Move all C code into repo.

1 files changed, 3557 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
+}