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Abstract hash function usage (#28138)

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Refactor Hash interfaces and centralize hash function. This will allow
easier introduction of different hash function later on.

This forms the "no-op" part of the SHA256 enablement patch.
This commit is contained in:
Adam Majer 2023-12-13 21:02:00 +00:00 • committed by GitHub
parent 064f05204c
commit cbf923e87b
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122 changed files with 947 additions and 594 deletions
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30
modules/git/batch_reader.go
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@ -148,7 +148,7 @@ func CatFileBatch(ctx context.Context, repoPath string) (WriteCloserError, *bufi
// ReadBatchLine reads the header line from cat-file --batch
// We expect:
// <sha> SP <type> SP <size> LF
// sha is a 40byte not 20byte here
// sha is a hex encoded here
func ReadBatchLine(rd *bufio.Reader) (sha []byte, typ string, size int64, err error) {
typ, err = rd.ReadString('\n')
if err != nil {
@ -251,20 +251,19 @@ headerLoop:
}
// git tree files are a list:
// <mode-in-ascii> SP <fname> NUL <20-byte SHA>
// <mode-in-ascii> SP <fname> NUL <binary Hash>
//
// Unfortunately this 20-byte notation is somewhat in conflict to all other git tools
// Therefore we need some method to convert these 20-byte SHAs to a 40-byte SHA
// Therefore we need some method to convert these binary hashes to hex hashes
// constant hextable to help quickly convert between 20byte and 40byte hashes
// constant hextable to help quickly convert between binary and hex representation
const hextable = "0123456789abcdef"
// To40ByteSHA converts a 20-byte SHA into a 40-byte sha. Input and output can be the
// same 40 byte slice to support in place conversion without allocations.
// BinToHexHeash converts a binary Hash into a hex encoded one. Input and output can be the
// same byte slice to support in place conversion without allocations.
// This is at least 100x quicker that hex.EncodeToString
// NB This requires that out is a 40-byte slice
func To40ByteSHA(sha, out []byte) []byte {
for i := 19; i >= 0; i-- {
func BinToHex(objectFormat ObjectFormat, sha, out []byte) []byte {
for i := objectFormat.FullLength()/2 - 1; i >= 0; i-- {
v := sha[i]
vhi, vlo := v>>4, v&0x0f
shi, slo := hextable[vhi], hextable[vlo]
@ -278,10 +277,10 @@ func To40ByteSHA(sha, out []byte) []byte {
// It is recommended therefore to pass in an fnameBuf large enough to avoid almost all allocations
//
// Each line is composed of:
// <mode-in-ascii-dropping-initial-zeros> SP <fname> NUL <20-byte SHA>
// <mode-in-ascii-dropping-initial-zeros> SP <fname> NUL <binary HASH>
//
// We don't attempt to convert the 20-byte SHA to 40-byte SHA to save a lot of time
func ParseTreeLine(rd *bufio.Reader, modeBuf, fnameBuf, shaBuf []byte) (mode, fname, sha []byte, n int, err error) {
// We don't attempt to convert the raw HASH to save a lot of time
func ParseTreeLine(objectFormat ObjectFormat, rd *bufio.Reader, modeBuf, fnameBuf, shaBuf []byte) (mode, fname, sha []byte, n int, err error) {
var readBytes []byte
// Read the Mode & fname
@ -324,11 +323,12 @@ func ParseTreeLine(rd *bufio.Reader, modeBuf, fnameBuf, shaBuf []byte) (mode, fn
fnameBuf = fnameBuf[:len(fnameBuf)-1]
fname = fnameBuf
// Deal with the 20-byte SHA
// Deal with the binary hash
idx = 0
for idx < 20 {
len := objectFormat.FullLength() / 2
for idx < len {
var read int
read, err = rd.Read(shaBuf[idx:20])
read, err = rd.Read(shaBuf[idx:len])
n += read
if err != nil {
return mode, fname, sha, n, err