+++ /dev/null
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package cache
-
-import (
- "bytes"
- "crypto/sha256"
- "fmt"
- "hash"
- "io"
- "os"
- "sync"
-)
-
-var debugHash = false // set when GODEBUG=gocachehash=1
-
-// HashSize is the number of bytes in a hash.
-const HashSize = 32
-
-// A Hash provides access to the canonical hash function used to index the cache.
-// The current implementation uses salted SHA256, but clients must not assume this.
-type Hash struct {
- h hash.Hash
- name string // for debugging
- buf *bytes.Buffer // for verify
-}
-
-// hashSalt is a salt string added to the beginning of every hash
-// created by NewHash. Using the Staticcheck version makes sure that different
-// versions of the command do not address the same cache
-// entries, so that a bug in one version does not affect the execution
-// of other versions. This salt will result in additional ActionID files
-// in the cache, but not additional copies of the large output files,
-// which are still addressed by unsalted SHA256.
-var hashSalt []byte
-
-func SetSalt(b []byte) {
- hashSalt = b
-}
-
-// Subkey returns an action ID corresponding to mixing a parent
-// action ID with a string description of the subkey.
-func Subkey(parent ActionID, desc string) ActionID {
- h := sha256.New()
- h.Write([]byte("subkey:"))
- h.Write(parent[:])
- h.Write([]byte(desc))
- var out ActionID
- h.Sum(out[:0])
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH subkey %x %q = %x\n", parent, desc, out)
- }
- if verify {
- hashDebug.Lock()
- hashDebug.m[out] = fmt.Sprintf("subkey %x %q", parent, desc)
- hashDebug.Unlock()
- }
- return out
-}
-
-// NewHash returns a new Hash.
-// The caller is expected to Write data to it and then call Sum.
-func NewHash(name string) *Hash {
- h := &Hash{h: sha256.New(), name: name}
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH[%s]\n", h.name)
- }
- h.Write(hashSalt)
- if verify {
- h.buf = new(bytes.Buffer)
- }
- return h
-}
-
-// Write writes data to the running hash.
-func (h *Hash) Write(b []byte) (int, error) {
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH[%s]: %q\n", h.name, b)
- }
- if h.buf != nil {
- h.buf.Write(b)
- }
- return h.h.Write(b)
-}
-
-// Sum returns the hash of the data written previously.
-func (h *Hash) Sum() [HashSize]byte {
- var out [HashSize]byte
- h.h.Sum(out[:0])
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH[%s]: %x\n", h.name, out)
- }
- if h.buf != nil {
- hashDebug.Lock()
- if hashDebug.m == nil {
- hashDebug.m = make(map[[HashSize]byte]string)
- }
- hashDebug.m[out] = h.buf.String()
- hashDebug.Unlock()
- }
- return out
-}
-
-// In GODEBUG=gocacheverify=1 mode,
-// hashDebug holds the input to every computed hash ID,
-// so that we can work backward from the ID involved in a
-// cache entry mismatch to a description of what should be there.
-var hashDebug struct {
- sync.Mutex
- m map[[HashSize]byte]string
-}
-
-// reverseHash returns the input used to compute the hash id.
-func reverseHash(id [HashSize]byte) string {
- hashDebug.Lock()
- s := hashDebug.m[id]
- hashDebug.Unlock()
- return s
-}
-
-var hashFileCache struct {
- sync.Mutex
- m map[string][HashSize]byte
-}
-
-// FileHash returns the hash of the named file.
-// It caches repeated lookups for a given file,
-// and the cache entry for a file can be initialized
-// using SetFileHash.
-// The hash used by FileHash is not the same as
-// the hash used by NewHash.
-func FileHash(file string) ([HashSize]byte, error) {
- hashFileCache.Lock()
- out, ok := hashFileCache.m[file]
- hashFileCache.Unlock()
-
- if ok {
- return out, nil
- }
-
- h := sha256.New()
- f, err := os.Open(file)
- if err != nil {
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH %s: %v\n", file, err)
- }
- return [HashSize]byte{}, err
- }
- _, err = io.Copy(h, f)
- f.Close()
- if err != nil {
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH %s: %v\n", file, err)
- }
- return [HashSize]byte{}, err
- }
- h.Sum(out[:0])
- if debugHash {
- fmt.Fprintf(os.Stderr, "HASH %s: %x\n", file, out)
- }
-
- SetFileHash(file, out)
- return out, nil
-}
-
-// SetFileHash sets the hash returned by FileHash for file.
-func SetFileHash(file string, sum [HashSize]byte) {
- hashFileCache.Lock()
- if hashFileCache.m == nil {
- hashFileCache.m = make(map[string][HashSize]byte)
- }
- hashFileCache.m[file] = sum
- hashFileCache.Unlock()
-}
projects / dotfiles / .git / blobdiff