io/ioutil: add TempFile

R=r
CC=golang-dev
https://golang.org/cl/1472042

diff --git a/src/pkg/io/ioutil/Makefile b/src/pkg/io/ioutil/Makefile
index 3abf7143a698d5f71076b66830c21f613f88fe14..77b75bcec671203ea4bbae43e0a3a3f2c9518a10 100644 (file)
--- a/src/pkg/io/ioutil/Makefile
+++ b/src/pkg/io/ioutil/Makefile
@@ -7,5 +7,6 @@ include ../../../Make.$(GOARCH)
 TARG=io/ioutil
 GOFILES=\
        ioutil.go\
+       tempfile.go\
 
 include ../../../Make.pkg

diff --git a/src/pkg/io/ioutil/tempfile.go b/src/pkg/io/ioutil/tempfile.go
new file mode 100644 (file)
index 0000000..55fcf47
--- /dev/null
+++ b/src/pkg/io/ioutil/tempfile.go
@@ -0,0 +1,63 @@
+// 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 value of the
+// environment variable $TMPDIR or, if that is empty,/tmp.
+// 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.Getenv("TMPDIR")
+               if dir == "" {
+                       dir = "/tmp"
+               }
+       }
+
+       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
+}

diff --git a/src/pkg/io/ioutil/tempfile_test.go b/src/pkg/io/ioutil/tempfile_test.go
new file mode 100644 (file)
index 0000000..fbe45dc
--- /dev/null
+++ b/src/pkg/io/ioutil/tempfile_test.go
@@ -0,0 +1,29 @@
+// 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_test
+
+import (
+       . "io/ioutil"
+       "os"
+       "testing"
+)
+
+func TestTempFile(t *testing.T) {
+       f, err := TempFile("/_not_exists_", "foo")
+       if f != nil || err == nil {
+               t.Errorf("TempFile(`/_not_exists_`, `foo`) = %v, %v", f, err)
+       }
+
+       f, err = TempFile("/tmp", "ioutil_test")
+       if f == nil || err != nil {
+               t.Errorf("TempFile(`/tmp`, `ioutil_test`) = %v, %v", f, err)
+       }
+       re := testing.MustCompile("^/tmp/ioutil_test[0-9]+$")
+       if !re.MatchString(f.Name()) {
+               t.Fatalf("TempFile(`/tmp`, `ioutil_test`) created bad name %s", f.Name())
+       }
+       os.Remove(f.Name())
+       f.Close()
+}