lunny/git-lfs
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

git/odb/pack: zlib-flate delta instructions before applying

Browse Source
This commit is contained in:
Taylor Blau 2017-09-06 22:50:19 -04:00
parent 64559268eb
commit 8888cd8183
2 changed files with 55 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
git/odb/pack/packfile.go
View File

@ -1,7 +1,9 @@
package pack
import (
"compress/zlib"
"io"
"io/ioutil"
"github.com/git-lfs/git-lfs/errors"
)
@ -125,8 +127,19 @@ func (p *Packfile) find(offset int64) (Chain, error) {
// Now load the delta to apply to the base, given at the offset
// "offset" and for length "size".
delta := make([]byte, size)
if _, err := p.r.ReadAt(delta, offset); err != nil {
//
// NB: The delta instructions are zlib compressed, so ensure
// that we uncompress the instructions first.
zr, err := zlib.NewReader(&OffsetReaderAt{
o: offset,
r: p.r,
})
if err != nil {
return nil, err
}
delta, err := ioutil.ReadAll(zr)
if err != nil {
return nil, err
}

70
git/odb/pack/packfile_test.go
View File

@ -80,9 +80,23 @@ func TestPackObjectReturnsObjectWithDeltaBaseOffset(t *testing.T) {
const original = "Hello"
compressed, _ := compress(original)
delta, err := compress(string([]byte{
0x05, // Source size: 5.
0x0e, // Destination size: 14.
0x91, // (1000 0001) (instruction=copy, bitmask=0001)
0x00, // (0000 0000) (offset=0)
0x05, // (0000 0101) (size=5)
0x09, // (0000 0111) (instruction=add, size=7)
// Contents: ...
',', ' ', 'w', 'o', 'r', 'l', 'd', '!', '\n',
}))
p := &Packfile{
idx: IndexWith(map[string]uint32{
"cccccccccccccccccccccccccccccccccccccccc": 32,
"cccccccccccccccccccccccccccccccccccccccc": uint32(32 + 1 + len(compressed)),
}),
r: bytes.NewReader(append(append([]byte{
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
@ -91,14 +105,10 @@ func TestPackObjectReturnsObjectWithDeltaBaseOffset(t *testing.T) {
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x35, // (0011 0101) (msb=0, type=blob, size=5)
}, compressed...), []byte{
0x6a, // (0110 1010) (msb=0, type=obj_ofs_delta, size=10)
0x11, // (0001 0001) (ofs_delta=-17, len(compressed))
0x7, // (0000 0111) (instruction=add, size=7)
// Contents: ...
',', ' ', 'w', 'o', 'r', 'l', 'd', '!', '\n',
}...)),
}, compressed...), append([]byte{
0x6e, // (0110 1010) (msb=0, type=obj_ofs_delta, size=10)
0x12, // (0001 0001) (ofs_delta=-17, len(compressed))
}, delta...)...)),
}
o, err := p.Object(DecodeHex(t, "cccccccccccccccccccccccccccccccccccccccc"))
@ -107,7 +117,7 @@ func TestPackObjectReturnsObjectWithDeltaBaseOffset(t *testing.T) {
assert.Equal(t, TypeBlob, o.Type())
unpacked, err := o.Unpack()
assert.Equal(t, []byte(original), unpacked)
assert.Equal(t, []byte(original+", world!\n"), unpacked)
assert.NoError(t, err)
}
@ -115,6 +125,22 @@ func TestPackfileObjectReturnsObjectWithDeltaBaseReference(t *testing.T) {
const original = "Hello!\n"
compressed, _ := compress(original)
delta, _ := compress(string([]byte{
0x07, // Source size: 7.
0x0e, // Destination size: 14.
0x91, // (1001 0001) (copy, smask=0001, omask=0001)
0x00, // (0000 0000) (offset=0)
0x05, // (0000 0101) (size=5)
0x7, // (0000 0111) (add, length=6)
',', ' ', 'w', 'o', 'r', 'l', 'd', // (data ...)
0x91, // (1001 0001) (copy, smask=0001, omask=0001)
0x05, // (0000 0101) (offset=5)
0x02, // (0000 0010) (size=2)
}))
p := &Packfile{
idx: IndexWith(map[string]uint32{
"cccccccccccccccccccccccccccccccccccccccc": 32,
@ -127,30 +153,14 @@ func TestPackfileObjectReturnsObjectWithDeltaBaseReference(t *testing.T) {
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x37, // (0011 0101) (msb=0, type=blob, size=7)
}, compressed...), []byte{
0x7f, // (0111 1111) (msb=0, type=obj_ref_delta, size=16)
}, compressed...), append([]byte{
0x7f, // (0111 1111) (msb=0, type=obj_ref_delta, size=15)
// SHA-1 "cccccccccccccccccccccccccccccccccccccccc",
// original blob contents is "Hello!\n"
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
// BEGIN OBJECT:
// "dddddddddddddddddddddddddddddddddddddddd":
0x07, // Source size: 7.
0x0d, // Destination size: 13.
0x91, // (1001 0001) (copy, smask=0001, omask=0001)
0x00, // (0000 0000) (offset=0)
0x05, // (0000 0101) (size=5)
0x6, // (0000 0111) (add, length=6)
' ', 'w', 'o', 'r', 'l', 'd', // (data ...)
0x91, // (1001 0001) (copy, smask=0001, omask=0001)
0x05, // (0000 0101) (offset=5)
0x02, // (0000 0010) (size=2)
}...)),
}, delta...)...)),
}
o, err := p.Object(DecodeHex(t, "dddddddddddddddddddddddddddddddddddddddd"))
@ -159,7 +169,7 @@ func TestPackfileObjectReturnsObjectWithDeltaBaseReference(t *testing.T) {
assert.Equal(t, TypeBlob, o.Type())
unpacked, err := o.Unpack()
assert.Equal(t, []byte("Hello world!\n"), unpacked)
assert.Equal(t, []byte("Hello, world!\n"), unpacked)
assert.NoError(t, err)
}