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io/ioutil: add TempFile
R=r CC=golang-dev https://golang.org/cl/1472042
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parent
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@ -7,5 +7,6 @@ include ../../../Make.$(GOARCH)
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TARG=io/ioutil
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GOFILES=\
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ioutil.go\
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tempfile.go\
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include ../../../Make.pkg
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63
src/pkg/io/ioutil/tempfile.go
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63
src/pkg/io/ioutil/tempfile.go
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@ -0,0 +1,63 @@
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// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ioutil
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import (
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"os"
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"strconv"
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)
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// Random number state, accessed without lock; racy but harmless.
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// We generate random temporary file names so that there's a good
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// chance the file doesn't exist yet - keeps the number of tries in
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// TempFile to a minimum.
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var rand uint32
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func reseed() uint32 {
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sec, nsec, _ := os.Time()
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return uint32(sec*1e9 + nsec + int64(os.Getpid()))
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}
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func nextSuffix() string {
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r := rand
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if r == 0 {
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r = reseed()
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}
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r = r*1664525 + 1013904223 // constants from Numerical Recipes
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rand = r
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return strconv.Itoa(int(1e9 + r%1e9))[1:]
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}
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// TempFile creates a new temporary file in the directory dir
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// with a name beginning with prefix, opens the file for reading
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// and writing, and returns the resulting *os.File.
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// If dir is the empty string, TempFile uses the value of the
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// environment variable $TMPDIR or, if that is empty,/tmp.
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// Multiple programs calling TempFile simultaneously
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// will not choose the same file. The caller can use f.Name()
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// to find the name of the file. It is the caller's responsibility to
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// remove the file when no longer needed.
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func TempFile(dir, prefix string) (f *os.File, err os.Error) {
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if dir == "" {
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dir = os.Getenv("TMPDIR")
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if dir == "" {
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dir = "/tmp"
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}
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}
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nconflict := 0
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for i := 0; i < 10000; i++ {
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name := dir + "/" + prefix + nextSuffix()
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f, err = os.Open(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
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if pe, ok := err.(*os.PathError); ok && pe.Error == os.EEXIST {
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if nconflict++; nconflict > 10 {
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rand = reseed()
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}
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continue
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}
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break
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}
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return
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}
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29
src/pkg/io/ioutil/tempfile_test.go
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29
src/pkg/io/ioutil/tempfile_test.go
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@ -0,0 +1,29 @@
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// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ioutil_test
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import (
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. "io/ioutil"
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"os"
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"testing"
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)
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func TestTempFile(t *testing.T) {
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f, err := TempFile("/_not_exists_", "foo")
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if f != nil || err == nil {
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t.Errorf("TempFile(`/_not_exists_`, `foo`) = %v, %v", f, err)
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}
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f, err = TempFile("/tmp", "ioutil_test")
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if f == nil || err != nil {
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t.Errorf("TempFile(`/tmp`, `ioutil_test`) = %v, %v", f, err)
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}
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re := testing.MustCompile("^/tmp/ioutil_test[0-9]+$")
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if !re.MatchString(f.Name()) {
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t.Fatalf("TempFile(`/tmp`, `ioutil_test`) created bad name %s", f.Name())
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}
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os.Remove(f.Name())
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f.Close()
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}
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