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git/odb/pack: promote IndexVersion to interface

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This commit is contained in:
Taylor Blau 2017-07-24 13:28:56 -06:00
parent 735619d3b3
commit 069035c105
10 changed files with 82 additions and 170 deletions
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8
git/odb/pack/index.go
View File

@ -1,6 +1,7 @@
package pack
import (
"bytes"
"io"
"github.com/git-lfs/git-lfs/errors"
@ -71,17 +72,16 @@ func (i *Index) Entry(name []byte) (*IndexEntry, error) {
// Find the midpoint between the upper and lower bounds.
mid := bounds.Left() + ((bounds.Right() - bounds.Left()) / 2)
// Search for the given object at that midpoint.
entry, cmp, err := i.version.Search(i, name, mid)
got, err := i.version.Name(i, mid)
if err != nil {
return nil, err
}
if cmp == 0 {
if cmp := bytes.Compare(name, got); cmp == 0 {
// If "cmp" is zero, that means the object at that index
// "at" had a SHA equal to the one given by name, and we
// are done.
return entry, nil
return i.version.Entry(i, mid)
} else if cmp < 0 {
// If the comparison is less than 0, we searched past
// the desired object, so limit the upper bound of the

16
git/odb/pack/index_decode.go
View File

@ -93,24 +93,26 @@ func DecodeIndex(r io.ReaderAt) (*Index, error) {
func decodeIndexHeader(r io.ReaderAt) (IndexVersion, error) {
hdr := make([]byte, 4)
if _, err := r.ReadAt(hdr, 0); err != nil {
return VersionUnknown, err
return nil, err
}
if bytes.Equal(hdr, indexHeader) {
vb := make([]byte, 4)
if _, err := r.ReadAt(vb, 4); err != nil {
return VersionUnknown, err
return nil, err
}
version := IndexVersion(binary.BigEndian.Uint32(vb))
version := binary.BigEndian.Uint32(vb)
switch version {
case V1, V2:
return version, nil
case 1:
return new(V1), nil
case 2:
return new(V2), nil
}
return version, &UnsupportedVersionErr{uint32(version)}
return nil, &UnsupportedVersionErr{uint32(version)}
}
return V1, nil
return new(V1), nil
}
// decodeIndexFanout decodes the fanout table given by "r" and beginning at the

2
git/odb/pack/index_decode_test.go
View File

@ -31,7 +31,6 @@ func TestDecodeIndexV2(t *testing.T) {
idx, err := DecodeIndex(bytes.NewReader(buf))
assert.NoError(t, err)
assert.Equal(t, V2, idx.version)
assert.EqualValues(t, 3, idx.Count())
}
@ -51,7 +50,6 @@ func TestDecodeIndexV1(t *testing.T) {
idx, err := DecodeIndex(bytes.NewReader(make([]byte, indexFanoutWidth)))
assert.NoError(t, err)
assert.Equal(t, V1, idx.version)
assert.EqualValues(t, 0, idx.Count())
}

2
git/odb/pack/index_test.go
View File

@ -166,7 +166,7 @@ func init() {
fanout: fanout,
// version is unimportant here, use V2 since it's more common in
// the wild.
version: V2,
version: new(V2),
// *bytes.Buffer does not implement io.ReaderAt, but
// *bytes.Reader does.

34
git/odb/pack/index_v1.go
View File

@ -1,36 +1,40 @@
package pack
import (
"bytes"
"encoding/binary"
)
const (
// V1 is an instance of IndexVersion corresponding to the V1 index file
// format.
V1 IndexVersion = 1
)
// V1 implements IndexVersion for v1 packfiles.
type V1 struct{}
// v1Search implements the IndexVersion.Search method for V1 packfiles.
func v1Search(idx *Index, name []byte, at int64) (*IndexEntry, int, error) {
// Name implements IndexVersion.Name by returning the 20 byte SHA-1 object name
// for the given entry at offset "at" in the v1 index file "idx".
func (v *V1) Name(idx *Index, at int64) ([]byte, error) {
var sha [20]byte
if _, err := idx.readAt(sha[:], v1ShaOffset(at)); err != nil {
return nil, 0, err
return nil, err
}
cmp := bytes.Compare(name, sha[:])
if cmp != 0 {
return nil, cmp, nil
}
return sha[:], nil
}
// Entry implements IndexVersion.Entry for v1 packfiles by parsing and returning
// the IndexEntry specified at the offset "at" in the given index file.
func (v *V1) Entry(idx *Index, at int64) (*IndexEntry, error) {
var offs [4]byte
if _, err := idx.readAt(offs[:], v1EntryOffset(at)); err != nil {
return nil, 0, err
return nil, err
}
return &IndexEntry{
PackOffset: uint64(binary.BigEndian.Uint32(offs[:])),
}, 0, nil
}, nil
}
// Width implements IndexVersion.Width() by returning the number of bytes that
// v1 packfile index header occupy.
func (v *V1) Width() int64 {
return indexV1Width
}
// v1ShaOffset returns the location of the SHA1 of an object given at "at".

29
git/odb/pack/index_v1_test.go
View File

@ -37,40 +37,19 @@ var (
V1Index = &Index{
fanout: V1IndexFanout,
version: V1,
version: new(V1),
}
)
func TestIndexV1SearchExact(t *testing.T) {
e, cmp, err := V1.Search(V1Index, V1IndexMediumSha, 1)
e, err := new(V1).Entry(V1Index, 1)
assert.NoError(t, err)
assert.Equal(t, 0, cmp)
assert.EqualValues(t, 2, e.PackOffset)
}
func TestIndexV1SearchSmall(t *testing.T) {
e, cmp, err := V1.Search(V1Index, V1IndexMediumSha, 0)
assert.NoError(t, err)
assert.Equal(t, 1, cmp)
assert.Nil(t, e)
}
func TestIndexV1SearchBig(t *testing.T) {
e, cmp, err := V1.Search(V1Index, V1IndexMediumSha, 2)
assert.NoError(t, err)
assert.Equal(t, -1, cmp)
assert.Nil(t, e)
}
func TestIndexV1SearchOutOfBounds(t *testing.T) {
e, cmp, err := V1.Search(V1Index, V1IndexMediumSha, 10)
assert.Nil(t, e)
assert.Equal(t, 0, cmp)
assert.Equal(t, ErrIndexOutOfBounds, err)
func TestIndexVersionWidthV1(t *testing.T) {
assert.EqualValues(t, 0, new(V1).Width())
}
func init() {

36
git/odb/pack/index_v2.go
View File

@ -1,31 +1,29 @@
package pack
import (
"bytes"
"encoding/binary"
)
const (
// V2 is an instance of IndexVersion corresponding to the V2 index file
// format.
V2 IndexVersion = 2
)
// V2 implements IndexVersion for v2 packfiles.
type V2 struct{}
// v2Search implements the IndexVersion.Search method for V2 packfiles.
func v2Search(idx *Index, name []byte, at int64) (*IndexEntry, int, error) {
// Name implements IndexVersion.Name by returning the 20 byte SHA-1 object name
// for the given entry at offset "at" in the v2 index file "idx".
func (v *V2) Name(idx *Index, at int64) ([]byte, error) {
var sha [20]byte
if _, err := idx.readAt(sha[:], v2ShaOffset(at)); err != nil {
return nil, 0, err
return nil, err
}
cmp := bytes.Compare(name, sha[:])
if cmp != 0 {
return nil, cmp, nil
}
return sha[:], nil
}
// Entry implements IndexVersion.Entry for v2 packfiles by parsing and returning
// the IndexEntry specified at the offset "at" in the given index file.
func (v *V2) Entry(idx *Index, at int64) (*IndexEntry, error) {
var offs [4]byte
if _, err := idx.readAt(offs[:], v2SmallOffsetOffset(at, int64(idx.Count()))); err != nil {
return nil, 0, err
return nil, err
}
loc := uint64(binary.BigEndian.Uint32(offs[:]))
@ -37,12 +35,18 @@ func v2Search(idx *Index, name []byte, at int64) (*IndexEntry, int, error) {
// offset.
var offs [8]byte
if _, err := idx.readAt(offs[:], int64(loc&0x7fffffff)); err != nil {
return nil, 0, err
return nil, err
}
loc = binary.BigEndian.Uint64(offs[:])
}
return &IndexEntry{PackOffset: loc}, 0, nil
return &IndexEntry{PackOffset: loc}, nil
}
// Width implements IndexVersion.Width() by returning the number of bytes that
// v2 packfile index header occupy.
func (v *V2) Width() int64 {
return indexV2Width
}
// v2ShaOffset returns the offset of a SHA1 given at "at" in the V2 index file.

32
git/odb/pack/index_v2_test.go
View File

@ -45,42 +45,28 @@ var (
V2Index = &Index{
fanout: V2IndexFanout,
version: V2,
version: new(V2),
}
)
func TestIndexV2SearchExact(t *testing.T) {
e, cmp, err := V2.Search(V2Index, V2IndexMediumSha, 1)
func TestIndexV2EntryExact(t *testing.T) {
e, err := new(V2).Entry(V2Index, 1)
assert.Equal(t, 0, cmp)
assert.NoError(t, err)
assert.EqualValues(t, 2, e.PackOffset)
}
func TestIndexV2SearchSmall(t *testing.T) {
e, cmp, err := V2.Search(V2Index, V2IndexMediumSha, 0)
func TestIndexV2EntryExtendedOffset(t *testing.T) {
e, err := new(V2).Entry(V2Index, 2)
assert.Equal(t, 1, cmp)
assert.NoError(t, err)
assert.Nil(t, e)
}
func TestIndexV2SearchBig(t *testing.T) {
e, cmp, err := V2.Search(V2Index, V2IndexMediumSha, 2)
assert.Equal(t, -1, cmp)
assert.NoError(t, err)
assert.Nil(t, e)
}
func TestIndexV2SearchExtendedOffset(t *testing.T) {
e, cmp, err := V2.Search(V2Index, V2IndexLargeSha, 2)
assert.Equal(t, 0, cmp)
assert.NoError(t, err)
assert.EqualValues(t, 3, e.PackOffset)
}
func TestIndexVersionWidthV2(t *testing.T) {
assert.EqualValues(t, 8, new(V2).Width())
}
func init() {
V2IndexFanout[1] = 1
V2IndexFanout[2] = 2

63
git/odb/pack/index_version.go
View File

@ -1,54 +1,23 @@
package pack
import (
"fmt"
"github.com/git-lfs/git-lfs/errors"
)
// IndexVersion is a constant type that represents the version of encoding used
// by a particular index version.
type IndexVersion uint32
type IndexVersion interface {
// Name returns the name of the object located at the given offset "at",
// in the Index file "idx".
//
// It returns an error if the object at that location could not be
// parsed.
Name(idx *Index, at int64) ([]byte, error)
const (
// VersionUnknown is the zero-value for IndexVersion, and represents an
// unknown version.
VersionUnknown IndexVersion = 0
)
// Entry parses and returns the full *IndexEntry located at the offset
// "at" in the Index file "idx".
//
// If there was an error parsing the IndexEntry at that location, it
// will be returned.
Entry(idx *Index, at int64) (*IndexEntry, error)
// Width returns the width of the header given in the respective version.
func (v IndexVersion) Width() int64 {
switch v {
case V2:
return indexV2Width
case V1:
return indexV1Width
}
panic(fmt.Sprintf("git/odb/pack: width unknown for pack version %d", v))
}
var (
// ErrIndexOutOfBounds is an error returned when the object lookup "at"
// (see: Search() below) is out of bounds.
ErrIndexOutOfBounds = errors.New("git/odb/pack: index is out of bounds")
)
// Search searches index "idx" for an object given by "name" at location "at".
//
// If will return the object if it was found, or a comparison determining
// whether to search above or below next.
//
// Otherwise, it will return an error.
func (v IndexVersion) Search(idx *Index, name []byte, at int64) (*IndexEntry, int, error) {
if at > int64(idx.Count()) {
return nil, 0, ErrIndexOutOfBounds
}
switch v {
case V2:
return v2Search(idx, name, at)
case V1:
return v1Search(idx, name, at)
}
return nil, 0, &UnsupportedVersionErr{Got: uint32(v)}
// Width returns the number of bytes occupied by the header of a
// particular index version.
Width() int64
}

30
git/odb/pack/index_version_test.go
View File

@ -1,30 +0,0 @@
package pack
import (
"testing"
"github.com/stretchr/testify/assert"
)
func TestIndexVersionWidthV1(t *testing.T) {
assert.EqualValues(t, 0, V1.Width())
}
func TestIndexVersionWidthV2(t *testing.T) {
assert.EqualValues(t, 8, V2.Width())
}
func TestIndexVersionWidthPanicsOnUnknownVersion(t *testing.T) {
v := IndexVersion(5)
defer func() {
err := recover()
if err == nil {
t.Fatal("git/odb/pack: expected IndexVersion.Width() to panic()")
}
assert.Equal(t, "git/odb/pack: width unknown for pack version 5", err)
}()
v.Width()
}