forked from perkeep/perkeep
/
simplefilefiler.go
123 lines (100 loc) · 3 KB
/
simplefilefiler.go
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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// A basic os.File backed Filer.
package lldb
import (
"os"
"camlistore.org/third_party/github.com/cznic/fileutil"
"camlistore.org/third_party/github.com/cznic/mathutil"
)
var _ Filer = &SimpleFileFiler{} // Ensure SimpleFileFiler is a Filer.
// SimpleFileFiler is an os.File backed Filer intended for use where structural
// consistency can be reached by other means (SimpleFileFiler is for example
// wrapped in eg. an RollbackFiler or ACIDFiler0) or where persistence is not
// required (temporary/working data sets).
//
// SimpleFileFiler is the most simple os.File backed Filer implementation as it
// does not really implement BeginUpdate and EndUpdate/Rollback in any way
// which would protect the structural integrity of data. If misused e.g. as a
// real database storage w/o other measures, it can easily cause data loss
// when, for example, a power outage occurs or the updating process terminates
// abruptly.
type SimpleFileFiler struct {
file *os.File
nest int
size int64 // not set if < 0
}
// NewSimpleFileFiler returns a new SimpleFileFiler.
func NewSimpleFileFiler(f *os.File) *SimpleFileFiler {
return &SimpleFileFiler{file: f, size: -1}
}
// BeginUpdate implements Filer.
func (f *SimpleFileFiler) BeginUpdate() error {
f.nest++
return nil
}
// Close implements Filer.
func (f *SimpleFileFiler) Close() (err error) {
if f.nest != 0 {
return &ErrPERM{(f.Name() + ":Close")}
}
return f.file.Close()
}
// EndUpdate implements Filer.
func (f *SimpleFileFiler) EndUpdate() (err error) {
if f.nest == 0 {
return &ErrPERM{(f.Name() + ":EndUpdate")}
}
f.nest--
return
}
// Name implements Filer.
func (f *SimpleFileFiler) Name() string {
return f.file.Name()
}
// PunchHole implements Filer.
func (f *SimpleFileFiler) PunchHole(off, size int64) (err error) {
return fileutil.PunchHole(f.file, off, size)
}
// ReadAt implements Filer.
func (f *SimpleFileFiler) ReadAt(b []byte, off int64) (n int, err error) {
return f.file.ReadAt(b, off)
}
// Rollback implements Filer.
func (f *SimpleFileFiler) Rollback() (err error) { return }
// Size implements Filer.
func (f *SimpleFileFiler) Size() (int64, error) {
if f.size < 0 { // boot
fi, err := os.Stat(f.file.Name())
if err != nil {
return 0, err
}
f.size = fi.Size()
}
return f.size, nil
}
// Sync implements Filer.
func (f *SimpleFileFiler) Sync() error {
return f.file.Sync()
}
// Truncate implements Filer.
func (f *SimpleFileFiler) Truncate(size int64) (err error) {
if size < 0 {
return &ErrINVAL{"Truncate size", size}
}
f.size = size
return f.file.Truncate(size)
}
// WriteAt implements Filer.
func (f *SimpleFileFiler) WriteAt(b []byte, off int64) (n int, err error) {
if f.size < 0 { // boot
fi, err := os.Stat(f.file.Name())
if err != nil {
return 0, err
}
f.size = fi.Size()
}
f.size = mathutil.MaxInt64(f.size, int64(len(b))+off)
return f.file.WriteAt(b, off)
}