os, syscall: windows really isn't posix compliant, fix os.IsExist()

R=golang-dev, rsc, bradfitz, alex.brainman
CC=golang-dev
https://golang.org/cl/5754083

src/pkg/os/error_posix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd windows
+// +build darwin freebsd linux netbsd openbsd
 
 package os
 

src/pkg/os/error_test.go

@@ -0,0 +1,31 @@
+// Copyright 2012 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 os_test
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestErrIsExist(t *testing.T) {
+	f, err := ioutil.TempFile("", "_Go_ErrIsExist")
+	if err != nil {
+		t.Fatalf("open ErrIsExist tempfile: %s", err)
+		return
+	}
+	defer os.Remove(f.Name())
+	defer f.Close()
+	f2, err := os.OpenFile(f.Name(), os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
+	if err == nil {
+		f2.Close()
+		t.Fatal("Open should have failed")
+		return
+	}
+	if !os.IsExist(err) {
+		t.Fatalf("os.IsExist does not work as expected for %#v", err)
+		return
+	}
+}

src/pkg/os/error_windows.go

@@ -0,0 +1,35 @@
+// Copyright 2012 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 os
+
+import "syscall"
+
+// IsExist returns whether the error is known to report that a file already exists.
+// It is satisfied by ErrExist as well as some syscall errors.
+func IsExist(err error) bool {
+	if pe, ok := err.(*PathError); ok {
+		err = pe.Err
+	}
+	return err == syscall.EEXIST || err == syscall.ERROR_ALREADY_EXISTS ||
+		err == syscall.ERROR_FILE_EXISTS || err == ErrExist
+}
+
+// IsNotExist returns whether the error is known to report that a file does not exist.
+// It is satisfied by ErrNotExist as well as some syscall errors.
+func IsNotExist(err error) bool {
+	if pe, ok := err.(*PathError); ok {
+		err = pe.Err
+	}
+	return err == syscall.ENOENT || err == ErrNotExist
+}
+
+// IsPermission returns whether the error is known to report that permission is denied.
+// It is satisfied by ErrPermission as well as some syscall errors.
+func IsPermission(err error) bool {
+	if pe, ok := err.(*PathError); ok {
+		err = pe.Err
+	}
+	return err == syscall.EACCES || err == syscall.EPERM || err == ErrPermission
+}

src/pkg/syscall/ztypes_windows.go

@@ -10,11 +10,13 @@ const (
 	ERROR_PATH_NOT_FOUND      Errno = 3
 	ERROR_ACCESS_DENIED       Errno = 5
 	ERROR_NO_MORE_FILES       Errno = 18
+	ERROR_FILE_EXISTS         Errno = 80
 	ERROR_BROKEN_PIPE         Errno = 109
 	ERROR_BUFFER_OVERFLOW     Errno = 111
 	ERROR_INSUFFICIENT_BUFFER Errno = 122
 	ERROR_MOD_NOT_FOUND       Errno = 126
 	ERROR_PROC_NOT_FOUND      Errno = 127
+	ERROR_ALREADY_EXISTS      Errno = 183
 	ERROR_ENVVAR_NOT_FOUND    Errno = 203
 	ERROR_OPERATION_ABORTED   Errno = 995
 	ERROR_IO_PENDING          Errno = 997