1 files changed, 176 insertions, 0 deletions

diff --git a/vendor/honnef.co/go/tools/internal/cache/hash.go b/vendor/honnef.co/go/tools/internal/cache/hash.go
new file mode 100644
index 0000000..a53543e
--- /dev/null
+++ b/vendor/honnef.co/go/tools/internal/cache/hash.go
@@ -0,0 +1,176 @@
+// 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()
+}