
+				}
+				mc = bk;
+			}
+			// Only malloced cursors are permanently tracked.
+			free(mc);
+		}
+		cursors[i] = NULL;
+	}
+	*/
+}
+
+// Common code for #mdb_txn_begin() and #mdb_txn_renew().
+// @param[in] txn the transaction handle to initialize
+// @return 0 on success, non-zero on failure.
+func (t *transaction) renew() error {
+	/*
+	MDB_env *env = txn->mt_env;
+	MDB_txninfo *ti = env->me_txns;
+	MDB_meta *meta;
+	unsigned int i, nr;
+	uint16_t x;
+	int rc, new_notls = 0;
+
+	// Setup db info 
+	txn->mt_numdbs = env->me_numdbs;
+	txn->mt_dbxs = env->me_dbxs;	// mostly static anyway 
+
+	if (txn->mt_flags & MDB_TXN_RDONLY) {
+		if (!ti) {
+			meta = env->me_metas[ mdb_env_pick_meta(env) ];
+			txn->mt_txnid = meta->mm_txnid;
+			txn->mt_u.reader = NULL;
+		} else {
+			MDB_reader *r = (env->me_flags & MDB_NOTLS) ? txn->mt_u.reader :
+				pthread_getspecific(env->me_txkey);
+			if (r) {
+				if (r->mr_pid != env->me_pid || r->mr_txnid != (txnid_t)-1)
+					return MDB_BAD_RSLOT;
+			} else {
+				MDB_PID_T pid = env->me_pid;
+				pthread_t tid = pthread_self();
+
+				if (!(env->me_flags & MDB_LIVE_READER)) {
+					rc = mdb_reader_pid(env, Pidset, pid);
+					if (rc)
+						return rc;
+					env->me_flags |= MDB_LIVE_READER;
+				}
+
+				LOCK_MUTEX_R(env);
+				nr = ti->mti_numreaders;
+				for (i=0; i<nr; i++)
+					if (ti->mti_readers[i].mr_pid == 0)
+						break;
+				if (i == env->me_maxreaders) {
+					UNLOCK_MUTEX_R(env);
+					return MDB_READERS_FULL;
+				}
+				ti->mti_readers[i].mr_pid = pid;
+				ti->mti_readers[i].mr_tid = tid;
+				if (i == nr)
+					ti->mti_numreaders = ++nr;
+				// Save numreaders for un-mutexed mdb_env_close() 
+				env->me_numreaders = nr;
+				UNLOCK_MUTEX_R(env);
+
+				r = &ti->mti_readers[i];
+				new_notls = (env->me_flags & MDB_NOTLS);
+				if (!new_notls && (rc=pthread_setspecific(env->me_txkey, r))) {
+					r->mr_pid = 0;
+					return rc;
+				}
+			}
+			txn->mt_txnid = r->mr_txnid = ti->mti_txnid;
+			txn->mt_u.reader = r;
+			meta = env->me_metas[txn->mt_txnid & 1];
+		}
+	} else {
+		if (ti) {
+			LOCK_MUTEX_W(env);
+
+			txn->mt_txnid = ti->mti_txnid;
+			meta = env->me_metas[txn->mt_txnid & 1];
+		} else {
+			meta = env->me_metas[ mdb_env_pick_meta(env) ];
+			txn->mt_txnid = meta->mm_txnid;
+		}
+		txn->mt_txnid++;
+#if MDB_DEBUG
+		if (txn->mt_txnid == mdb_debug_start)
+			mdb_debug = 1;
+#endif
+		txn->mt_dirty_room = MDB_IDL_UM_MAX;
+		txn->mt_u.dirty_list = env->me_dirty_list;
+		txn->mt_u.dirty_list[0].mid = 0;
+		txn->mt_free_pgs = env->me_free_pgs;
+		txn->mt_free_pgs[0] = 0;
+		txn->mt_spill_pgs = NULL;
+		env->me_txn = txn;
+	}
+
+	// Copy the DB info and flags 
+	memcpy(txn->mt_dbs, meta->mm_dbs, 2 * sizeof(MDB_db));
+
+	// Moved to here to avoid a data race in read TXNs 
+	txn->mt_next_pgno = meta->mm_last_pg+1;
+
+	for (i=2; i<txn->mt_numdbs; i++) {
+		x = env->me_dbflags[i];
+		txn->mt_dbs[i].md_flags = x & PERSISTENT_FLAGS;
+		txn->mt_dbflags[i] = (x & MDB_VALID) ? DB_VALID|DB_STALE : 0;
+	}
+	txn->mt_dbflags[0] = txn->mt_dbflags[1] = DB_VALID;
+
+	if (env->me_maxpg < txn->mt_next_pgno) {
+		mdb_txn_reset0(txn, "renew0-mapfail");
+		if (new_notls) {
+			txn->mt_u.reader->mr_pid = 0;
+			txn->mt_u.reader = NULL;
+		}
+		return MDB_MAP_RESIZED;
+	}
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (t *transaction) Renew() error {
+	/*
+	int rc;
+
+	if (!txn || txn->mt_dbxs)	// A reset txn has mt_dbxs==NULL
+		return EINVAL;
+
+	if (txn->mt_env->me_flags & MDB_FATAL_ERROR) {
+		DPUTS("environment had fatal error, must shutdown!");
+		return MDB_PANIC;
+	}
+
+	rc = mdb_txn_renew0(txn);
+	if (rc == MDB_SUCCESS) {
+		DPRINTF(("renew txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+			txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
+			(void *)txn, (void *)txn->mt_env, txn->mt_dbs[MAIN_DBI].md_root));
+	}
+	return rc;
+	*/
+	return nil
+}
+
+func (t *transaction) DB() DB {
+	return t.db
+}
+
+// Export or close DBI handles opened in this txn.
+func (t *transaction) updateBuckets(keep bool) {
+	/*
+	int i;
+	MDB_dbi n = txn->mt_numdbs;
+	MDB_env *env = txn->mt_env;
+	unsigned char *tdbflags = txn->mt_dbflags;
+
+	for (i = n; --i >= 2;) {
+		if (tdbflags[i] & DB_NEW) {
+			if (keep) {
+				env->me_dbflags[i] = txn->mt_dbs[i].md_flags | MDB_VALID;
+			} else {
+				char *ptr = env->me_dbxs[i].md_name.mv_data;
+				env->me_dbxs[i].md_name.mv_data = NULL;
+				env->me_dbxs[i].md_name.mv_size = 0;
+				env->me_dbflags[i] = 0;
+				free(ptr);
+			}
+		}
+	}
+	if (keep && env->me_numdbs < n)
+		env->me_numdbs = n;
+	*/
+}
+
+// Common code for #mdb_txn_reset() and #mdb_txn_abort().
+// May be called twice for readonly txns: First reset it, then abort.
+// @param[in] txn the transaction handle to reset
+// @param[in] act why the transaction is being reset
+func (t *transaction) reset(act string) {
+	/*
+	MDB_env	*env = txn->mt_env;
+
+	// Close any DBI handles opened in this txn
+	mdb_dbis_update(txn, 0);
+
+	DPRINTF(("%s txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+		act, txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
+		(void *) txn, (void *)env, txn->mt_dbs[MAIN_DBI].md_root));
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
+		if (txn->mt_u.reader) {
+			txn->mt_u.reader->mr_txnid = (txnid_t)-1;
+			if (!(env->me_flags & MDB_NOTLS))
+				txn->mt_u.reader = NULL; // txn does not own reader
+		}
+		txn->mt_numdbs = 0;		// close nothing if called again
+		txn->mt_dbxs = NULL;	// mark txn as reset
+	} else {
+		mdb_cursors_close(txn, 0);
+
+		if (!(env->me_flags & MDB_WRITEMAP)) {
+			mdb_dlist_free(txn);
+		}
+		mdb_midl_free(env->me_pghead);
+
+		if (txn->mt_parent) {
+			txn->mt_parent->mt_child = NULL;
+			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
+			mdb_midl_free(txn->mt_free_pgs);
+			mdb_midl_free(txn->mt_spill_pgs);
+			free(txn->mt_u.dirty_list);
+			return;
+		}
+
+		if (mdb_midl_shrink(&txn->mt_free_pgs))
+			env->me_free_pgs = txn->mt_free_pgs;
+		env->me_pghead = NULL;
+		env->me_pglast = 0;
+
+		env->me_txn = NULL;
+		// The writer mutex was locked in mdb_txn_begin.
+		if (env->me_txns)
+			UNLOCK_MUTEX_W(env);
+	}
+	*/
+}
+
+func (t *transaction) Reset() {
+	/*
+	if (txn == NULL)
+		return;
+
+	// This call is only valid for read-only txns
+	if (!(txn->mt_flags & MDB_TXN_RDONLY))
+		return;
+
+	mdb_txn_reset0(txn, "reset");
+	*/
+}
+
+func (t *transaction) Abort() {
+	/*
+	if (txn == NULL)
+		return;
+
+	if (txn->mt_child)
+		mdb_txn_abort(txn->mt_child);
+
+	mdb_txn_reset0(txn, "abort");
+	// Free reader slot tied to this txn (if MDB_NOTLS && writable FS)
+	if ((txn->mt_flags & MDB_TXN_RDONLY) && txn->mt_u.reader)
+		txn->mt_u.reader->mr_pid = 0;
+
+	free(txn);
+	*/
+}
+
+// Save the freelist as of this transaction to the freeDB.
+// This changes the freelist. Keep trying until it stabilizes.
+func (t *transaction) saveFreelist() error {
+	/*
+	// env->me_pghead[] can grow and shrink during this call.
+	// env->me_pglast and txn->mt_free_pgs[] can only grow.
+	// Page numbers cannot disappear from txn->mt_free_pgs[].
+	MDB_cursor mc;
+	MDB_env	*env = txn->mt_env;
+	int rc, maxfree_1pg = env->me_maxfree_1pg, more = 1;
+	txnid_t	pglast = 0, head_id = 0;
+	pgno_t	freecnt = 0, *free_pgs, *mop;
+	ssize_t	head_room = 0, total_room = 0, mop_len, clean_limit;
+
+	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
+
+	if (env->me_pghead) {
+		// Make sure first page of freeDB is touched and on freelist 
+		rc = mdb_page_search(&mc, NULL, MDB_PS_FIRST|MDB_PS_MODIFY);
+		if (rc && rc != MDB_NOTFOUND)
+			return rc;
+	}
+
+	// MDB_RESERVE cancels meminit in ovpage malloc (when no WRITEMAP)
+	clean_limit = (env->me_flags & (MDB_NOMEMINIT|MDB_WRITEMAP))
+		? SSIZE_MAX : maxfree_1pg;
+
+	for (;;) {
+		// Come back here after each Put() in case freelist changed
+		MDB_val key, data;
+		pgno_t *pgs;
+		ssize_t j;
+
+		// If using records from freeDB which we have not yet
+		// deleted, delete them and any we reserved for me_pghead.
+		while (pglast < env->me_pglast) {
+			rc = mdb_cursor_first(&mc, &key, NULL);
+			if (rc)
+				return rc;
+			pglast = head_id = *(txnid_t *)key.mv_data;
+			total_room = head_room = 0;
+			mdb_tassert(txn, pglast <= env->me_pglast);
+			rc = mdb_cursor_del(&mc, 0);
+			if (rc)
+				return rc;
+		}
+
+		// Save the IDL of pages freed by this txn, to a single record
+		if (freecnt < txn->mt_free_pgs[0]) {
+			if (!freecnt) {
+				// Make sure last page of freeDB is touched and on freelist
+				rc = mdb_page_search(&mc, NULL, MDB_PS_LAST|MDB_PS_MODIFY);
+				if (rc && rc != MDB_NOTFOUND)
+					return rc;
+			}
+			free_pgs = txn->mt_free_pgs;
+			// Write to last page of freeDB
+			key.mv_size = sizeof(txn->mt_txnid);
+			key.mv_data = &txn->mt_txnid;
+			do {
+				freecnt = free_pgs[0];
+				data.mv_size = MDB_IDL_SIZEOF(free_pgs);
+				rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
+				if (rc)
+					return rc;
+				// Retry if mt_free_pgs[] grew during the Put()
+				free_pgs = txn->mt_free_pgs;
+			} while (freecnt < free_pgs[0]);
+			mdb_midl_sort(free_pgs);
+			memcpy(data.mv_data, free_pgs, data.mv_size);
+#if (MDB_DEBUG) > 1
+			{
+				unsigned int i = free_pgs[0];
+				DPRINTF(("IDL write txn %"Z"u root %"Z"u num %u",
+					txn->mt_txnid, txn->mt_dbs[FREE_DBI].md_root, i));
+				for (; i; i--)
+					DPRINTF(("IDL %"Z"u", free_pgs[i]));
+			}
+#endif
+			continue;
+		}
+
+		mop = env->me_pghead;
+		mop_len = mop ? mop[0] : 0;
+
+		// Reserve records for me_pghead[]. Split it if multi-page,
+		// to avoid searching freeDB for a page range. Use keys in
+		// range [1,me_pglast]: Smaller than txnid of oldest reader.
+		if (total_room >= mop_len) {
+			if (total_room == mop_len || --more < 0)
+				break;
+		} else if (head_room >= maxfree_1pg && head_id > 1) {
+			// Keep current record (overflow page), add a new one
+			head_id--;
+			head_room = 0;
+		}
+		// (Re)write {key = head_id, IDL length = head_room}
+		total_room -= head_room;
+		head_room = mop_len - total_room;
+		if (head_room > maxfree_1pg && head_id > 1) {
+			// Overflow multi-page for part of me_pghead
+			head_room /= head_id; // amortize page sizes
+			head_room += maxfree_1pg - head_room % (maxfree_1pg + 1);
+		} else if (head_room < 0) {
+			// Rare case, not bothering to delete this record
+			head_room = 0;
+		}
+		key.mv_size = sizeof(head_id);
+		key.mv_data = &head_id;
+		data.mv_size = (head_room + 1) * sizeof(pgno_t);
+		rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
+		if (rc)
+			return rc;
+		// IDL is initially empty, zero out at least the length 
+		pgs = (pgno_t *)data.mv_data;
+		j = head_room > clean_limit ? head_room : 0;
+		do {
+			pgs[j] = 0;
+		} while (--j >= 0);
+		total_room += head_room;
+	}
+
+	// Fill in the reserved me_pghead records
+	rc = MDB_SUCCESS;
+	if (mop_len) {
+		MDB_val key, data;
+
+		mop += mop_len;
+		rc = mdb_cursor_first(&mc, &key, &data);
+		for (; !rc; rc = mdb_cursor_next(&mc, &key, &data, MDB_NEXT)) {
+			unsigned flags = MDB_CURRENT;
+			txnid_t id = *(txnid_t *)key.mv_data;
+			ssize_t	len = (ssize_t)(data.mv_size / sizeof(MDB_ID)) - 1;
+			MDB_ID save;
+
+			mdb_tassert(txn, len >= 0 && id <= env->me_pglast);
+			key.mv_data = &id;
+			if (len > mop_len) {
+				len = mop_len;
+				data.mv_size = (len + 1) * sizeof(MDB_ID);
+				flags = 0;
+			}
+			data.mv_data = mop -= len;
+			save = mop[0];
+			mop[0] = len;
+			rc = mdb_cursor_put(&mc, &key, &data, flags);
+			mop[0] = save;
+			if (rc || !(mop_len -= len))
+				break;
+		}
+	}
+	return rc;
+	*/
+	return nil
+}
+
+// Flush (some) dirty pages to the map, after clearing their dirty flag.
+// @param[in] txn the transaction that's being committed
+// @param[in] keep number of initial pages in dirty_list to keep dirty.
+// @return 0 on success, non-zero on failure.
+func (t *transaction) flush(keep bool) {
+	/*
+	MDB_env		*env = txn->mt_env;
+	MDB_ID2L	dl = txn->mt_u.dirty_list;
+	unsigned	psize = env->me_psize, j;
+	int			i, pagecount = dl[0].mid, rc;
+	size_t		size = 0, pos = 0;
+	pgno_t		pgno = 0;
+	MDB_page	*dp = NULL;
+#ifdef _WIN32
+	OVERLAPPED	ov;
+#else
+	struct iovec iov[MDB_COMMIT_PAGES];
+	ssize_t		wpos = 0, wsize = 0, wres;
+	size_t		next_pos = 1; // impossible pos, so pos != next_pos
+	int			n = 0;
+#endif
+
+	j = i = keep;
+
+	if (env->me_flags & MDB_WRITEMAP) {
+		// Clear dirty flags 
+		while (++i <= pagecount) {
+			dp = dl[i].mptr;
+			// Don't flush this page yet 
+			if (dp->mp_flags & P_KEEP) {
+				dp->mp_flags ^= P_KEEP;
+				dl[++j] = dl[i];
+				continue;
+			}
+			dp->mp_flags &= ~P_DIRTY;
+		}
+		goto done;
+	}
+
+	// Write the pages
+	for (;;) {
+		if (++i <= pagecount) {
+			dp = dl[i].mptr;
+			// Don't flush this page yet
+			if (dp->mp_flags & P_KEEP) {
+				dp->mp_flags ^= P_KEEP;
+				dl[i].mid = 0;
+				continue;
+			}
+			pgno = dl[i].mid;
+			// clear dirty flag
+			dp->mp_flags &= ~P_DIRTY;
+			pos = pgno * psize;
+			size = psize;
+			if (IS_OVERFLOW(dp)) size *= dp->mp_pages;
+		}
+#ifdef _WIN32
+		else break;
+
+		// Windows actually supports scatter/gather I/O, but only on
+		// unbuffered file handles. Since we're relying on the OS page
+		// cache for all our data, that's self-defeating. So we just
+		// write pages one at a time. We use the ov structure to set
+		// the write offset, to at least save the overhead of a Seek
+		// system call.
+		DPRINTF(("committing page %"Z"u", pgno));
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = pos & 0xffffffff;
+		ov.OffsetHigh = pos >> 16 >> 16;
+		if (!WriteFile(env->me_fd, dp, size, NULL, &ov)) {
+			rc = ErrCode();
+			DPRINTF(("WriteFile: %d", rc));
+			return rc;
+		}
+#else
+		// Write up to MDB_COMMIT_PAGES dirty pages at a time.
+		if (pos!=next_pos || n==MDB_COMMIT_PAGES || wsize+size>MAX_WRITE) {
+			if (n) {
+				// Write previous page(s)
+#ifdef MDB_USE_PWRITEV
+				wres = pwritev(env->me_fd, iov, n, wpos);
+#else
+				if (n == 1) {
+					wres = pwrite(env->me_fd, iov[0].iov_base, wsize, wpos);
+				} else {
+					if (lseek(env->me_fd, wpos, SEEK_SET) == -1) {
+						rc = ErrCode();
+						DPRINTF(("lseek: %s", strerror(rc)));
+						return rc;
+					}
+					wres = writev(env->me_fd, iov, n);
+				}
+#endif
+				if (wres != wsize) {
+					if (wres < 0) {
+						rc = ErrCode();
+						DPRINTF(("Write error: %s", strerror(rc)));
+					} else {
+						rc = EIO; // TODO: Use which error code?
+						DPUTS("short write, filesystem full?");
+					}
+					return rc;
+				}
+				n = 0;
+			}
+			if (i > pagecount)
+				break;
+			wpos = pos;
+			wsize = 0;
+		}
+		DPRINTF(("committing page %"Z"u", pgno));
+		next_pos = pos + size;
+		iov[n].iov_len = size;
+		iov[n].iov_base = (char *)dp;
+		wsize += size;
+		n++;
+#endif	// _WIN32
+	}
+
+	for (i = keep; ++i <= pagecount; ) {
+		dp = dl[i].mptr;
+		// This is a page we skipped above
+		if (!dl[i].mid) {
+			dl[++j] = dl[i];
+			dl[j].mid = dp->mp_pgno;
+			continue;
+		}
+		mdb_dpage_free(env, dp);
+	}
+
+done:
+	i--;
+	txn->mt_dirty_room += i - j;
+	dl[0].mid = j;
+	return MDB_SUCCESS;
+}
+
+int
+mdb_txn_commit(MDB_txn *txn)
+{
+	int		rc;
+	unsigned int i;
+	MDB_env	*env;
+
+	if (txn == NULL || txn->mt_env == NULL)
+		return EINVAL;
+
+	if (txn->mt_child) {
+		rc = mdb_txn_commit(txn->mt_child);
+		txn->mt_child = NULL;
+		if (rc)
+			goto fail;
+	}
+
+	env = txn->mt_env;
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
+		mdb_dbis_update(txn, 1);
+		txn->mt_numdbs = 2; // so txn_abort() doesn't close any new handles
+		mdb_txn_abort(txn);
+		return MDB_SUCCESS;
+	}
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_ERROR)) {
+		DPUTS("error flag is set, can't commit");
+		if (txn->mt_parent)
+			txn->mt_parent->mt_flags |= MDB_TXN_ERROR;
+		rc = MDB_BAD_TXN;
+		goto fail;
+	}
+
+	if (txn->mt_parent) {
+		MDB_txn *parent = txn->mt_parent;
+		MDB_ID2L dst, src;
+		MDB_IDL pspill;
+		unsigned x, y, len, ps_len;
+
+		// Append our free list to parent's
+		rc = mdb_midl_append_list(&parent->mt_free_pgs, txn->mt_free_pgs);
+		if (rc)
+			goto fail;
+		mdb_midl_free(txn->mt_free_pgs);
+		// Failures after this must either undo the changes
+		// to the parent or set MDB_TXN_ERROR in the parent.
+
+		parent->mt_next_pgno = txn->mt_next_pgno;
+		parent->mt_flags = txn->mt_flags;
+
+		// Merge our cursors into parent's and close them
+		mdb_cursors_close(txn, 1);
+
+		// Update parent's DB table.
+		memcpy(parent->mt_dbs, txn->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
+		parent->mt_numdbs = txn->mt_numdbs;
+		parent->mt_dbflags[0] = txn->mt_dbflags[0];
+		parent->mt_dbflags[1] = txn->mt_dbflags[1];
+		for (i=2; i<txn->mt_numdbs; i++) {
+			// preserve parent's DB_NEW status
+			x = parent->mt_dbflags[i] & DB_NEW;
+			parent->mt_dbflags[i] = txn->mt_dbflags[i] | x;
+		}
+
+		dst = parent->mt_u.dirty_list;
+		src = txn->mt_u.dirty_list;
+		// Remove anything in our dirty list from parent's spill list
+		if ((pspill = parent->mt_spill_pgs) && (ps_len = pspill[0])) {
+			x = y = ps_len;
+			pspill[0] = (pgno_t)-1;
+			// Mark our dirty pages as deleted in parent spill list 
+			for (i=0, len=src[0].mid; ++i <= len; ) {
+				MDB_ID pn = src[i].mid << 1;
+				while (pn > pspill[x])
+					x--;
+				if (pn == pspill[x]) {
+					pspill[x] = 1;
+					y = --x;
+				}
+			}
+			// Squash deleted pagenums if we deleted any
+			for (x=y; ++x <= ps_len; )
+				if (!(pspill[x] & 1))
+					pspill[++y] = pspill[x];
+			pspill[0] = y;
+		}
+
+		// Find len = length of merging our dirty list with parent's
+		x = dst[0].mid;
+		dst[0].mid = 0;		// simplify loops
+		if (parent->mt_parent) {
+			len = x + src[0].mid;
+			y = mdb_mid2l_search(src, dst[x].mid + 1) - 1;
+			for (i = x; y && i; y--) {
+				pgno_t yp = src[y].mid;
+				while (yp < dst[i].mid)
+					i--;
+				if (yp == dst[i].mid) {
+					i--;
+					len--;
+				}
+			}
+		} else { // Simplify the above for single-ancestor case
+			len = MDB_IDL_UM_MAX - txn->mt_dirty_room;
+		}
+		// Merge our dirty list with parent's 
+		y = src[0].mid;
+		for (i = len; y; dst[i--] = src[y--]) {
+			pgno_t yp = src[y].mid;
+			while (yp < dst[x].mid)
+				dst[i--] = dst[x--];
+			if (yp == dst[x].mid)
+				free(dst[x--].mptr);
+		}
+		mdb_tassert(txn, i == x);
+		dst[0].mid = len;
+		free(txn->mt_u.dirty_list);
+		parent->mt_dirty_room = txn->mt_dirty_room;
+		if (txn->mt_spill_pgs) {
+			if (parent->mt_spill_pgs) {
+				// TODO: Prevent failure here, so parent does not fail 
+				rc = mdb_midl_append_list(&parent->mt_spill_pgs, txn->mt_spill_pgs);
+				if (rc)
+					parent->mt_flags |= MDB_TXN_ERROR;
+				mdb_midl_free(txn->mt_spill_pgs);
+				mdb_midl_sort(parent->mt_spill_pgs);
+			} else {
+				parent->mt_spill_pgs = txn->mt_spill_pgs;
+			}
+		}
+
+		parent->mt_child = NULL;
+		mdb_midl_free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pghead);
+		free(txn);
+		return rc;
+	}
+
+	if (txn != env->me_txn) {
+		DPUTS("attempt to commit unknown transaction");
+		rc = EINVAL;
+		goto fail;
+	}
+
+	mdb_cursors_close(txn, 0);
+
+	if (!txn->mt_u.dirty_list[0].mid &&
+		!(txn->mt_flags & (MDB_TXN_DIRTY|MDB_TXN_SPILLS)))
+		goto done;
+
+	DPRINTF(("committing txn %"Z"u %p on mdbenv %p, root page %"Z"u",
+	    txn->mt_txnid, (void*)txn, (void*)env, txn->mt_dbs[MAIN_DBI].md_root));
+
+	// Update DB root pointers
+	if (txn->mt_numdbs > 2) {
+		MDB_cursor mc;
+		MDB_dbi i;
+		MDB_val data;
+		data.mv_size = sizeof(MDB_db);
+
+		mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
+		for (i = 2; i < txn->mt_numdbs; i++) {
+			if (txn->mt_dbflags[i] & DB_DIRTY) {
+				data.mv_data = &txn->mt_dbs[i];
+				rc = mdb_cursor_put(&mc, &txn->mt_dbxs[i].md_name, &data, 0);
+				if (rc)
+					goto fail;
+			}
+		}
+	}
+
+	rc = mdb_freelist_save(txn);
+	if (rc)
+		goto fail;
+
+	mdb_midl_free(env->me_pghead);
+	env->me_pghead = NULL;
+	if (mdb_midl_shrink(&txn->mt_free_pgs))
+		env->me_free_pgs = txn->mt_free_pgs;
+
+#if (MDB_DEBUG) > 2
+	mdb_audit(txn);
+#endif
+
+	if ((rc = mdb_page_flush(txn, 0)) ||
+		(rc = mdb_env_sync(env, 0)) ||
+		(rc = mdb_env_write_meta(txn)))
+		goto fail;
+
+done:
+	env->me_pglast = 0;
+	env->me_txn = NULL;
+	mdb_dbis_update(txn, 1);
+
+	if (env->me_txns)
+		UNLOCK_MUTEX_W(env);
+	free(txn);
+
+	return MDB_SUCCESS;
+
+fail:
+	mdb_txn_abort(txn);
+	return rc;
+	*/
+	return nil
+}
+
+// Update the environment info to commit a transaction.
+// @param[in] txn the transaction that's being committed
+// @return 0 on success, non-zero on failure.
+func (t *transaction) writeMeta() error {
+	/*
+	MDB_env *env;
+	MDB_meta	meta, metab, *mp;
+	off_t off;
+	int rc, len, toggle;
+	char *ptr;
+	HANDLE mfd;
+#ifdef _WIN32
+	OVERLAPPED ov;
+#else
+	int r2;
+#endif
+
+	toggle = txn->mt_txnid & 1;
+	DPRINTF(("writing meta page %d for root page %"Z"u",
+		toggle, txn->mt_dbs[MAIN_DBI].md_root));
+
+	env = txn->mt_env;
+	mp = env->me_metas[toggle];
+
+	if (env->me_flags & MDB_WRITEMAP) {
+		// Persist any increases of mapsize config
+		if (env->me_mapsize > mp->mm_mapsize)
+			mp->mm_mapsize = env->me_mapsize;
+		mp->mm_dbs[0] = txn->mt_dbs[0];
+		mp->mm_dbs[1] = txn->mt_dbs[1];
+		mp->mm_last_pg = txn->mt_next_pgno - 1;
+		mp->mm_txnid = txn->mt_txnid;
+		if (!(env->me_flags & (MDB_NOMETASYNC|MDB_NOSYNC))) {
+			unsigned meta_size = env->me_psize;
+			rc = (env->me_flags & MDB_MAPASYNC) ? MS_ASYNC : MS_SYNC;
+			ptr = env->me_map;
+			if (toggle) {
+#ifndef _WIN32	// POSIX msync() requires ptr = start of OS page
+				if (meta_size < env->me_os_psize)
+					meta_size += meta_size;
+				else
+#endif
+					ptr += meta_size;
+			}
+			if (MDB_MSYNC(ptr, meta_size, rc)) {
+				rc = ErrCode();
+				goto fail;
+			}
+		}
+		goto done;
+	}
+	metab.mm_txnid = env->me_metas[toggle]->mm_txnid;
+	metab.mm_last_pg = env->me_metas[toggle]->mm_last_pg;
+
+	ptr = (char *)&meta;
+	if (env->me_mapsize > mp->mm_mapsize) {
+		// Persist any increases of mapsize config
+		meta.mm_mapsize = env->me_mapsize;
+		off = offsetof(MDB_meta, mm_mapsize);
+	} else {
+		off = offsetof(MDB_meta, mm_dbs[0].md_depth);
+	}
+	len = sizeof(MDB_meta) - off;
+
+	ptr += off;
+	meta.mm_dbs[0] = txn->mt_dbs[0];
+	meta.mm_dbs[1] = txn->mt_dbs[1];
+	meta.mm_last_pg = txn->mt_next_pgno - 1;
+	meta.mm_txnid = txn->mt_txnid;
+
+	if (toggle)
+		off += env->me_psize;
+	off += PAGEHDRSZ;
+
+	// Write to the SYNC fd
+	mfd = env->me_flags & (MDB_NOSYNC|MDB_NOMETASYNC) ?
+		env->me_fd : env->me_mfd;
+#ifdef _WIN32
+	{
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		if (!WriteFile(mfd, ptr, len, (DWORD *)&rc, &ov))
+			rc = -1;
+	}
+#else
+	rc = pwrite(mfd, ptr, len, off);
+#endif
+	if (rc != len) {
+		rc = rc < 0 ? ErrCode() : EIO;
+		DPUTS("write failed, disk error?");
+		// On a failure, the pagecache still contains the new data.
+		// Write some old data back, to prevent it from being used.
+		// Use the non-SYNC fd; we know it will fail anyway.
+		meta.mm_last_pg = metab.mm_last_pg;
+		meta.mm_txnid = metab.mm_txnid;
+#ifdef _WIN32
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		WriteFile(env->me_fd, ptr, len, NULL, &ov);
+#else
+		r2 = pwrite(env->me_fd, ptr, len, off);
+		(void)r2;	// Silence warnings. We don't care about pwrite's return value
+#endif
+fail:
+		env->me_flags |= MDB_FATAL_ERROR;
+		return rc;
+	}
+done:
+	// Memory ordering issues are irrelevant; since the entire writer
+	// is wrapped by wmutex, all of these changes will become visible
+	// after the wmutex is unlocked. Since the DB is multi-version,
+	// readers will get consistent data regardless of how fresh or
+	// how stale their view of these values is.
+	if (env->me_txns)
+		env->me_txns->mti_txnid = txn->mt_txnid;
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+// Find the address of the page corresponding to a given page number.
+// @param[in] txn the transaction for this access.
+// @param[in] pgno the page number for the page to retrieve.
+// @param[out] ret address of a pointer where the page's address will be stored.
+// @param[out] lvl dirty_list inheritance level of found page. 1=current txn, 0=mapped page.
+// @return 0 on success, non-zero on failure.
+func (t *transaction) getPage(id int) (*page, int, error) {
+	/*
+	MDB_env *env = txn->mt_env;
+	MDB_page *p = NULL;
+	int level;
+
+	if (!((txn->mt_flags & MDB_TXN_RDONLY) | (env->me_flags & MDB_WRITEMAP))) {
+		MDB_txn *tx2 = txn;
+		level = 1;
+		do {
+			MDB_ID2L dl = tx2->mt_u.dirty_list;
+			unsigned x;
+			// Spilled pages were dirtied in this txn and flushed
+			// because the dirty list got full. Bring this page
+			// back in from the map (but don't unspill it here,
+			// leave that unless page_touch happens again).
+			if (tx2->mt_spill_pgs) {
+				MDB_ID pn = pgno << 1;
+				x = mdb_midl_search(tx2->mt_spill_pgs, pn);
+				if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
+					p = (MDB_page *)(env->me_map + env->me_psize * pgno);
+					goto done;
+				}
+			}
+			if (dl[0].mid) {
+				unsigned x = mdb_mid2l_search(dl, pgno);
+				if (x <= dl[0].mid && dl[x].mid == pgno) {
+					p = dl[x].mptr;
+					goto done;
+				}
+			}
+			level++;
+		} while ((tx2 = tx2->mt_parent) != NULL);
+	}
+
+	if (pgno < txn->mt_next_pgno) {
+		level = 0;
+		p = (MDB_page *)(env->me_map + env->me_psize * pgno);
+	} else {
+		DPRINTF(("page %"Z"u not found", pgno));
+		txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_PAGE_NOTFOUND;
+	}
+
+done:
+	*ret = p;
+	if (lvl)
+		*lvl = level;
+	return MDB_SUCCESS;
+	*/
+
+	return nil, 0, nil
+}
+
+// Return the data associated with a given node.
+// @param[in] txn The transaction for this operation.
+// @param[in] leaf The node being read.
+// @param[out] data Updated to point to the node's data.
+// @return 0 on success, non-zero on failure.
+func (t *transaction) readNode(leaf *node, data []byte) error {
+	/*
+	MDB_page	*omp;		// overflow page
+	pgno_t		 pgno;
+	int rc;
+
+	if (!F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+		data->mv_size = NODEDSZ(leaf);
+		data->mv_data = NODEDATA(leaf);
+		return MDB_SUCCESS;
+	}
+
+	// Read overflow data.
+	data->mv_size = NODEDSZ(leaf);
+	memcpy(&pgno, NODEDATA(leaf), sizeof(pgno));
+	if ((rc = mdb_page_get(txn, pgno, &omp, NULL)) != 0) {
+		DPRINTF(("read overflow page %"Z"u failed", pgno));
+		return rc;
+	}
+	data->mv_data = METADATA(omp);
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (t *transaction) Get(bucket Bucket, key []byte) ([]byte, error) {
+	/*
+	MDB_cursor	mc;
+	MDB_xcursor	mx;
+	int exact = 0;
+	DKBUF;
+
+	if (key == NULL || data == NULL)
+		return EINVAL;
+
+	DPRINTF(("===> get db %u key [%s]", dbi, DKEY(key)));
+
+	if (txn == NULL || !dbi || dbi >= txn->mt_numdbs || !(txn->mt_dbflags[dbi] & DB_VALID))
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_ERROR)
+		return MDB_BAD_TXN;
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+	return mdb_cursor_set(&mc, key, data, MDB_SET, &exact);
+	*/
+	return nil, nil
+}
+
+func (t *transaction) Cursor(b Bucket) (Cursor, error) {
+	/*
+	MDB_cursor	*mc;
+	size_t size = sizeof(MDB_cursor);
+
+	if (txn == NULL || ret == NULL || dbi >= txn->mt_numdbs || !(txn->mt_dbflags[dbi] & DB_VALID))
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_ERROR)
+		return MDB_BAD_TXN;
+
+	// Allow read access to the freelist
+	if (!dbi && !F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
+		return EINVAL;
+
+	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT)
+		size += sizeof(MDB_xcursor);
+
+	if ((mc = malloc(size)) != NULL) {
+		mdb_cursor_init(mc, txn, dbi, (MDB_xcursor *)(mc + 1));
+		if (txn->mt_cursors) {
+			mc->mc_next = txn->mt_cursors[dbi];
+			txn->mt_cursors[dbi] = mc;
+			mc->mc_flags |= C_UNTRACK;
+		}
+	} else {
+		return ENOMEM;
+	}
+
+	*ret = mc;
+
+	return MDB_SUCCESS;
+	*/
+	return nil
+}
+
+func (t *transaction) Renew(c Cursor) error {
+	/*
+	if (txn == NULL || mc == NULL || mc->mc_dbi >= txn->mt_numdbs)
+		return EINVAL;
+
+	if ((mc->mc_flags & C_UNTRACK) || txn->mt_cursors)
+		return EINVAL;
+
+	mdb_cursor_init(mc, txn, mc->mc_dbi, mc->mc_xcursor);
+	return MDB_SUCCESS;
+	*/
+}
+
+func (t *transaction) Delete(b *bucket, key []byte, data []byte) error {
+	/*
+	MDB_cursor mc;
+	MDB_xcursor mx;
+	MDB_cursor_op op;
+	MDB_val rdata, *xdata;
+	int		 rc, exact;
+	DKBUF;
+
+	if (key == NULL)
+		return EINVAL;
+
+	DPRINTF(("====> delete db %u key [%s]", dbi, DKEY(key)));
+
+	if (txn == NULL || !dbi || dbi >= txn->mt_numdbs || !(txn->mt_dbflags[dbi] & DB_VALID))
+		return EINVAL;
+
+	if (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_ERROR))
+		return (txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+
+	exact = 0;
+	if (!F_ISSET(txn->mt_dbs[dbi].md_flags, MDB_DUPSORT)) {
+		// must ignore any data
+		data = NULL;
+	}
+	if (data) {
+		op = MDB_GET_BOTH;
+		rdata = *data;
+		xdata = &rdata;
+	} else {
+		op = MDB_SET;
+		xdata = NULL;
+	}
+	rc = mdb_cursor_set(&mc, key, xdata, op, &exact);
+	if (rc == 0) {
+		// let mdb_page_split know about this cursor if needed:
+		// delete will trigger a rebalance; if it needs to move
+		// a node from one page to another, it will have to
+		// update the parent's separator key(s). If the new sepkey
+		// is larger than the current one, the parent page may
+		// run out of space, triggering a split. We need this
+		// cursor to be consistent until the end of the rebalance.
+		mc.mc_flags |= C_UNTRACK;
+		mc.mc_next = txn->mt_cursors[dbi];
+		txn->mt_cursors[dbi] = &mc;
+		rc = mdb_cursor_del(&mc, data ? 0 : MDB_NODUPDATA);
+		txn->mt_cursors[dbi] = mc.mc_next;
+	}
+	return rc;
+	*/
+	return nil
+}
+
+func (t *transaction) Put(b Bucket, key []byte, data []byte, flags int) error {
+	/*
+	MDB_cursor mc;
+	MDB_xcursor mx;
+
+	if (key == NULL || data == NULL)
+		return EINVAL;
+
+	if (txn == NULL || !dbi || dbi >= txn->mt_numdbs || !(txn->mt_dbflags[dbi] & DB_VALID))
+		return EINVAL;
+
+	if ((flags & (MDB_NOOVERWRITE|MDB_NODUPDATA|MDB_RESERVE|MDB_APPEND|MDB_APPENDDUP)) != flags)
+		return EINVAL;
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+	return mdb_cursor_put(&mc, key, data, flags);
+	*/
+}
+
+func (t *transaction) Bucket(name string, flags int) (Bucket, error) {
+	/*
+	MDB_val key, data;
+	MDB_dbi i;
+	MDB_cursor mc;
+	int rc, dbflag, exact;
+	unsigned int unused = 0;
+	size_t len;
+
+	if (txn->mt_dbxs[FREE_DBI].md_cmp == NULL) {
+		mdb_default_cmp(txn, FREE_DBI);
+	}
+
+	if ((flags & VALID_FLAGS) != flags)
+		return EINVAL;
+	if (txn->mt_flags & MDB_TXN_ERROR)
+		return MDB_BAD_TXN;
+
+	// main DB?
+	if (!name) {
+		*dbi = MAIN_DBI;
+		if (flags & PERSISTENT_FLAGS) {
+			uint16_t f2 = flags & PERSISTENT_FLAGS;
+			// make sure flag changes get committed
+			if ((txn->mt_dbs[MAIN_DBI].md_flags | f2) != txn->mt_dbs[MAIN_DBI].md_flags) {
+				txn->mt_dbs[MAIN_DBI].md_flags |= f2;
+				txn->mt_flags |= MDB_TXN_DIRTY;
+			}
+		}
+		mdb_default_cmp(txn, MAIN_DBI);
+		return MDB_SUCCESS;
+	}
+
+	if (txn->mt_dbxs[MAIN_DBI].md_cmp == NULL) {
+		mdb_default_cmp(txn, MAIN_DBI);
+	}
+
+	// Is the DB already open?
+	len = strlen(name);
+	for (i=2; i<txn->mt_numdbs; i++) {
+		if (!txn->mt_dbxs[i].md_name.mv_size) {
+			// Remember this free slot
+			if (!unused) unused = i;
+			continue;
+		}
+		if (len == txn->mt_dbxs[i].md_name.mv_size &&
+			!strncmp(name, txn->mt_dbxs[i].md_name.mv_data, len)) {
+			*dbi = i;
+			return MDB_SUCCESS;
+		}
+	}
+
+	// If no free slot and max hit, fail
+	if (!unused && txn->mt_numdbs >= txn->mt_env->me_maxdbs)
+		return MDB_DBS_FULL;
+
+	// Cannot mix named databases with some mainDB flags
+	if (txn->mt_dbs[MAIN_DBI].md_flags & (MDB_DUPSORT|MDB_INTEGERKEY))
+		return (flags & MDB_CREATE) ? MDB_INCOMPATIBLE : MDB_NOTFOUND;
+
+	// Find the DB info
+	dbflag = DB_NEW|DB_VALID;
+	exact = 0;
+	key.mv_size = len;
+	key.mv_data = (void *)name;
+	mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
+	rc = mdb_cursor_set(&mc, &key, &data, MDB_SET, &exact);
+	if (rc == MDB_SUCCESS) {
+		// make sure this is actually a DB
+		MDB_node *node = NODEPTR(mc.mc_pg[mc.mc_top], mc.mc_ki[mc.mc_top]);
+		if (!(node->mn_flags & F_SUBDATA))
+			return MDB_INCOMPATIBLE;
+	} else if (rc == MDB_NOTFOUND && (flags & MDB_CREATE)) {
+		// Create if requested
+		MDB_db dummy;
+		data.mv_size = sizeof(MDB_db);
+		data.mv_data = &dummy;
+		memset(&dummy, 0, sizeof(dummy));
+		dummy.md_root = P_INVALID;
+		dummy.md_flags = flags & PERSISTENT_FLAGS;
+		rc = mdb_cursor_put(&mc, &key, &data, F_SUBDATA);
+		dbflag |= DB_DIRTY;
+	}
+
+	// OK, got info, add to table
+	if (rc == MDB_SUCCESS) {
+		unsigned int slot = unused ? unused : txn->mt_numdbs;
+		txn->mt_dbxs[slot].md_name.mv_data = strdup(name);
+		txn->mt_dbxs[slot].md_name.mv_size = len;
+		txn->mt_dbxs[slot].md_rel = NULL;
+		txn->mt_dbflags[slot] = dbflag;
+		memcpy(&txn->mt_dbs[slot], data.mv_data, sizeof(MDB_db));
+		*dbi = slot;
+		mdb_default_cmp(txn, slot);
+		if (!unused) {
+			txn->mt_numdbs++;
+		}
+	}
+
+	return rc;
+	*/
+	return nil, nil
+}
+
+func (t *transaction) Stat(b Bucket) *Stat {
+	if (txn == NULL || arg == NULL || dbi >= txn->mt_numdbs)
+		return EINVAL;
+
+	if (txn->mt_dbflags[dbi] & DB_STALE) {
+		MDB_cursor mc;
+		MDB_xcursor mx;
+		/* Stale, must read the DB's root. cursor_init does it for us. */
+		mdb_cursor_init(&mc, txn, dbi, &mx);
+	}
+	return mdb_stat0(txn->mt_env, &txn->mt_dbs[dbi], arg);
+}
+
+func (t *transaction) BucketFlags(b Bucket) (int, error) {
+	/*
+	// We could return the flags for the FREE_DBI too but what's the point?
+	if (txn == NULL || dbi < MAIN_DBI || dbi >= txn->mt_numdbs)
+		return EINVAL;
+	*flags = txn->mt_dbs[dbi].md_flags & PERSISTENT_FLAGS;
+	return MDB_SUCCESS;
+	*/
+	return 0, nil
+}
+
+func (t *transaction) Drop(b Bucket int del) error {
+	/*
+	MDB_cursor *mc, *m2;
+	int rc;
+
+	if (!txn || !dbi || dbi >= txn->mt_numdbs || (unsigned)del > 1 || !(txn->mt_dbflags[dbi] & DB_VALID))
+		return EINVAL;
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
+		return EACCES;
+
+	rc = mdb_cursor_open(txn, dbi, &mc);
+	if (rc)
+		return rc;
+
+	rc = mdb_drop0(mc, mc->mc_db->md_flags & MDB_DUPSORT);
+	// Invalidate the dropped DB's cursors
+	for (m2 = txn->mt_cursors[dbi]; m2; m2 = m2->mc_next)
+		m2->mc_flags &= ~(C_INITIALIZED|C_EOF);
+	if (rc)
+		goto leave;
+
+	// Can't delete the main DB
+	if (del && dbi > MAIN_DBI) {
+		rc = mdb_del(txn, MAIN_DBI, &mc->mc_dbx->md_name, NULL);
+		if (!rc) {
+			txn->mt_dbflags[dbi] = DB_STALE;
+			mdb_dbi_close(txn->mt_env, dbi);
+		}
+	} else {
+		// reset the DB record, mark it dirty 
+		txn->mt_dbflags[dbi] |= DB_DIRTY;
+		txn->mt_dbs[dbi].md_depth = 0;
+		txn->mt_dbs[dbi].md_branch_pages = 0;
+		txn->mt_dbs[dbi].md_leaf_pages = 0;
+		txn->mt_dbs[dbi].md_overflow_pages = 0;
+		txn->mt_dbs[dbi].md_entries = 0;
+		txn->mt_dbs[dbi].md_root = P_INVALID;
+
+		txn->mt_flags |= MDB_TXN_DIRTY;
+	}
+leave:
+	mdb_cursor_close(mc);
+	return rc;
+	*/
+	return nil
+}
diff --git a/xcursor.go b/xcursor.go
index fa0e915..35571ab 100644
--- a/xcursor.go
+++ b/xcursor.go
@@ -6,3 +6,4 @@ type xcursor struct {
 	bucketx    *bucketx
 	bucketFlag int
 }
+