Update generated and dep addition of safefile

vendor/github.com/dchest/safefile/safefile.go

@@ -0,0 +1,197 @@
+// Copyright 2013 Dmitry Chestnykh. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package safefile implements safe "atomic" saving of files.
+//
+// Instead of truncating and overwriting the destination file, it creates a
+// temporary file in the same directory, writes to it, and then renames the
+// temporary file to the original name when calling Commit.
+//
+// Example:
+//
+//  f, err := safefile.Create("/home/ken/report.txt", 0644)
+//  if err != nil {
+//  	// ...
+//  }
+//  // Created temporary file /home/ken/sf-ppcyksu5hyw2mfec.tmp
+//
+//  defer f.Close()
+//
+//  _, err = io.WriteString(f, "Hello world")
+//  if err != nil {
+//  	// ...
+//  }
+//  // Wrote "Hello world" to /home/ken/sf-ppcyksu5hyw2mfec.tmp
+//
+//  err = f.Commit()
+//  if err != nil {
+//      // ...
+//  }
+//  // Renamed /home/ken/sf-ppcyksu5hyw2mfec.tmp to /home/ken/report.txt
+//
+package safefile
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// ErrAlreadyCommitted error is returned when calling Commit on a file that
+// has been already successfully committed.
+var ErrAlreadyCommitted = errors.New("file already committed")
+
+type File struct {
+	*os.File
+	origName    string
+	closeFunc   func(*File) error
+	isClosed    bool // if true, temporary file has been closed, but not renamed
+	isCommitted bool // if true, the file has been successfully committed
+}
+
+func makeTempName(origname, prefix string) (tempname string, err error) {
+	origname = filepath.Clean(origname)
+	if len(origname) == 0 || origname[len(origname)-1] == filepath.Separator {
+		return "", os.ErrInvalid
+	}
+	// Generate 10 random bytes.
+	// This gives 80 bits of entropy, good enough
+	// for making temporary file name unpredictable.
+	var rnd [10]byte
+	if _, err := rand.Read(rnd[:]); err != nil {
+		return "", err
+	}
+	name := prefix + "-" + strings.ToLower(base32.StdEncoding.EncodeToString(rnd[:])) + ".tmp"
+	return filepath.Join(filepath.Dir(origname), name), nil
+}
+
+// Create creates a temporary file in the same directory as filename,
+// which will be renamed to the given filename when calling Commit.
+func Create(filename string, perm os.FileMode) (*File, error) {
+	for {
+		tempname, err := makeTempName(filename, "sf")
+		if err != nil {
+			return nil, err
+		}
+		f, err := os.OpenFile(tempname, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
+		if err != nil {
+			if os.IsExist(err) {
+				continue
+			}
+			return nil, err
+		}
+		return &File{
+			File:      f,
+			origName:  filename,
+			closeFunc: closeUncommitted,
+		}, nil
+	}
+}
+
+// OrigName returns the original filename given to Create.
+func (f *File) OrigName() string {
+	return f.origName
+}
+
+// Close closes temporary file and removes it.
+// If the file has been committed, Close is no-op.
+func (f *File) Close() error {
+	return f.closeFunc(f)
+}
+
+func closeUncommitted(f *File) error {
+	err0 := f.File.Close()
+	err1 := os.Remove(f.Name())
+	f.closeFunc = closeAgainError
+	if err0 != nil {
+		return err0
+	}
+	return err1
+}
+
+func closeAfterFailedRename(f *File) error {
+	// Remove temporary file.
+	//
+	// The note from Commit function applies here too, as we may be
+	// removing a different file. However, since we rely on our temporary
+	// names being unpredictable, this should not be a concern.
+	f.closeFunc = closeAgainError
+	return os.Remove(f.Name())
+}
+
+func closeCommitted(f *File) error {
+	// noop
+	return nil
+}
+
+func closeAgainError(f *File) error {
+	return os.ErrInvalid
+}
+
+// Commit safely commits data into the original file by syncing temporary
+// file to disk, closing it and renaming to the original file name.
+//
+// In case of success, the temporary file is closed and no longer exists
+// on disk. It is safe to call Close after Commit: the operation will do
+// nothing.
+//
+// In case of error, the temporary file is still opened and exists on disk;
+// it must be closed by callers by calling Close or by trying to commit again.
+
+// Note that when trying to Commit again after a failed Commit when the file
+// has been closed, but not renamed to its original name (the new commit will
+// try again to rename it), safefile cannot guarantee that the temporary file
+// has not been changed, or that it is the same temporary file we were dealing
+// with.  However, since the temporary name is unpredictable, it is unlikely
+// that this happened accidentally. If complete atomicity is needed, do not
+// Commit again after error, write the file again.
+func (f *File) Commit() error {
+	if f.isCommitted {
+		return ErrAlreadyCommitted
+	}
+	if !f.isClosed {
+		// Sync to disk.
+		err := f.Sync()
+		if err != nil {
+			return err
+		}
+		// Close underlying os.File.
+		err = f.File.Close()
+		if err != nil {
+			return err
+		}
+		f.isClosed = true
+	}
+	// Rename.
+	err := rename(f.Name(), f.origName)
+	if err != nil {
+		f.closeFunc = closeAfterFailedRename
+		return err
+	}
+	f.closeFunc = closeCommitted
+	f.isCommitted = true
+	return nil
+}
+
+// WriteFile is a safe analog of ioutil.WriteFile.
+func WriteFile(filename string, data []byte, perm os.FileMode) error {
+	f, err := Create(filename, perm)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	n, err := f.Write(data)
+	if err != nil {
+		return err
+	}
+	if err == nil && n < len(data) {
+		err = io.ErrShortWrite
+		return err
+	}
+	return f.Commit()
+}