path: Windows support for Split

Make Split work on backslashes as well as on slashes under Windows
and support the "C:filename" special case. Also add corresponding
tests.

R=r, rsc, PeterGo, r2, brainman
CC=golang-dev
https://golang.org/cl/3008041

src/pkg/path/Makefile

@@ -9,4 +9,21 @@ GOFILES=\
 	match.go\
 	path.go\
 
+GOFILES_freebsd=\
+	path_unix.go
+
+GOFILES_darwin=\
+	path_unix.go
+
+GOFILES_linux=\
+	path_unix.go
+
+GOFILES_nacl=\
+	path_unix.go
+
+GOFILES_windows=\
+	path_windows.go
+
+GOFILES+=$(GOFILES_$(GOOS))
+
 include ../../Make.pkg

src/pkg/path/path.go

@@ -102,17 +102,13 @@ func Clean(path string) string {
 	return string(buf[0:w])
 }
 
-// Split splits path immediately following the final slash,
+// Split splits path immediately following the final path separator,
 // separating it into a directory and file name component.
-// If there is no slash in path, Split returns an empty dir and
+// If there is no separator in path, Split returns an empty dir and
 // file set to path.
 func Split(path string) (dir, file string) {
-	for i := len(path) - 1; i >= 0; i-- {
-		if path[i] == '/' {
-			return path[0 : i+1], path[i+1:]
-		}
-	}
-	return "", path
+	i := strings.LastIndexAny(path, PathSeps)
+	return path[:i+1], path[i+1:]
 }
 
 // Join joins any number of path elements into a single path, adding a

src/pkg/path/path_test.go

@@ -6,6 +6,7 @@ package path
 
 import (
 	"os"
+	"runtime"
 	"testing"
 )
 
@@ -83,7 +84,18 @@ var splittests = []SplitTest{
 	{"/", "/", ""},
 }
 
+var winsplittests = []SplitTest{
+	{`C:\Windows\System32`, `C:\Windows\`, `System32`},
+	{`C:\Windows\`, `C:\Windows\`, ``},
+	{`C:\Windows`, `C:\`, `Windows`},
+	{`C:Windows`, `C:`, `Windows`},
+	{`\\?\c:\`, `\\?\c:\`, ``},
+}
+
 func TestSplit(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		splittests = append(splittests, winsplittests...)
+	}
 	for _, test := range splittests {
 		if d, f := Split(test.path); d != test.dir || f != test.file {
 			t.Errorf("Split(%q) = %q, %q, want %q, %q", test.path, d, f, test.dir, test.file)

src/pkg/path/path_unix.go

@@ -0,0 +1,11 @@
+// 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 path
+
+const (
+	DirSeps    = `/`                  // directory separators
+	VolumeSeps = ``                   // volume separators
+	PathSeps   = DirSeps + VolumeSeps // all path separators
+)

src/pkg/path/path_windows.go

@@ -0,0 +1,11 @@
+// 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 path
+
+const (
+	DirSeps    = `\/`                 // directory separators
+	VolumeSeps = `:`                  // volume separators
+	PathSeps   = DirSeps + VolumeSeps // all path separators
+)