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// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package safe
import (
"errors"
"io/ioutil"
"os"
"path/filepath"
)
// File represents safe file descriptor.
type File struct {
name string
tmpfile *os.File
closed bool
aborted bool
}
// Write writes len(b) bytes to the temporary File. In case of error, the temporary file is removed.
func (file *File) Write(b []byte) (n int, err error) {
if file.closed {
err = errors.New("write on closed file")
return
}
if file.aborted {
err = errors.New("write on aborted file")
return
}
defer func() {
if err != nil {
os.Remove(file.tmpfile.Name())
file.aborted = true
}
}()
n, err = file.tmpfile.Write(b)
return
}
// Close closes the temporary File and renames to the named file. In case of error, the temporary file is removed.
func (file *File) Close() (err error) {
defer func() {
if err != nil {
os.Remove(file.tmpfile.Name())
file.aborted = true
}
}()
if file.closed {
err = errors.New("close on closed file")
return
}
if file.aborted {
err = errors.New("close on aborted file")
return
}
if err = file.tmpfile.Close(); err != nil {
return
}
err = os.Rename(file.tmpfile.Name(), file.name)
file.closed = true
return
}
// Abort aborts the temporary File by closing and removing the temporary file.
func (file *File) Abort() (err error) {
if file.closed {
err = errors.New("abort on closed file")
return
}
if file.aborted {
err = errors.New("abort on aborted file")
return
}
file.tmpfile.Close()
err = os.Remove(file.tmpfile.Name())
file.aborted = true
return
}
// CreateFile creates the named file safely from unique temporary file.
// The temporary file is renamed to the named file upon successful close
// to safeguard intermediate state in the named file. The temporary file
// is created in the name of the named file with suffixed unique number
// and prefixed "$tmpfile" string. While creating the temporary file,
// missing parent directories are also created. The temporary file is
// removed if case of any intermediate failure. Not removed temporary
// files can be cleaned up by identifying them using "$tmpfile" prefix
// string.
func CreateFile(name string) (*File, error) {
// ioutil.TempFile() fails if parent directory is missing.
// Create parent directory to avoid such error.
dname := filepath.Dir(name)
if err := os.MkdirAll(dname, 0o700); err != nil {
return nil, err
}
fname := filepath.Base(name)
tmpfile, err := ioutil.TempFile(dname, "$tmpfile."+fname+".")
if err != nil {
return nil, err
}
if err = os.Chmod(tmpfile.Name(), 0o600); err != nil {
if rerr := os.Remove(tmpfile.Name()); rerr != nil {
err = rerr
}
return nil, err
}
return &File{name: name, tmpfile: tmpfile}, nil
}
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