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minio/pkg/atomic/atomic.go

95 lines
2.8 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 atomic on all filesystems which are not fully POSIX compatible
// Package atomic provides atomic file write semantics by leveraging Rename's() atomicity.
package atomic
import (
"io/ioutil"
"os"
"path/filepath"
)
// File container provided for atomic file writes
type File struct {
*os.File
file string
}
// CloseAndSync sync file to disk and close, returns an error if any
func (f *File) CloseAndSync() error {
// sync to the disk
if err := f.File.Sync(); err != nil {
return err
}
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
}
// atomic rename to final destination
if err := os.Rename(f.Name(), f.file); err != nil {
return err
}
return nil
}
// CloseAndPurge removes the temp file, closes the transaction and returns an error if any
func (f *File) CloseAndPurge() error {
// close the embedded fd
if err := f.File.Close(); err != nil {
return err
}
if err := os.Remove(f.Name()); err != nil {
return err
}
return nil
}
// FileCreate creates a new file at filePath for atomic writes, it also creates parent directories if they don't exist
func FileCreate(filePath string) (*File, error) {
return FileCreateWithPrefix(filePath, "$deleteme.")
}
// FileCreateWithPrefix creates a new file at filePath for atomic 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 FileCreateWithPrefix(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
}