Add freelist page type.

bucket.go

@@ -1,11 +1,5 @@
 package bolt
 
-var (
-	InvalidBucketError = &Error{"invalid bucket", nil}
-)
-
-type bucketid uint32
-
 type Bucket struct {
 	*bucket
 	name        string
@@ -14,8 +8,6 @@ type Bucket struct {
 }
 
 type bucket struct {
-	id    bucketid
-	flags uint32
 	root  pgid
 }
 

db.go

@@ -146,18 +146,34 @@ func (db *DB) init() error {
 	db.pageSize = db.os.Getpagesize()
 
 	// Create two meta pages on a buffer.
-	buf := make([]byte, db.pageSize*2)
+	buf := make([]byte, db.pageSize*4)
 	for i := 0; i < 2; i++ {
 		p := db.pageInBuffer(buf[:], pgid(i))
 		p.id = pgid(i)
 		p.flags = p_meta
 
+		// Initialize the meta page.
 		m := p.meta()
 		m.magic = magic
 		m.version = Version
 		m.pageSize = uint32(db.pageSize)
+		m.version = Version
+		m.free = 3
+		m.sys.root = 4
 	}
 
+	// Write an empty freelist at page 3.
+	p := db.pageInBuffer(buf[:], pgid(2))
+	p.id = pgid(3)
+	p.flags = p_freelist
+	p.count = 0
+
+	// Write an empty leaf page at page 4.
+	p = db.pageInBuffer(buf[:], pgid(3))
+	p.id = pgid(4)
+	p.flags = p_leaf
+	p.count = 0
+
 	// Write the buffer to our data file.
 	if _, err := db.metafile.WriteAt(buf, 0); err != nil {
 		return err

meta.go

@@ -14,6 +14,7 @@ type meta struct {
 	pageSize uint32
 	pgid     pgid
 	txnid    txnid
+	free     pgid
 	sys      bucket
 }
 

page.go

@@ -11,9 +11,10 @@ const minKeysPerPage = 2
 const maxNodesPerPage = 65535
 
 const (
-	p_branch = 0x01
-	p_leaf   = 0x02
-	p_meta   = 0x04
+	p_branch   = 0x01
+	p_leaf     = 0x02
+	p_meta     = 0x04
+	p_freelist = 0x08
 )
 
 type pgid uint64
@@ -40,3 +41,8 @@ func (p *page) lnode(index int) *lnode {
 func (p *page) bnode(index int) *bnode {
 	return &((*[maxNodesPerPage]bnode)(unsafe.Pointer(&p.ptr)))[index]
 }
+
+// freelist retrieves a list of page ids from a freelist page.
+func (p *page) freelist() []pgid {
+	return ((*[maxNodesPerPage]pgid)(unsafe.Pointer(&p.ptr)))[0:p.count]
+}