path/filepath: make UNC file names work

Fixes #2201

R=golang-dev, r, rsc, alex.brainman, robert.hencke, jp
CC=golang-dev
https://golang.org/cl/4950051

src/pkg/path/filepath/path.go

@@ -41,9 +41,12 @@ func Clean(path string) string {
 	vol := VolumeName(path)
 	path = path[len(vol):]
 	if path == "" {
+		if len(vol) > 1 && vol[1] != ':' {
+			// should be UNC
+			return FromSlash(vol)
+		}
 		return vol + "."
 	}
-
 	rooted := os.IsPathSeparator(path[0])
 
 	// Invariants:
@@ -144,8 +147,9 @@ func SplitList(path string) []string {
 // If there is no Separator in path, Split returns an empty dir
 // and file set to path.
 func Split(path string) (dir, file string) {
+	vol := VolumeName(path)
 	i := len(path) - 1
-	for i >= 0 && !os.IsPathSeparator(path[i]) {
+	for i >= len(vol) && !os.IsPathSeparator(path[i]) {
 		i--
 	}
 	return path[:i+1], path[i+1:]

src/pkg/path/filepath/path_test.go

@@ -73,9 +73,17 @@ var wincleantests = []PathTest{
 	{`c:\abc`, `c:\abc`},
 	{`c:abc\..\..\.\.\..\def`, `c:..\..\def`},
 	{`c:\abc\def\..\..`, `c:\`},
+	{`c:\..\abc`, `c:\abc`},
 	{`c:..\abc`, `c:..\abc`},
 	{`\`, `\`},
 	{`/`, `\`},
+	{`\\i\..\c$`, `\c$`},
+	{`\\i\..\i\c$`, `\i\c$`},
+	{`\\i\..\I\c$`, `\I\c$`},
+	{`\\host\share\foo\..\bar`, `\\host\share\bar`},
+	{`//host/share/foo/../baz`, `\\host\share\baz`},
+	{`\\a\b\..\c`, `\\a\b\c`},
+	{`\\a\b`, `\\a\b`},
 }
 
 func TestClean(t *testing.T) {
@@ -146,9 +154,25 @@ var unixsplittests = []SplitTest{
 	{"/", "/", ""},
 }
 
+var winsplittests = []SplitTest{
+	{`c:`, `c:`, ``},
+	{`c:/`, `c:/`, ``},
+	{`c:/foo`, `c:/`, `foo`},
+	{`c:/foo/bar`, `c:/foo/`, `bar`},
+	{`//host/share`, `//host/share`, ``},
+	{`//host/share/`, `//host/share/`, ``},
+	{`//host/share/foo`, `//host/share/`, `foo`},
+	{`\\host\share`, `\\host\share`, ``},
+	{`\\host\share\`, `\\host\share\`, ``},
+	{`\\host\share\foo`, `\\host\share\`, `foo`},
+}
+
 func TestSplit(t *testing.T) {
 	var splittests []SplitTest
 	splittests = unixsplittests
+	if runtime.GOOS == "windows" {
+		splittests = append(splittests, winsplittests...)
+	}
 	for _, test := range splittests {
 		if d, f := filepath.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)
@@ -186,6 +210,8 @@ var winjointests = []JoinTest{
 	{[]string{`C:\Windows\`, ``}, `C:\Windows`},
 	{[]string{`C:\`, `Windows`}, `C:\Windows`},
 	{[]string{`C:`, `Windows`}, `C:\Windows`},
+	{[]string{`\\host\share`, `foo`}, `\\host\share\foo`},
+	{[]string{`//host/share`, `foo/bar`}, `\\host\share\foo\bar`},
 }
 
 // join takes a []string and passes it to Join.
@@ -422,6 +448,8 @@ var winisabstests = []IsAbsTest{
 	{`\`, false},
 	{`\Windows`, false},
 	{`c:a\b`, false},
+	{`\\host\share\foo`, true},
+	{`//host/share/foo/bar`, true},
 }
 
 func TestIsAbs(t *testing.T) {
@@ -574,3 +602,43 @@ func TestAbs(t *testing.T) {
 		}
 	}
 }
+
+type VolumeNameTest struct {
+	path string
+	vol  string
+}
+
+var volumenametests = []VolumeNameTest{
+	{`c:/foo/bar`, `c:`},
+	{`c:`, `c:`},
+	{``, ``},
+	{`\\\host`, ``},
+	{`\\\host\`, ``},
+	{`\\\host\share`, ``},
+	{`\\\host\\share`, ``},
+	{`\\host`, ``},
+	{`//host`, ``},
+	{`\\host\`, ``},
+	{`//host/`, ``},
+	{`\\host\share`, `\\host\share`},
+	{`//host/share`, `//host/share`},
+	{`\\host\share\`, `\\host\share`},
+	{`//host/share/`, `//host/share`},
+	{`\\host\share\foo`, `\\host\share`},
+	{`//host/share/foo`, `//host/share`},
+	{`\\host\share\\foo\\\bar\\\\baz`, `\\host\share`},
+	{`//host/share//foo///bar////baz`, `//host/share`},
+	{`\\host\share\foo\..\bar`, `\\host\share`},
+	{`//host/share/foo/../bar`, `//host/share`},
+}
+
+func TestVolumeName(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+	for _, v := range volumenametests {
+		if vol := filepath.VolumeName(v.path); vol != v.vol {
+			t.Errorf("VolumeName(%q)=%q, want %q", v.path, vol, v.vol)
+		}
+	}
+}

src/pkg/path/filepath/path_windows.go

@@ -4,7 +4,13 @@
 
 package filepath
 
-import "strings"
+import (
+	"strings"
+)
+
+func isSlash(c uint8) bool {
+	return c == '\\' || c == '/'
+}
 
 // IsAbs returns true if the path is absolute.
 func IsAbs(path string) (b bool) {
@@ -16,11 +22,12 @@ func IsAbs(path string) (b bool) {
 	if path == "" {
 		return false
 	}
-	return path[0] == '/' || path[0] == '\\'
+	return isSlash(path[0])
 }
 
 // VolumeName returns leading volume name.  
 // Given "C:\foo\bar" it returns "C:" under windows.
+// Given "\\host\share\foo" it returns "\\host\share".
 // On other platforms it returns "".
 func VolumeName(path string) (v string) {
 	if len(path) < 2 {
@@ -33,6 +40,30 @@ func VolumeName(path string) (v string) {
 			'A' <= c && c <= 'Z') {
 		return path[:2]
 	}
+	// is it UNC
+	if l := len(path); l >= 5 && isSlash(path[0]) && isSlash(path[1]) &&
+		!isSlash(path[2]) && path[2] != '.' {
+		// first, leading `\\` and next shouldn't be `\`. its server name.
+		for n := 3; n < l-1; n++ {
+			// second, next '\' shouldn't be repeated.
+			if isSlash(path[n]) {
+				n++
+				// third, following something characters. its share name.
+				if !isSlash(path[n]) {
+					if path[n] == '.' {
+						break
+					}
+					for ; n < l; n++ {
+						if isSlash(path[n]) {
+							break
+						}
+					}
+					return path[:n]
+				}
+				break
+			}
+		}
+	}
 	return ""
 }