1 files changed, 355 insertions, 0 deletions
diff --git a/rwtransaction.go b/rwtransaction.go
new file mode 100644
index 0000000..e22c766
--- /dev/null
+++ b/rwtransaction.go
@@ -0,0 +1,355 @@
+package bolt
+
+import (
+	"sort"
+	"unsafe"
+)
+
+// RWTransaction represents a transaction that can read and write data.
+// Only one read/write transaction can be active for a database at a time.
+// RWTransaction is composed of a read-only Transaction so it can also use
+// functions provided by Transaction.
+type RWTransaction struct {
+	Transaction
+	nodes   map[pgid]*node
+	pending []*node
+}
+
+// init initializes the transaction.
+func (t *RWTransaction) init(db *DB) {
+	t.Transaction.init(db)
+	t.pages = make(map[pgid]*page)
+
+	// Increment the transaction id.
+	t.meta.txnid += txnid(1)
+}
+
+// CreateBucket creates a new bucket.
+// Returns an error if the bucket already exists, if the bucket name is blank, or if the bucket name is too long.
+func (t *RWTransaction) CreateBucket(name string) error {
+	// Check if bucket already exists.
+	if b := t.Bucket(name); b != nil {
+		return ErrBucketExists
+	} else if len(name) == 0 {
+		return ErrBucketNameRequired
+	} else if len(name) > MaxBucketNameSize {
+		return ErrBucketNameTooLarge
+	}
+
+	// Create a blank root leaf page.
+	p, err := t.allocate(1)
+	if err != nil {
+		return err
+	}
+	p.flags = leafPageFlag
+
+	// Add bucket to buckets page.
+	t.buckets.put(name, &bucket{root: p.id})
+
+	return nil
+}
+
+// CreateBucketIfNotExists creates a new bucket if it doesn't already exist.
+// Returns an error if the bucket name is blank, or if the bucket name is too long.
+func (t *RWTransaction) CreateBucketIfNotExists(name string) error {
+	err := t.CreateBucket(name)
+	if err != nil && err != ErrBucketExists {
+		return err
+	}
+	return nil
+}
+
+// DeleteBucket deletes a bucket.
+// Returns an error if the bucket cannot be found.
+func (t *RWTransaction) DeleteBucket(name string) error {
+	if b := t.Bucket(name); b == nil {
+		return ErrBucketNotFound
+	}
+
+	// Remove from buckets page.
+	t.buckets.del(name)
+
+	// TODO(benbjohnson): Free all pages.
+
+	return nil
+}
+
+// NextSequence returns an autoincrementing integer for the bucket.
+func (t *RWTransaction) NextSequence(name string) (int, error) {
+	// Check if bucket already exists.
+	b := t.Bucket(name)
+	if b == nil {
+		return 0, ErrBucketNotFound
+	}
+
+	// Make sure next sequence number will not be larger than the maximum
+	// integer size of the system.
+	if b.bucket.sequence == uint64(maxInt) {
+		return 0, ErrSequenceOverflow
+	}
+
+	// Increment and return the sequence.
+	b.bucket.sequence++
+
+	return int(b.bucket.sequence), nil
+}
+
+// Put sets the value for a key inside of the named bucket.
+// If the key exist then its previous value will be overwritten.
+// Returns an error if the bucket is not found, if the key is blank, if the key is too large, or if the value is too large.
+func (t *RWTransaction) Put(name string, key []byte, value []byte) error {
+	b := t.Bucket(name)
+	if b == nil {
+		return ErrBucketNotFound
+	}
+
+	// Validate the key and data size.
+	if len(key) == 0 {
+		return ErrKeyRequired
+	} else if len(key) > MaxKeySize {
+		return ErrKeyTooLarge
+	} else if len(value) > MaxValueSize {
+		return ErrValueTooLarge
+	}
+
+	// Move cursor to correct position.
+	c := b.cursor()
+	c.Seek(key)
+
+	// Insert the key/value.
+	c.node(t).put(key, key, value, 0)
+
+	return nil
+}
+
+// Delete removes a key from the named bucket.
+// If the key does not exist then nothing is done and a nil error is returned.
+// Returns an error if the bucket cannot be found.
+func (t *RWTransaction) Delete(name string, key []byte) error {
+	b := t.Bucket(name)
+	if b == nil {
+		return ErrBucketNotFound
+	}
+
+	// Move cursor to correct position.
+	c := b.cursor()
+	c.Seek(key)
+
+	// Delete the node if we have a matching key.
+	c.node(t).del(key)
+
+	return nil
+}
+
+// Commit writes all changes to disk and updates the meta page.
+// Returns an error if a disk write error occurs.
+func (t *RWTransaction) Commit() error {
+	defer t.close()
+
+	// TODO(benbjohnson): Use vectorized I/O to write out dirty pages.
+
+	// Rebalance and spill data onto dirty pages.
+	t.rebalance()
+	t.spill()
+
+	// Spill buckets page.
+	p, err := t.allocate((t.buckets.size() / t.db.pageSize) + 1)
+	if err != nil {
+		return err
+	}
+	t.buckets.write(p)
+
+	// Write dirty pages to disk.
+	if err := t.write(); err != nil {
+		return err
+	}
+
+	// Update the meta.
+	t.meta.buckets = p.id
+
+	// Write meta to disk.
+	if err := t.writeMeta(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Rollback closes the transaction and ignores all previous updates.
+func (t *RWTransaction) Rollback() {
+	t.close()
+}
+
+func (t *RWTransaction) close() {
+	t.db.rwlock.Unlock()
+}
+
+// allocate returns a contiguous block of memory starting at a given page.
+func (t *RWTransaction) allocate(count int) (*page, error) {
+	p, err := t.db.allocate(count)
+	if err != nil {
+		return nil, err
+	}
+
+	// Save to our page cache.
+	t.pages[p.id] = p
+
+	return p, nil
+}
+
+// rebalance attempts to balance all nodes.
+func (t *RWTransaction) rebalance() {
+	for _, n := range t.nodes {
+		n.rebalance()
+	}
+}
+
+// spill writes all the nodes to dirty pages.
+func (t *RWTransaction) spill() error {
+	// Keep track of the current root nodes.
+	// We will update this at the end once all nodes are created.
+	type root struct {
+		node *node
+		pgid pgid
+	}
+	var roots []root
+
+	// Sort nodes by highest depth first.
+	nodes := make(nodesByDepth, 0, len(t.nodes))
+	for _, n := range t.nodes {
+		nodes = append(nodes, n)
+	}
+	sort.Sort(nodes)
+
+	// Spill nodes by deepest first.
+	for i := 0; i < len(nodes); i++ {
+		n := nodes[i]
+
+		// Save existing root buckets for later.
+		if n.parent == nil && n.pgid != 0 {
+			roots = append(roots, root{n, n.pgid})
+		}
+
+		// Split nodes into appropriate sized nodes.
+		// The first node in this list will be a reference to n to preserve ancestry.
+		newNodes := n.split(t.db.pageSize)
+		t.pending = newNodes
+
+		// If this is a root node that split then create a parent node.
+		if n.parent == nil && len(newNodes) > 1 {
+			n.parent = &node{transaction: t, isLeaf: false}
+			nodes = append(nodes, n.parent)
+		}
+
+		// Add node's page to the freelist.
+		if n.pgid > 0 {
+			t.db.freelist.free(t.id(), t.page(n.pgid))
+		}
+
+		// Write nodes to dirty pages.
+		for i, newNode := range newNodes {
+			// Allocate contiguous space for the node.
+			p, err := t.allocate((newNode.size() / t.db.pageSize) + 1)
+			if err != nil {
+				return err
+			}
+
+			// Write the node to the page.
+			newNode.write(p)
+			newNode.pgid = p.id
+			newNode.parent = n.parent
+
+			// The first node should use the existing entry, other nodes are inserts.
+			var oldKey []byte
+			if i == 0 {
+				oldKey = n.key
+			} else {
+				oldKey = newNode.inodes[0].key
+			}
+
+			// Update the parent entry.
+			if newNode.parent != nil {
+				newNode.parent.put(oldKey, newNode.inodes[0].key, nil, newNode.pgid)
+			}
+		}
+
+		t.pending = nil
+	}
+
+	// Update roots with new roots.
+	for _, root := range roots {
+		t.buckets.updateRoot(root.pgid, root.node.root().pgid)
+	}
+
+	// Clear out nodes now that they are all spilled.
+	t.nodes = make(map[pgid]*node)
+
+	return nil
+}
+
+// write writes any dirty pages to disk.
+func (t *RWTransaction) write() error {
+	// Sort pages by id.
+	pages := make(pages, 0, len(t.pages))
+	for _, p := range t.pages {
+		pages = append(pages, p)
+	}
+	sort.Sort(pages)
+
+	// Write pages to disk in order.
+	for _, p := range pages {
+		size := (int(p.overflow) + 1) * t.db.pageSize
+		buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:size]
+		offset := int64(p.id) * int64(t.db.pageSize)
+		if _, err := t.db.file.WriteAt(buf, offset); err != nil {
+			return err
+		}
+	}
+
+	// Clear out page cache.
+	t.pages = make(map[pgid]*page)
+
+	return nil
+}
+
+// writeMeta writes the meta to the disk.
+func (t *RWTransaction) writeMeta() error {
+	// Create a temporary buffer for the meta page.
+	buf := make([]byte, t.db.pageSize)
+	p := t.db.pageInBuffer(buf, 0)
+	t.meta.write(p)
+
+	// Write the meta page to file.
+	t.db.metafile.WriteAt(buf, int64(p.id)*int64(t.db.pageSize))
+
+	return nil
+}
+
+// node creates a node from a page and associates it with a given parent.
+func (t *RWTransaction) node(pgid pgid, parent *node) *node {
+	// Retrieve node if it has already been fetched.
+	if n := t.nodes[pgid]; n != nil {
+		return n
+	}
+
+	// Otherwise create a branch and cache it.
+	n := &node{transaction: t, parent: parent}
+	if n.parent != nil {
+		n.depth = n.parent.depth + 1
+	}
+	n.read(t.page(pgid))
+	t.nodes[pgid] = n
+
+	return n
+}
+
+// dereference removes all references to the old mmap.
+func (t *RWTransaction) dereference() {
+	for _, n := range t.nodes {
+		n.dereference()
+	}
+
+	for _, n := range t.pending {
+		n.dereference()
+	}
+}