mirror of https://github.com/hashicorp/consul
124 lines
2.5 KiB
Go
124 lines
2.5 KiB
Go
package safeio
|
|
|
|
import (
|
|
"errors"
|
|
"io/ioutil"
|
|
"os"
|
|
"path/filepath"
|
|
)
|
|
|
|
var errClosed = errors.New("file is already closed")
|
|
|
|
// OpenFile is the incremental version of WriteToFile. It opens a temp
|
|
// file and proxies writes through to the underlying file.
|
|
//
|
|
// If Close is called before Commit, the temp file is closed and erased.
|
|
//
|
|
// If Commit is called before Close, the temp file is closed, fsynced,
|
|
// and atomically renamed to the desired final name.
|
|
func OpenFile(path string, perm os.FileMode) (*File, error) {
|
|
dir := filepath.Dir(path)
|
|
name := filepath.Base(path)
|
|
|
|
f, err := ioutil.TempFile(dir, name+".tmp")
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &File{
|
|
name: path,
|
|
tempName: f.Name(),
|
|
perm: perm,
|
|
file: f,
|
|
}, nil
|
|
}
|
|
|
|
// File is an implementation detail of OpenFile.
|
|
type File struct {
|
|
name string // track desired filename
|
|
tempName string // track actual filename
|
|
perm os.FileMode
|
|
file *os.File
|
|
closed bool
|
|
err error // the first error encountered
|
|
}
|
|
|
|
// Write is a thin proxy to *os.File#Write.
|
|
//
|
|
// If Close or Commit were called, this immediately exits with an error.
|
|
func (f *File) Write(p []byte) (n int, err error) {
|
|
if f.closed {
|
|
return 0, errClosed
|
|
} else if f.err != nil {
|
|
return 0, f.err
|
|
}
|
|
|
|
n, err = f.file.Write(p)
|
|
if err != nil {
|
|
f.err = err
|
|
}
|
|
|
|
return n, err
|
|
}
|
|
|
|
// Commit causes the current temp file to be safely persisted to disk and atomically renamed to the desired final filename.
|
|
//
|
|
// It is safe to call Close after commit, so you can defer Close as
|
|
// usual without worries about write-safey.
|
|
func (f *File) Commit() error {
|
|
if f.closed {
|
|
return errClosed
|
|
} else if f.err != nil {
|
|
return f.err
|
|
}
|
|
|
|
if err := f.file.Sync(); err != nil {
|
|
return f.cleanup(err)
|
|
}
|
|
|
|
if err := f.file.Chmod(f.perm); err != nil {
|
|
return f.cleanup(err)
|
|
}
|
|
|
|
if err := f.file.Close(); err != nil {
|
|
return f.cleanup(err)
|
|
}
|
|
|
|
if err := Rename(f.tempName, f.name); err != nil {
|
|
return f.cleanup(err)
|
|
}
|
|
|
|
f.closed = true
|
|
|
|
return nil
|
|
}
|
|
|
|
// Close closes the current file and erases it, unless Commit was
|
|
// previously called. In that case it does nothing.
|
|
//
|
|
// Close is idempotent.
|
|
//
|
|
// After Close is called, Write and Commit will fail.
|
|
func (f *File) Close() error {
|
|
if !f.closed {
|
|
_ = f.cleanup(nil)
|
|
f.closed = true
|
|
}
|
|
return f.err
|
|
}
|
|
|
|
func (f *File) cleanup(err error) error {
|
|
_ = f.file.Close()
|
|
_ = os.Remove(f.tempName)
|
|
|
|
if f.err == nil {
|
|
f.err = err
|
|
}
|
|
return f.err
|
|
}
|
|
|
|
// setErr is only used during testing to simulate os.File errors
|
|
func (f *File) setErr(err error) {
|
|
f.err = err
|
|
}
|