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// Copyright 2010 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.
package ioutil
import (
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
)
// Random number state.
// We generate random temporary file names so that there's a good
// chance the file doesn't exist yet - keeps the number of tries in
// TempFile to a minimum.
var rand uint32
var randmu sync.Mutex
func reseed() uint32 {
return uint32(time.Now().UnixNano() + int64(os.Getpid()))
}
func nextRandom() string {
randmu.Lock()
r := rand
if r == 0 {
r = reseed()
}
r = r*1664525 + 1013904223 // constants from Numerical Recipes
rand = r
randmu.Unlock()
return strconv.Itoa(int(1e9 + r%1e9))[1:]
}
// TempFile creates a new temporary file in the directory dir,
// opens the file for reading and writing, and returns the resulting *os.File.
// The filename is generated by taking pattern and adding a random
// string to the end. If pattern includes a "*", the random string
// replaces the last "*".
// If dir is the empty string, TempFile uses the default directory
// for temporary files (see os.TempDir).
// Multiple programs calling TempFile simultaneously
// will not choose the same file. The caller can use f.Name()
// to find the pathname of the file. It is the caller's responsibility
// to remove the file when no longer needed.
func TempFile(dir, pattern string) (f *os.File, err error) {
if dir == "" {
dir = os.TempDir()
}
prefix, suffix := prefixAndSuffix(pattern)
nconflict := 0
for i := 0; i < 10000; i++ {
name := filepath.Join(dir, prefix+nextRandom()+suffix)
f, err = os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
if os.IsExist(err) {
if nconflict++; nconflict > 10 {
randmu.Lock()
rand = reseed()
randmu.Unlock()
}
continue
}
break
}
return
}
// prefixAndSuffix splits pattern by the last wildcard "*", if applicable,
// returning prefix as the part before "*" and suffix as the part after "*".
func prefixAndSuffix(pattern string) (prefix, suffix string) {
if pos := strings.LastIndex(pattern, "*"); pos != -1 {
prefix, suffix = pattern[:pos], pattern[pos+1:]
} else {
prefix = pattern
}
return
}
// TempDir creates a new temporary directory in the directory dir.
// The directory name is generated by taking pattern and applying a
// random string to the end. If pattern includes a "*", the random string
// replaces the last "*". TempDir returns the name of the new directory.
// If dir is the empty string, TempDir uses the
// default directory for temporary files (see os.TempDir).
// Multiple programs calling TempDir simultaneously
// will not choose the same directory. It is the caller's responsibility
// to remove the directory when no longer needed.
func TempDir(dir, pattern string) (name string, err error) {
if dir == "" {
dir = os.TempDir()
}
prefix, suffix := prefixAndSuffix(pattern)
nconflict := 0
for i := 0; i < 10000; i++ {
try := filepath.Join(dir, prefix+nextRandom()+suffix)
err = os.Mkdir(try, 0700)
if os.IsExist(err) {
if nconflict++; nconflict > 10 {
randmu.Lock()
rand = reseed()
randmu.Unlock()
}
continue
}
if os.IsNotExist(err) {
if _, err := os.Stat(dir); os.IsNotExist(err) {
return "", err
}
}
if err == nil {
name = try
}
break
}
return
}
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