/
writer.go
129 lines (108 loc) · 2.83 KB
/
writer.go
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// Copyright 2020 xgfone, 2023 idk
//
// 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.
package metainfo
import (
"io"
"os"
"path/filepath"
)
// Writer is used to write the data referred by the torrent file.
type Writer interface {
io.Closer
io.WriterAt
Info() Info
WriteBlock(pieceIndex, pieceOffset uint32, p []byte) (int, error)
}
const wflag = os.O_WRONLY | os.O_CREATE
type writer struct {
info Info
root string
mode os.FileMode
files map[string]*os.File
}
// NewWriter returns a new Writer.
//
// If fileMode is equal to 0, it is 0600 by default.
//
// Notice: fileMode is only used when writing the data.
func NewWriter(rootDir string, info Info, fileMode os.FileMode) Writer {
if fileMode == 0 {
fileMode = 0600
}
return &writer{
root: rootDir,
info: info,
mode: fileMode,
files: make(map[string]*os.File, len(info.Files)),
}
}
func (w *writer) open(filename string) (f *os.File, err error) {
if w.files == nil {
w.files = make(map[string]*os.File, len(w.info.Files))
}
f, ok := w.files[filename]
if !ok {
if err = os.MkdirAll(filepath.Dir(filename), 0700); err == nil {
if f, err = os.OpenFile(filename, wflag, w.mode); err == nil {
w.files[filename] = f
}
}
}
return
}
func (w *writer) Info() Info { return w.info }
// Close implements the interface io.Closer to closes the opened files.
func (w *writer) Close() error {
for name, file := range w.files {
if file != nil {
file.Close()
delete(w.files, name)
}
}
return nil
}
// WriteBlock writes a data block.
func (w *writer) WriteBlock(pieceIndex, pieceOffset uint32, p []byte) (int, error) {
return w.WriteAt(p, w.info.PieceOffset(pieceIndex, pieceOffset))
}
// WriteAt implements the interface io.WriterAt.
func (w *writer) WriteAt(p []byte, offset int64) (n int, err error) {
var m int
var f *os.File
for _len := len(p); n < _len; {
file, fileOffset := w.info.GetFileByOffset(offset)
if file.Length == 0 || file.Length == fileOffset {
err = io.ErrShortWrite
break
}
length := int(file.Length-fileOffset) + n
if _len < length {
length = _len
} else if length <= n {
break
}
filename := file.PathWithPrefix(w.root, w.info)
if f, err = w.open(filename); err != nil {
break
}
m, err = f.WriteAt(p[n:length], fileOffset)
n += m
offset += int64(m)
if err != nil {
break
}
f.Sync()
}
return
}