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minio/pkg/safe/safe.go

130 lines
3.6 KiB

/*
* Minio Cloud Storage (C) 2015-2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// NOTE - Rename() not guaranteed to be safe on all filesystems which are not fully POSIX compatible
// Package safe provides safe file write semantics by leveraging Rename's() safeity.
package safe
import (
"io"
"io/ioutil"
"os"
"path/filepath"
)
// Vault - vault is an interface for different implementations of safe
// i/o semantics.
type Vault interface {
io.ReadWriteCloser
SyncClose() error
CloseAndRemove() error
}
// File provides for safe file writes.
type File struct {
*os.File
file string
}
// SyncClose sync file to disk and close, returns an error if any
func (f *File) SyncClose() error {
// sync to the disk
if err := f.File.Sync(); err != nil {
return err
}
// Close the fd.
if err := f.Close(); err != nil {
return err
}
return nil
}
// Close the file, returns an error if any
func (f *File) Close() error {
// Close the embedded fd.
if err := f.File.Close(); err != nil {
return err
}
// Safe rename to final destination
if err := os.Rename(f.Name(), f.file); err != nil {
return err
}
return nil
}
// CloseAndRemove closes the temp file, and safely removes it. Returns
// error if any.
func (f *File) CloseAndRemove() error {
// close the embedded fd
f.File.Close()
// Remove the temp file.
if err := os.Remove(f.Name()); err != nil {
return err
}
return nil
}
// CreateFile creates a new file at filePath for safe writes, it also
// creates parent directories if they don't exist.
func CreateFile(filePath string) (*File, error) {
return CreateFileWithPrefix(filePath, "$deleteme.")
}
// CreateFileWithSuffix is similar to CreateFileWithPrefix, but the
// second argument is treated as suffix for the temporary files.
func CreateFileWithSuffix(filePath string, suffix string) (*File, error) {
// If parent directories do not exist, ioutil.TempFile doesn't create them
// handle such a case with os.MkdirAll()
if err := os.MkdirAll(filepath.Dir(filePath), 0700); err != nil {
return nil, err
}
f, err := ioutil.TempFile(filepath.Dir(filePath), filepath.Base(filePath)+suffix)
if err != nil {
return nil, err
}
if err = os.Chmod(f.Name(), 0600); err != nil {
if err = os.Remove(f.Name()); err != nil {
return nil, err
}
return nil, err
}
return &File{File: f, file: filePath}, nil
}
// CreateFileWithPrefix creates a new file at filePath for safe
// writes, it also creates parent directories if they don't exist.
// prefix specifies the prefix of the temporary files so that cleaning
// stale temp files is easy.
func CreateFileWithPrefix(filePath string, prefix string) (*File, error) {
// If parent directories do not exist, ioutil.TempFile doesn't create them
// handle such a case with os.MkdirAll()
if err := os.MkdirAll(filepath.Dir(filePath), 0700); err != nil {
return nil, err
}
f, err := ioutil.TempFile(filepath.Dir(filePath), prefix+filepath.Base(filePath))
if err != nil {
return nil, err
}
if err = os.Chmod(f.Name(), 0600); err != nil {
if err = os.Remove(f.Name()); err != nil {
return nil, err
}
return nil, err
}
return &File{File: f, file: filePath}, nil
}