mirror of
https://github.com/golang/go
synced 2024-11-06 08:26:12 -07:00
55402a2b46
This isn't exposed through the godoc binary, as it will only be used by the Google-specific deployment of godoc. Change-Id: Id5808f3adcb7eb36a7ccd6e4960ce3f01179fe51 Reviewed-on: https://go-review.googlesource.com/1567 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
139 lines
2.9 KiB
Go
139 lines
2.9 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file provides a compact encoding of
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// a map of Mercurial hashes to Git hashes.
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package redirect
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import (
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"encoding/binary"
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"fmt"
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"io"
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"os"
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"sort"
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"strconv"
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"strings"
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)
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// hashMap is a map of Mercurial hashes to Git hashes.
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type hashMap struct {
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file *os.File
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entries int
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}
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// newHashMap takes a file handle that contains a map of Mercurial to Git
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// hashes. The file should be a sequence of pairs of little-endian encoded
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// uint32s, representing a hgHash and a gitHash respectively.
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// The sequence must be sorted by hgHash.
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// The file must remain open for as long as the returned hashMap is used.
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func newHashMap(f *os.File) (*hashMap, error) {
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fi, err := f.Stat()
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if err != nil {
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return nil, err
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}
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return &hashMap{file: f, entries: int(fi.Size() / 8)}, nil
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}
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// Lookup finds an hgHash in the map that matches the given prefix, and returns
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// its corresponding gitHash. The prefix must be at least 8 characters long.
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func (m *hashMap) Lookup(s string) gitHash {
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if m == nil {
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return 0
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}
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hg, err := hgHashFromString(s)
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if err != nil {
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return 0
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}
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var git gitHash
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b := make([]byte, 8)
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sort.Search(m.entries, func(i int) bool {
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n, err := m.file.ReadAt(b, int64(i*8))
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if err != nil {
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panic(err)
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}
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if n != 8 {
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panic(io.ErrUnexpectedEOF)
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}
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v := hgHash(binary.LittleEndian.Uint32(b[:4]))
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if v == hg {
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git = gitHash(binary.LittleEndian.Uint32(b[4:]))
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}
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return v >= hg
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})
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return git
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}
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// hgHash represents the lower (leftmost) 32 bits of a Mercurial hash.
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type hgHash uint32
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func (h hgHash) String() string {
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return intToHash(int64(h))
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}
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func hgHashFromString(s string) (hgHash, error) {
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if len(s) < 8 {
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return 0, fmt.Errorf("string too small: len(s) = %d", len(s))
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}
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hash := s[:8]
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i, err := strconv.ParseInt(hash, 16, 64)
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if err != nil {
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return 0, err
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}
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return hgHash(i), nil
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}
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// gitHash represents the leftmost 28 bits of a Git hash in its upper 28 bits,
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// and it encodes hash's repository in the lower 4 bits.
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type gitHash uint32
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func (h gitHash) Hash() string {
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return intToHash(int64(h))[:7]
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}
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func (h gitHash) Repo() string {
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return repo(h & 0xF).String()
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}
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func intToHash(i int64) string {
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s := strconv.FormatInt(i, 16)
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if len(s) < 8 {
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s = strings.Repeat("0", 8-len(s)) + s
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}
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return s
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}
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// repo represents a Go Git repository.
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type repo byte
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const (
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repoGo repo = iota
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repoBlog
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repoCrypto
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repoExp
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repoImage
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repoMobile
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repoNet
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repoSys
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repoTalks
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repoText
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repoTools
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)
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func (r repo) String() string {
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return map[repo]string{
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repoGo: "go",
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repoBlog: "blog",
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repoCrypto: "crypto",
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repoExp: "exp",
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repoImage: "image",
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repoMobile: "mobile",
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repoNet: "net",
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repoSys: "sys",
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repoTalks: "talks",
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repoText: "text",
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repoTools: "tools",
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}[r]
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}
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