io/ioutil: forward TempFile and TempDir to os package

For #42026
Fixes #44311

Change-Id: I3dabcf902d155f95800b4adf1d7578906a194ce6
Reviewed-on: https://go-review.googlesource.com/c/go/+/285378
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>

3 files changed, 13 insertions, 115 deletions

diff --git a/src/io/ioutil/export_test.go b/src/io/ioutil/export_test.go
deleted file mode 100644
index dff55f07e2..0000000000
--- a/src/io/ioutil/export_test.go
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2020 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
-
-var ErrPatternHasSeparator = errPatternHasSeparator
diff --git a/src/io/ioutil/tempfile.go b/src/io/ioutil/tempfile.go
index af7c6fd7c1..4b272e5a5d 100644
--- a/src/io/ioutil/tempfile.go
+++ b/src/io/ioutil/tempfile.go
@@ -5,38 +5,9 @@
 package ioutil
 
 import (
-	"errors"
 	"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
@@ -48,48 +19,10 @@ func nextRandom() string {
 // 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.
+//
+// As of Go 1.16, this function simply calls os.CreateTemp.
 func TempFile(dir, pattern string) (f *os.File, err error) {
-	if dir == "" {
-		dir = os.TempDir()
-	}
-
-	prefix, suffix, err := prefixAndSuffix(pattern)
-	if err != nil {
-		return
-	}
-
-	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
-}
-
-var errPatternHasSeparator = errors.New("pattern contains path separator")
-
-// 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, err error) {
-	if strings.ContainsRune(pattern, os.PathSeparator) {
-		err = errPatternHasSeparator
-		return
-	}
-	if pos := strings.LastIndex(pattern, "*"); pos != -1 {
-		prefix, suffix = pattern[:pos], pattern[pos+1:]
-	} else {
-		prefix = pattern
-	}
-	return
+	return os.CreateTemp(dir, pattern)
 }
 
 // TempDir creates a new temporary directory in the directory dir.
@@ -101,37 +34,8 @@ func prefixAndSuffix(pattern string) (prefix, suffix string, err error) {
 // 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.
+//
+// As of Go 1.16, this function simply calls os.MkdirTemp.
 func TempDir(dir, pattern string) (name string, err error) {
-	if dir == "" {
-		dir = os.TempDir()
-	}
-
-	prefix, suffix, err := prefixAndSuffix(pattern)
-	if err != nil {
-		return
-	}
-
-	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
+	return os.MkdirTemp(dir, pattern)
 }
diff --git a/src/io/ioutil/tempfile_test.go b/src/io/ioutil/tempfile_test.go
index 440c7cffc6..5cef18c33b 100644
--- a/src/io/ioutil/tempfile_test.go
+++ b/src/io/ioutil/tempfile_test.go
@@ -50,6 +50,9 @@ func TestTempFile_pattern(t *testing.T) {
 	}
 }
 
+// This string is from os.errPatternHasSeparator.
+const patternHasSeparator = "pattern contains path separator"
+
 func TestTempFile_BadPattern(t *testing.T) {
 	tmpDir, err := TempDir("", t.Name())
 	if err != nil {
@@ -81,9 +84,8 @@ func TestTempFile_BadPattern(t *testing.T) {
 			if tt.wantErr {
 				if err == nil {
 					t.Errorf("Expected an error for pattern %q", tt.pattern)
-				}
-				if g, w := err, ErrPatternHasSeparator; g != w {
-					t.Errorf("Error mismatch: got %#v, want %#v for pattern %q", g, w, tt.pattern)
+				} else if !strings.Contains(err.Error(), patternHasSeparator) {
+					t.Errorf("Error mismatch: got %#v, want %q for pattern %q", err, patternHasSeparator, tt.pattern)
 				}
 			} else if err != nil {
 				t.Errorf("Unexpected error %v for pattern %q", err, tt.pattern)
@@ -183,9 +185,8 @@ func TestTempDir_BadPattern(t *testing.T) {
 			if tt.wantErr {
 				if err == nil {
 					t.Errorf("Expected an error for pattern %q", tt.pattern)
-				}
-				if g, w := err, ErrPatternHasSeparator; g != w {
-					t.Errorf("Error mismatch: got %#v, want %#v for pattern %q", g, w, tt.pattern)
+				} else if !strings.Contains(err.Error(), patternHasSeparator) {
+					t.Errorf("Error mismatch: got %#v, want %q for pattern %q", err, patternHasSeparator, tt.pattern)
 				}
 			} else if err != nil {
 				t.Errorf("Unexpected error %v for pattern %q", err, tt.pattern)