plumbing/format/idxfile: add new Index and MemoryIndex

plumbing/format/idxfile/decoder.go

@@ -17,6 +17,11 @@ var (
 	ErrMalformedIdxFile = errors.New("Malformed IDX file")
 )
 
+const (
+	fanout         = 256
+	objectIDLength = 20
+)
+
 // Decoder reads and decodes idx files from an input stream.
 type Decoder struct {
 	*bufio.Reader
@@ -27,13 +32,13 @@ func NewDecoder(r io.Reader) *Decoder {
 	return &Decoder{bufio.NewReader(r)}
 }
 
-// Decode reads from the stream and decode the content into the Idxfile struct.
-func (d *Decoder) Decode(idx *Idxfile) error {
+// Decode reads from the stream and decode the content into the MemoryIndex struct.
+func (d *Decoder) Decode(idx *MemoryIndex) error {
 	if err := validateHeader(d); err != nil {
 		return err
 	}
 
-	flow := []func(*Idxfile, io.Reader) error{
+	flow := []func(*MemoryIndex, io.Reader) error{
 		readVersion,
 		readFanout,
 		readObjectNames,
@@ -48,10 +53,6 @@ func (d *Decoder) Decode(idx *Idxfile) error {
 		}
 	}
 
-	if !idx.isValid() {
-		return ErrMalformedIdxFile
-	}
-
 	return nil
 }
 
@@ -68,7 +69,7 @@ func validateHeader(r io.Reader) error {
 	return nil
 }
 
-func readVersion(idx *Idxfile, r io.Reader) error {
+func readVersion(idx *MemoryIndex, r io.Reader) error {
 	v, err := binary.ReadUint32(r)
 	if err != nil {
 		return err
@@ -82,74 +83,92 @@ func readVersion(idx *Idxfile, r io.Reader) error {
 	return nil
 }
 
-func readFanout(idx *Idxfile, r io.Reader) error {
-	var err error
-	for i := 0; i < 255; i++ {
-		idx.Fanout[i], err = binary.ReadUint32(r)
+func readFanout(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		n, err := binary.ReadUint32(r)
 		if err != nil {
 			return err
 		}
+
+		idx.Fanout[k] = n
+		idx.FanoutMapping[k] = noMapping
 	}
 
-	idx.ObjectCount, err = binary.ReadUint32(r)
-	return err
+	return nil
 }
 
-func readObjectNames(idx *Idxfile, r io.Reader) error {
-	c := int(idx.ObjectCount)
-	new := make([]Entry, c)
-	for i := 0; i < c; i++ {
-		e := &new[i]
-		if _, err := io.ReadFull(r, e.Hash[:]); err != nil {
+func readObjectNames(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		var buckets uint32
+		if k == 0 {
+			buckets = idx.Fanout[k]
+		} else {
+			buckets = idx.Fanout[k] - idx.Fanout[k-1]
+		}
+
+		if buckets == 0 {
+			continue
+		}
+
+		if buckets < 0 {
+			return ErrMalformedIdxFile
+		}
+
+		idx.FanoutMapping[k] = len(idx.Names)
+
+		nameLen := int(buckets * objectIDLength)
+		bin := make([]byte, nameLen)
+		if _, err := io.ReadFull(r, bin); err != nil {
 			return err
 		}
 
-		idx.Entries = append(idx.Entries, e)
+		idx.Names = append(idx.Names, bin)
+		idx.Offset32 = append(idx.Offset32, make([]byte, buckets*4))
+		idx.Crc32 = append(idx.Crc32, make([]byte, buckets*4))
 	}
 
 	return nil
 }
 
-func readCRC32(idx *Idxfile, r io.Reader) error {
-	c := int(idx.ObjectCount)
-	for i := 0; i < c; i++ {
-		if err := binary.Read(r, &idx.Entries[i].CRC32); err != nil {
-			return err
+func readCRC32(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		if pos := idx.FanoutMapping[k]; pos != noMapping {
+			if _, err := io.ReadFull(r, idx.Crc32[pos]); err != nil {
+				return err
+			}
 		}
 	}
 
 	return nil
 }
 
-func readOffsets(idx *Idxfile, r io.Reader) error {
-	c := int(idx.ObjectCount)
-
-	for i := 0; i < c; i++ {
-		o, err := binary.ReadUint32(r)
-		if err != nil {
-			return err
+func readOffsets(idx *MemoryIndex, r io.Reader) error {
+	var o64cnt int
+	for k := 0; k < fanout; k++ {
+		if pos := idx.FanoutMapping[k]; pos != noMapping {
+			if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil {
+				return err
+			}
+
+			for p := 0; p < len(idx.Offset32[pos]); p += 4 {
+				if idx.Offset32[pos][p]&(byte(1)<<7) > 0 {
+					o64cnt++
+				}
+			}
 		}
-
-		idx.Entries[i].Offset = uint64(o)
 	}
 
-	for i := 0; i < c; i++ {
-		if idx.Entries[i].Offset <= offsetLimit {
-			continue
-		}
-
-		o, err := binary.ReadUint64(r)
-		if err != nil {
+	if o64cnt > 0 {
+		idx.Offset64 = make([]byte, o64cnt*8)
+		if _, err := io.ReadFull(r, idx.Offset64); err != nil {
 			return err
 		}
-
-		idx.Entries[i].Offset = o
 	}
 
 	return nil
 }
 
-func readChecksums(idx *Idxfile, r io.Reader) error {
+func readChecksums(idx *MemoryIndex, r io.Reader) error {
 	if _, err := io.ReadFull(r, idx.PackfileChecksum[:]); err != nil {
 		return err
 	}

plumbing/format/idxfile/decoder_test.go

@@ -4,11 +4,12 @@ import (
 	"bytes"
 	"encoding/base64"
 	"fmt"
+	"io"
+	"io/ioutil"
 	"testing"
 
+	"gopkg.in/src-d/go-git.v4/plumbing"
 	. "gopkg.in/src-d/go-git.v4/plumbing/format/idxfile"
-	"gopkg.in/src-d/go-git.v4/plumbing/format/packfile"
-	"gopkg.in/src-d/go-git.v4/storage/memory"
 
 	. "gopkg.in/check.v1"
 	"gopkg.in/src-d/go-git-fixtures.v3"
@@ -26,51 +27,34 @@ func (s *IdxfileSuite) TestDecode(c *C) {
 	f := fixtures.Basic().One()
 
 	d := NewDecoder(f.Idx())
-	idx := &Idxfile{}
+	idx := new(MemoryIndex)
 	err := d.Decode(idx)
 	c.Assert(err, IsNil)
 
-	c.Assert(idx.Entries, HasLen, 31)
-	c.Assert(idx.Entries[0].Hash.String(), Equals, "1669dce138d9b841a518c64b10914d88f5e488ea")
-	c.Assert(idx.Entries[0].Offset, Equals, uint64(615))
-	c.Assert(idx.Entries[0].CRC32, Equals, uint32(3645019190))
+	count, _ := idx.Count()
+	c.Assert(count, Equals, int64(31))
 
-	c.Assert(fmt.Sprintf("%x", idx.IdxChecksum), Equals, "fb794f1ec720b9bc8e43257451bd99c4be6fa1c9")
-	c.Assert(fmt.Sprintf("%x", idx.PackfileChecksum), Equals, f.PackfileHash.String())
-}
-
-func (s *IdxfileSuite) TestDecodeCRCs(c *C) {
-	f := fixtures.Basic().ByTag("ofs-delta").One()
-
-	scanner := packfile.NewScanner(f.Packfile())
-	storage := memory.NewStorage()
-
-	pd, err := packfile.NewDecoder(scanner, storage)
+	hash := plumbing.NewHash("1669dce138d9b841a518c64b10914d88f5e488ea")
+	ok, err := idx.Contains(hash)
 	c.Assert(err, IsNil)
-	_, err = pd.Decode()
-	c.Assert(err, IsNil)
-
-	i := pd.Index().ToIdxFile()
-	i.Version = VersionSupported
+	c.Assert(ok, Equals, true)
 
-	buf := bytes.NewBuffer(nil)
-	e := NewEncoder(buf)
-	_, err = e.Encode(i)
+	offset, err := idx.FindOffset(hash)
 	c.Assert(err, IsNil)
+	c.Assert(offset, Equals, int64(615))
 
-	idx := &Idxfile{}
-
-	d := NewDecoder(buf)
-	err = d.Decode(idx)
+	crc32, err := idx.FindCRC32(hash)
 	c.Assert(err, IsNil)
+	c.Assert(crc32, Equals, uint32(3645019190))
 
-	c.Assert(idx.Entries, DeepEquals, i.Entries)
+	c.Assert(fmt.Sprintf("%x", idx.IdxChecksum), Equals, "fb794f1ec720b9bc8e43257451bd99c4be6fa1c9")
+	c.Assert(fmt.Sprintf("%x", idx.PackfileChecksum), Equals, f.PackfileHash.String())
 }
 
 func (s *IdxfileSuite) TestDecode64bitsOffsets(c *C) {
 	f := bytes.NewBufferString(fixtureLarge4GB)
 
-	idx := &Idxfile{}
+	idx := new(MemoryIndex)
 
 	d := NewDecoder(base64.NewDecoder(base64.StdEncoding, f))
 	err := d.Decode(idx)
@@ -88,29 +72,22 @@ func (s *IdxfileSuite) TestDecode64bitsOffsets(c *C) {
 		"35858be9c6f5914cbe6768489c41eb6809a2bceb": 5924278919,
 	}
 
-	for _, e := range idx.Entries {
-		c.Assert(expected[e.Hash.String()], Equals, e.Offset)
-	}
-}
-
-func (s *IdxfileSuite) TestDecode64bitsOffsetsIdempotent(c *C) {
-	f := bytes.NewBufferString(fixtureLarge4GB)
-
-	expected := &Idxfile{}
-
-	d := NewDecoder(base64.NewDecoder(base64.StdEncoding, f))
-	err := d.Decode(expected)
+	iter, err := idx.Entries()
 	c.Assert(err, IsNil)
 
-	buf := bytes.NewBuffer(nil)
-	_, err = NewEncoder(buf).Encode(expected)
-	c.Assert(err, IsNil)
+	var entries int
+	for {
+		e, err := iter.Next()
+		if err == io.EOF {
+			break
+		}
+		c.Assert(err, IsNil)
+		entries++
 
-	idx := &Idxfile{}
-	err = NewDecoder(buf).Decode(idx)
-	c.Assert(err, IsNil)
+		c.Assert(expected[e.Hash.String()], Equals, e.Offset)
+	}
 
-	c.Assert(idx.Entries, DeepEquals, expected.Entries)
+	c.Assert(entries, Equals, len(expected))
 }
 
 const fixtureLarge4GB = `/3RPYwAAAAIAAAAAAAAAAAAAAAAAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEAAAABAAAAAQAAAAEA
@@ -139,3 +116,30 @@ AAAAAAAMgAAAAQAAAI6AAAACgAAAA4AAAASAAAAFAAAAAV9Qam8AAAABYR1ShwAAAACdxfYxAAAA
 ANz1Di4AAAABPUnxJAAAAADNxzlGr6vCJpIFz4XaG/fi/f9C9zgQ8ptKSQpfQ1NMJBGTDTxxYGGp
 ch2xUA==
 `
+
+func BenchmarkDecode(b *testing.B) {
+	if err := fixtures.Init(); err != nil {
+		b.Errorf("unexpected error initializing fixtures: %s", err)
+	}
+
+	f := fixtures.Basic().One()
+	fixture, err := ioutil.ReadAll(f.Idx())
+	if err != nil {
+		b.Errorf("unexpected error reading idx file: %s", err)
+	}
+
+	defer func() {
+		if err := fixtures.Clean(); err != nil {
+			b.Errorf("unexpected error cleaning fixtures: %s", err)
+		}
+	}()
+
+	for i := 0; i < b.N; i++ {
+		f := bytes.NewBuffer(fixture)
+		idx := new(MemoryIndex)
+		d := NewDecoder(f)
+		if err := d.Decode(idx); err != nil {
+			b.Errorf("unexpected error decoding: %s", err)
+		}
+	}
+}