From 73df946d56c74384511a194dd01dbe099584fd1a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 15:14:23 +0200 Subject: Adding upstream version 1.16.10. Signed-off-by: Daniel Baumann --- src/cmd/go/internal/cache/hash.go | 174 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 174 insertions(+) create mode 100644 src/cmd/go/internal/cache/hash.go (limited to 'src/cmd/go/internal/cache/hash.go') diff --git a/src/cmd/go/internal/cache/hash.go b/src/cmd/go/internal/cache/hash.go new file mode 100644 index 0000000..e4bb2a3 --- /dev/null +++ b/src/cmd/go/internal/cache/hash.go @@ -0,0 +1,174 @@ +// 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" + "runtime" + "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 Go version makes sure that different +// versions of the go command (or even different Git commits during +// work on the development branch) 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(runtime.Version()) + +// 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() +} -- cgit v1.2.3