introduce a freelist interface

This introduces an interface for the freelist, splits it into two concrete
implementations.

fixes etcd-io#773

Signed-off-by: Thomas Jungblut <[email protected]>

allocate_test.go

@@ -4,12 +4,13 @@ import (
  "testing"
 
  "go.etcd.io/bbolt/internal/common"
+ "go.etcd.io/bbolt/internal/freelist"
 )
 
 func TestTx_allocatePageStats(t *testing.T) {
- f := newTestFreelist()
+ f := freelist.NewArray()
  ids := []common.Pgid{2, 3}
- f.readIDs(ids)
+ f.Init(ids)
 
  tx := &Tx{
  db: &DB{
@@ -22,7 +23,7 @@ func TestTx_allocatePageStats(t *testing.T) {
 
  txStats := tx.Stats()
  prePageCnt := txStats.GetPageCount()
- allocateCnt := f.free_count()
+ allocateCnt := f.FreeCount()
 
  if _, err := tx.allocate(allocateCnt); err != nil {
  t.Fatal(err)

bucket.go

@@ -903,7 +903,7 @@ func (b *Bucket) free() {
  var tx = b.tx
  b.forEachPageNode(func(p *common.Page, n *node, _ int) {
  if p != nil {
- tx.db.freelist.free(tx.meta.Txid(), p)
+ tx.db.freelist.Free(tx.meta.Txid(), p)
  } else {
  n.free()
  }

bucket_test.go

@@ -430,6 +430,9 @@ func TestBucket_Delete_FreelistOverflow(t *testing.T) {
  if reopenFreePages := db.Stats().FreePageN; freePages != reopenFreePages {
  t.Fatalf("expected %d free pages, got %+v", freePages, db.Stats())
  }
+ if reopenPendingPages := db.Stats().PendingPageN; reopenPendingPages != 0 {
+ t.Fatalf("expected no pending pages, got %+v", db.Stats())
+ }
 }
 
 // Ensure that deleting of non-existing key is a no-op.

cmd/bbolt/command_version.go

@@ -5,6 +5,7 @@ import (
  "runtime"
 
  "github.com/spf13/cobra"
+
  "go.etcd.io/bbolt/version"
 )
 

db.go

@@ -13,6 +13,7 @@ import (
 
  berrors "go.etcd.io/bbolt/errors"
  "go.etcd.io/bbolt/internal/common"
+ fl "go.etcd.io/bbolt/internal/freelist"
 )
 
 // The time elapsed between consecutive file locking attempts.
@@ -134,8 +135,9 @@ type DB struct {
  rwtx *Tx
  txs []*Tx
 
- freelist *freelist
- freelistLoad sync.Once
+ freelist fl.Freelist
+ freelistSerializer fl.Serializable
+ freelistLoad sync.Once
 
  pagePool sync.Pool
 
@@ -190,6 +192,7 @@ func Open(path string, mode os.FileMode, options *Options) (db *DB, err error) {
  db.NoFreelistSync = options.NoFreelistSync
  db.PreLoadFreelist = options.PreLoadFreelist
  db.FreelistType = options.FreelistType
+ db.freelistSerializer = fl.Serializer{}
  db.Mlock = options.Mlock
 
  // Set default values for later DB operations.
@@ -419,12 +422,13 @@ func (db *DB) loadFreelist() {
  db.freelist = newFreelist(db.FreelistType)
  if !db.hasSyncedFreelist() {
  // Reconstruct free list by scanning the DB.
- db.freelist.readIDs(db.freepages())
+ db.freelist.Init(db.freepages())
  } else {
  // Read free list from freelist page.
- db.freelist.read(db.page(db.meta().Freelist()))
+ db.freelistSerializer.Read(db.freelist, db.page(db.meta().Freelist()))
  }
- db.stats.FreePageN = db.freelist.free_count()
+ db.stats.FreePageN = db.freelist.FreeCount()
+ db.stats.PendingPageN = db.freelist.PendingCount()
  })
 }
 
@@ -854,14 +858,14 @@ func (db *DB) freePages() {
  minid = db.txs[0].meta.Txid()
  }
  if minid > 0 {
- db.freelist.release(minid - 1)
+ db.freelist.Release(minid - 1)
  }
  // Release unused txid extents.
  for _, t := range db.txs {
- db.freelist.releaseRange(minid, t.meta.Txid()-1)
+ db.freelist.ReleaseRange(minid, t.meta.Txid()-1)
  minid = t.meta.Txid() + 1
  }
- db.freelist.releaseRange(minid, common.Txid(0xFFFFFFFFFFFFFFFF))
+ db.freelist.ReleaseRange(minid, common.Txid(0xFFFFFFFFFFFFFFFF))
  // Any page both allocated and freed in an extent is safe to release.
 }
 
@@ -1176,7 +1180,7 @@ func (db *DB) allocate(txid common.Txid, count int) (*common.Page, error) {
  p.SetOverflow(uint32(count - 1))
 
  // Use pages from the freelist if they are available.
- p.SetId(db.freelist.allocate(txid, count))
+ p.SetId(db.freelist.Allocate(txid, count))
  if p.Id() != 0 {
  return p, nil
  }
@@ -1282,6 +1286,13 @@ func (db *DB) freepages() []common.Pgid {
  return fids
 }
 
+func newFreelist(freelistType FreelistType) fl.Freelist {
+ if freelistType == FreelistMapType {
+ return fl.NewHashMap()
+ }
+ return fl.NewArray()
+}
+
 // Options represents the options that can be set when opening a database.
 type Options struct {
  // Timeout is the amount of time to wait to obtain a file lock.