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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"
"strconv"
)
// Random number state, accessed without lock; racy but harmless.
// 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
func reseed() uint32 {
sec, nsec, _ := os.Time()
return uint32(sec*1e9 + nsec + int64(os.Getpid()))
}
func nextSuffix() string {
r := rand
if r == 0 {
r = reseed()
}
r = r*1664525 + 1013904223 // constants from Numerical Recipes
rand = r
return strconv.Itoa(int(1e9 + r%1e9))[1:]
}
// TempFile creates a new temporary file in the directory dir
// with a name beginning with prefix, opens the file for reading
// and writing, and returns the resulting *os.File.
// 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 name of the file. It is the caller's responsibility to
// remove the file when no longer needed.
func TempFile(dir, prefix string) (f *os.File, err os.Error) {
if dir == "" {
dir = os.TempDir()
}
nconflict := 0
for i := 0; i < 10000; i++ {
name := dir + "/" + prefix + nextSuffix()
f, err = os.Open(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
if pe, ok := err.(*os.PathError); ok && pe.Error == os.EEXIST {
if nconflict++; nconflict > 10 {
rand = reseed()
}
continue
}
break
}
return
}
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