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// Copyright 2009 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.
// Utility functions.
package ioutil
import (
"bytes"
"io"
"os"
"sort"
)
// ReadAll reads from r until an error or EOF and returns the data it read.
func ReadAll(r io.Reader) ([]byte, os.Error) {
var buf bytes.Buffer
_, err := io.Copy(&buf, r)
return buf.Bytes(), err
}
// ReadFile reads the file named by filename and returns the contents.
func ReadFile(filename string) ([]byte, os.Error) {
f, err := os.Open(filename, os.O_RDONLY, 0)
if err != nil {
return nil, err
}
defer f.Close()
// It's a good but not certain bet that FileInfo will tell us exactly how much to
// read, so let's try it but be prepared for the answer to be wrong.
fi, err := f.Stat()
var n int64
if err == nil && fi.Size < 2e9 { // Don't preallocate a huge buffer, just in case.
n = fi.Size
}
// Add a little extra in case Size is zero, and to avoid another allocation after
// Read has filled the buffer.
n += bytes.MinRead
// Pre-allocate the correct size of buffer, then set its size to zero. The
// Buffer will read into the allocated space cheaply. If the size was wrong,
// we'll either waste some space off the end or reallocate as needed, but
// in the overwhelmingly common case we'll get it just right.
buf := bytes.NewBuffer(make([]byte, 0, n))
_, err = buf.ReadFrom(f)
return buf.Bytes(), err
}
// WriteFile writes data to a file named by filename.
// If the file does not exist, WriteFile creates it with permissions perm;
// otherwise WriteFile truncates it before writing.
func WriteFile(filename string, data []byte, perm uint32) os.Error {
f, err := os.Open(filename, os.O_WRONLY|os.O_CREAT|os.O_TRUNC, perm)
if err != nil {
return err
}
n, err := f.Write(data)
f.Close()
if err == nil && n < len(data) {
err = io.ErrShortWrite
}
return err
}
// A dirList implements sort.Interface.
type fileInfoList []*os.FileInfo
func (f fileInfoList) Len() int { return len(f) }
func (f fileInfoList) Less(i, j int) bool { return f[i].Name < f[j].Name }
func (f fileInfoList) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
// ReadDir reads the directory named by dirname and returns
// a list of sorted directory entries.
func ReadDir(dirname string) ([]*os.FileInfo, os.Error) {
f, err := os.Open(dirname, os.O_RDONLY, 0)
if err != nil {
return nil, err
}
list, err := f.Readdir(-1)
f.Close()
if err != nil {
return nil, err
}
fi := make(fileInfoList, len(list))
for i := range list {
fi[i] = &list[i]
}
sort.Sort(fi)
return fi, nil
}
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