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authorPaulo Gomes <pjbgf@linux.com>2023-11-06 21:31:10 +0000
committerPaulo Gomes <pjbgf@linux.com>2023-11-06 21:38:24 +0000
commitf7cd844ced42685ed1e6676b0598f064ea5a5bc8 (patch)
tree1bdb82b57f5bf971f2bc8acac21678b34af73f4c /plumbing/format/packfile/patch_delta.go
parentcf196ea5ba6c8b16712a9868cc2d4cca4f287ae4 (diff)
downloadgo-git-f7cd844ced42685ed1e6676b0598f064ea5a5bc8.tar.gz
plumbing: format/packfile, Refactor patch delta
The changes aim to simplify the code and reduce duplication. Signed-off-by: Paulo Gomes <pjbgf@linux.com>
Diffstat (limited to 'plumbing/format/packfile/patch_delta.go')
-rw-r--r--plumbing/format/packfile/patch_delta.go187
1 files changed, 75 insertions, 112 deletions
diff --git a/plumbing/format/packfile/patch_delta.go b/plumbing/format/packfile/patch_delta.go
index 67c20ff..960769c 100644
--- a/plumbing/format/packfile/patch_delta.go
+++ b/plumbing/format/packfile/patch_delta.go
@@ -18,7 +18,33 @@ import (
// and https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js
// for details about the delta format.
-const deltaSizeMin = 4
+var (
+ ErrInvalidDelta = errors.New("invalid delta")
+ ErrDeltaCmd = errors.New("wrong delta command")
+)
+
+const (
+ payload = 0x7f // 0111 1111
+ continuation = 0x80 // 1000 0000
+)
+
+type offset struct {
+ mask byte
+ shift uint
+}
+
+var offsets = []offset{
+ {mask: 0x01, shift: 0},
+ {mask: 0x02, shift: 8},
+ {mask: 0x04, shift: 16},
+ {mask: 0x08, shift: 24},
+}
+
+var sizes = []offset{
+ {mask: 0x10, shift: 0},
+ {mask: 0x20, shift: 8},
+ {mask: 0x40, shift: 16},
+}
// ApplyDelta writes to target the result of applying the modification deltas in delta to base.
func ApplyDelta(target, base plumbing.EncodedObject, delta []byte) (err error) {
@@ -59,11 +85,6 @@ func ApplyDelta(target, base plumbing.EncodedObject, delta []byte) (err error) {
return err
}
-var (
- ErrInvalidDelta = errors.New("invalid delta")
- ErrDeltaCmd = errors.New("wrong delta command")
-)
-
// PatchDelta returns the result of applying the modification deltas in delta to src.
// An error will be returned if delta is corrupted (ErrDeltaLen) or an action command
// is not copy from source or copy from delta (ErrDeltaCmd).
@@ -121,7 +142,8 @@ func ReaderFromDelta(base plumbing.EncodedObject, deltaRC io.Reader) (io.ReadClo
return
}
- if isCopyFromSrc(cmd) {
+ switch {
+ case isCopyFromSrc(cmd):
offset, err := decodeOffsetByteReader(cmd, deltaBuf)
if err != nil {
_ = dstWr.CloseWithError(err)
@@ -174,7 +196,8 @@ func ReaderFromDelta(base plumbing.EncodedObject, deltaRC io.Reader) (io.ReadClo
}
remainingTargetSz -= sz
basePos += sz
- } else if isCopyFromDelta(cmd) {
+
+ case isCopyFromDelta(cmd):
sz := uint(cmd) // cmd is the size itself
if invalidSize(sz, targetSz) {
_ = dstWr.CloseWithError(ErrInvalidDelta)
@@ -186,10 +209,12 @@ func ReaderFromDelta(base plumbing.EncodedObject, deltaRC io.Reader) (io.ReadClo
}
remainingTargetSz -= sz
- } else {
+
+ default:
_ = dstWr.CloseWithError(ErrDeltaCmd)
return
}
+
if remainingTargetSz <= 0 {
_ = dstWr.Close()
return
@@ -201,7 +226,7 @@ func ReaderFromDelta(base plumbing.EncodedObject, deltaRC io.Reader) (io.ReadClo
}
func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
- if len(delta) < deltaSizeMin {
+ if len(delta) < minCopySize {
return ErrInvalidDelta
}
@@ -222,7 +247,9 @@ func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
cmd = delta[0]
delta = delta[1:]
- if isCopyFromSrc(cmd) {
+
+ switch {
+ case isCopyFromSrc(cmd):
var offset, sz uint
var err error
offset, delta, err = decodeOffset(cmd, delta)
@@ -241,7 +268,8 @@ func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
}
dst.Write(src[offset : offset+sz])
remainingTargetSz -= sz
- } else if isCopyFromDelta(cmd) {
+
+ case isCopyFromDelta(cmd):
sz := uint(cmd) // cmd is the size itself
if invalidSize(sz, targetSz) {
return ErrInvalidDelta
@@ -254,7 +282,8 @@ func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
dst.Write(delta[0:sz])
remainingTargetSz -= sz
delta = delta[sz:]
- } else {
+
+ default:
return ErrDeltaCmd
}
@@ -408,48 +437,24 @@ func decodeLEB128ByteReader(input io.ByteReader) (uint, error) {
return num, nil
}
-const (
- payload = 0x7f // 0111 1111
- continuation = 0x80 // 1000 0000
-)
-
func isCopyFromSrc(cmd byte) bool {
- return (cmd & 0x80) != 0
+ return (cmd & continuation) != 0
}
func isCopyFromDelta(cmd byte) bool {
- return (cmd&0x80) == 0 && cmd != 0
+ return (cmd&continuation) == 0 && cmd != 0
}
func decodeOffsetByteReader(cmd byte, delta io.ByteReader) (uint, error) {
var offset uint
- if (cmd & 0x01) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
- }
- offset = uint(next)
- }
- if (cmd & 0x02) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
- }
- offset |= uint(next) << 8
- }
- if (cmd & 0x04) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
- }
- offset |= uint(next) << 16
- }
- if (cmd & 0x08) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
+ for _, o := range offsets {
+ if (cmd & o.mask) != 0 {
+ next, err := delta.ReadByte()
+ if err != nil {
+ return 0, err
+ }
+ offset |= uint(next) << o.shift
}
- offset |= uint(next) << 24
}
return offset, nil
@@ -457,33 +462,14 @@ func decodeOffsetByteReader(cmd byte, delta io.ByteReader) (uint, error) {
func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) {
var offset uint
- if (cmd & 0x01) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
- }
- offset = uint(delta[0])
- delta = delta[1:]
- }
- if (cmd & 0x02) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
- }
- offset |= uint(delta[0]) << 8
- delta = delta[1:]
- }
- if (cmd & 0x04) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
- }
- offset |= uint(delta[0]) << 16
- delta = delta[1:]
- }
- if (cmd & 0x08) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
+ for _, o := range offsets {
+ if (cmd & o.mask) != 0 {
+ if len(delta) == 0 {
+ return 0, nil, ErrInvalidDelta
+ }
+ offset |= uint(delta[0]) << o.shift
+ delta = delta[1:]
}
- offset |= uint(delta[0]) << 24
- delta = delta[1:]
}
return offset, delta, nil
@@ -491,29 +477,18 @@ func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) {
func decodeSizeByteReader(cmd byte, delta io.ByteReader) (uint, error) {
var sz uint
- if (cmd & 0x10) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
- }
- sz = uint(next)
- }
- if (cmd & 0x20) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
- }
- sz |= uint(next) << 8
- }
- if (cmd & 0x40) != 0 {
- next, err := delta.ReadByte()
- if err != nil {
- return 0, err
+ for _, s := range sizes {
+ if (cmd & s.mask) != 0 {
+ next, err := delta.ReadByte()
+ if err != nil {
+ return 0, err
+ }
+ sz |= uint(next) << s.shift
}
- sz |= uint(next) << 16
}
+
if sz == 0 {
- sz = 0x10000
+ sz = maxCopySize
}
return sz, nil
@@ -521,29 +496,17 @@ func decodeSizeByteReader(cmd byte, delta io.ByteReader) (uint, error) {
func decodeSize(cmd byte, delta []byte) (uint, []byte, error) {
var sz uint
- if (cmd & 0x10) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
- }
- sz = uint(delta[0])
- delta = delta[1:]
- }
- if (cmd & 0x20) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
- }
- sz |= uint(delta[0]) << 8
- delta = delta[1:]
- }
- if (cmd & 0x40) != 0 {
- if len(delta) == 0 {
- return 0, nil, ErrInvalidDelta
+ for _, s := range sizes {
+ if (cmd & s.mask) != 0 {
+ if len(delta) == 0 {
+ return 0, nil, ErrInvalidDelta
+ }
+ sz |= uint(delta[0]) << s.shift
+ delta = delta[1:]
}
- sz |= uint(delta[0]) << 16
- delta = delta[1:]
}
if sz == 0 {
- sz = 0x10000
+ sz = maxCopySize
}
return sz, delta, nil