mirror of
https://github.com/go-gitea/gitea
synced 2024-11-09 11:44:27 +00:00
276 lines
7.4 KiB
Go
276 lines
7.4 KiB
Go
// Copyright 2020 The Gitea Authors. All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package git
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import (
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"bufio"
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"bytes"
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"io"
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"math"
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"strconv"
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"strings"
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)
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// CatFileBatch opens git cat-file --batch in the provided repo and returns a stdin pipe, a stdout reader and cancel function
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func CatFileBatch(repoPath string) (*io.PipeWriter, *bufio.Reader, func()) {
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// Next feed the commits in order into cat-file --batch, followed by their trees and sub trees as necessary.
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// so let's create a batch stdin and stdout
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batchStdinReader, batchStdinWriter := io.Pipe()
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batchStdoutReader, batchStdoutWriter := io.Pipe()
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cancel := func() {
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_ = batchStdinReader.Close()
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_ = batchStdinWriter.Close()
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_ = batchStdoutReader.Close()
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_ = batchStdoutWriter.Close()
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}
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go func() {
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stderr := strings.Builder{}
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err := NewCommand("cat-file", "--batch").RunInDirFullPipeline(repoPath, batchStdoutWriter, &stderr, batchStdinReader)
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if err != nil {
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_ = batchStdoutWriter.CloseWithError(ConcatenateError(err, (&stderr).String()))
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_ = batchStdinReader.CloseWithError(ConcatenateError(err, (&stderr).String()))
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} else {
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_ = batchStdoutWriter.Close()
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_ = batchStdinReader.Close()
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}
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}()
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// For simplicities sake we'll us a buffered reader to read from the cat-file --batch
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batchReader := bufio.NewReader(batchStdoutReader)
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return batchStdinWriter, batchReader, cancel
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}
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// ReadBatchLine reads the header line from cat-file --batch
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// We expect:
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// <sha> SP <type> SP <size> LF
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func ReadBatchLine(rd *bufio.Reader) (sha []byte, typ string, size int64, err error) {
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sha, err = rd.ReadBytes(' ')
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if err != nil {
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return
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}
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sha = sha[:len(sha)-1]
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typ, err = rd.ReadString(' ')
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if err != nil {
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return
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}
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typ = typ[:len(typ)-1]
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var sizeStr string
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sizeStr, err = rd.ReadString('\n')
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if err != nil {
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return
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}
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size, err = strconv.ParseInt(sizeStr[:len(sizeStr)-1], 10, 64)
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return
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}
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// ReadTagObjectID reads a tag object ID hash from a cat-file --batch stream, throwing away the rest of the stream.
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func ReadTagObjectID(rd *bufio.Reader, size int64) (string, error) {
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id := ""
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var n int64
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headerLoop:
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for {
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line, err := rd.ReadBytes('\n')
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if err != nil {
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return "", err
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}
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n += int64(len(line))
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idx := bytes.Index(line, []byte{' '})
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if idx < 0 {
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continue
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}
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if string(line[:idx]) == "object" {
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id = string(line[idx+1 : len(line)-1])
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break headerLoop
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}
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}
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// Discard the rest of the tag
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discard := size - n
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for discard > math.MaxInt32 {
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_, err := rd.Discard(math.MaxInt32)
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if err != nil {
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return id, err
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}
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discard -= math.MaxInt32
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}
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_, err := rd.Discard(int(discard))
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return id, err
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}
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// ReadTreeID reads a tree ID from a cat-file --batch stream, throwing away the rest of the stream.
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func ReadTreeID(rd *bufio.Reader, size int64) (string, error) {
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id := ""
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var n int64
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headerLoop:
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for {
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line, err := rd.ReadBytes('\n')
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if err != nil {
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return "", err
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}
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n += int64(len(line))
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idx := bytes.Index(line, []byte{' '})
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if idx < 0 {
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continue
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}
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if string(line[:idx]) == "tree" {
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id = string(line[idx+1 : len(line)-1])
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break headerLoop
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}
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}
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// Discard the rest of the commit
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discard := size - n
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for discard > math.MaxInt32 {
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_, err := rd.Discard(math.MaxInt32)
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if err != nil {
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return id, err
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}
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discard -= math.MaxInt32
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}
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_, err := rd.Discard(int(discard))
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return id, err
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}
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// git tree files are a list:
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// <mode-in-ascii> SP <fname> NUL <20-byte SHA>
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//
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// Unfortunately this 20-byte notation is somewhat in conflict to all other git tools
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// Therefore we need some method to convert these 20-byte SHAs to a 40-byte SHA
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// constant hextable to help quickly convert between 20byte and 40byte hashes
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const hextable = "0123456789abcdef"
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// To40ByteSHA converts a 20-byte SHA into a 40-byte sha. Input and output can be the
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// same 40 byte slice to support in place conversion without allocations.
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// This is at least 100x quicker that hex.EncodeToString
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// NB This requires that out is a 40-byte slice
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func To40ByteSHA(sha, out []byte) []byte {
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for i := 19; i >= 0; i-- {
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v := sha[i]
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vhi, vlo := v>>4, v&0x0f
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shi, slo := hextable[vhi], hextable[vlo]
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out[i*2], out[i*2+1] = shi, slo
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}
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return out
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}
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// ParseTreeLineSkipMode reads an entry from a tree in a cat-file --batch stream
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// This simply skips the mode - saving a substantial amount of time and carefully avoids allocations - except where fnameBuf is too small.
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// It is recommended therefore to pass in an fnameBuf large enough to avoid almost all allocations
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//
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// Each line is composed of:
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// <mode-in-ascii-dropping-initial-zeros> SP <fname> NUL <20-byte SHA>
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//
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// We don't attempt to convert the 20-byte SHA to 40-byte SHA to save a lot of time
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func ParseTreeLineSkipMode(rd *bufio.Reader, fnameBuf, shaBuf []byte) (fname, sha []byte, n int, err error) {
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var readBytes []byte
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// Skip the Mode
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readBytes, err = rd.ReadSlice(' ') // NB: DOES NOT ALLOCATE SIMPLY RETURNS SLICE WITHIN READER BUFFER
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if err != nil {
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return
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}
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n += len(readBytes)
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// Deal with the fname
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readBytes, err = rd.ReadSlice('\x00')
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copy(fnameBuf, readBytes)
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if len(fnameBuf) > len(readBytes) {
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fnameBuf = fnameBuf[:len(readBytes)] // cut the buf the correct size
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} else {
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fnameBuf = append(fnameBuf, readBytes[len(fnameBuf):]...) // extend the buf and copy in the missing bits
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}
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for err == bufio.ErrBufferFull { // Then we need to read more
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readBytes, err = rd.ReadSlice('\x00')
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fnameBuf = append(fnameBuf, readBytes...) // there is little point attempting to avoid allocations here so just extend
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}
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n += len(fnameBuf)
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if err != nil {
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return
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}
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fnameBuf = fnameBuf[:len(fnameBuf)-1] // Drop the terminal NUL
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fname = fnameBuf // set the returnable fname to the slice
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// Now deal with the 20-byte SHA
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idx := 0
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for idx < 20 {
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read := 0
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read, err = rd.Read(shaBuf[idx:20])
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n += read
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if err != nil {
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return
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}
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idx += read
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}
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sha = shaBuf
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return
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}
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// ParseTreeLine reads an entry from a tree in a cat-file --batch stream
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// This carefully avoids allocations - except where fnameBuf is too small.
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// It is recommended therefore to pass in an fnameBuf large enough to avoid almost all allocations
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//
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// Each line is composed of:
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// <mode-in-ascii-dropping-initial-zeros> SP <fname> NUL <20-byte SHA>
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//
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// We don't attempt to convert the 20-byte SHA to 40-byte SHA to save a lot of time
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func ParseTreeLine(rd *bufio.Reader, modeBuf, fnameBuf, shaBuf []byte) (mode, fname, sha []byte, n int, err error) {
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var readBytes []byte
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// Read the Mode
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readBytes, err = rd.ReadSlice(' ')
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if err != nil {
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return
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}
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n += len(readBytes)
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copy(modeBuf, readBytes)
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if len(modeBuf) > len(readBytes) {
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modeBuf = modeBuf[:len(readBytes)]
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} else {
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modeBuf = append(modeBuf, readBytes[len(modeBuf):]...)
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}
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mode = modeBuf[:len(modeBuf)-1] // Drop the SP
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// Deal with the fname
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readBytes, err = rd.ReadSlice('\x00')
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copy(fnameBuf, readBytes)
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if len(fnameBuf) > len(readBytes) {
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fnameBuf = fnameBuf[:len(readBytes)]
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} else {
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fnameBuf = append(fnameBuf, readBytes[len(fnameBuf):]...)
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}
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for err == bufio.ErrBufferFull {
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readBytes, err = rd.ReadSlice('\x00')
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fnameBuf = append(fnameBuf, readBytes...)
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}
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n += len(fnameBuf)
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if err != nil {
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return
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}
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fnameBuf = fnameBuf[:len(fnameBuf)-1]
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fname = fnameBuf
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// Deal with the 20-byte SHA
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idx := 0
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for idx < 20 {
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read := 0
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read, err = rd.Read(shaBuf[idx:20])
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n += read
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if err != nil {
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return
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}
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idx += read
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}
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sha = shaBuf
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return
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}
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