archive/zip: support full range of FileMode flags

Zip files may actually store symlinks, and that's represented
as a file with unix flag S_IFLNK and with its data containing
the symlink target name.

The other flags are being supported too. Now that the os package
has the full range of flags in a system agnostic manner, there's
no reason to discard that information.

R=golang-dev, adg, rogpeppe
CC=golang-dev
https://golang.org/cl/5624048

src/pkg/archive/zip/reader_test.go

@@ -69,8 +69,23 @@ var tests = []ZipTest{
 			},
 		},
 	},
-	{Name: "readme.zip"},
+	{
-	{Name: "readme.notzip", Error: ErrFormat},
+		Name: "symlink.zip",
+		File: []ZipTestFile{
+			{
+				Name:    "symlink",
+				Content: []byte("../target"),
+				Mode:    0777 | os.ModeSymlink,
+			},
+		},
+	},
+	{
+		Name: "readme.zip",
+	},
+	{
+		Name:  "readme.notzip",
+		Error: ErrFormat,
+	},
 	{
 		Name: "dd.zip",
 		File: []ZipTestFile{

src/pkg/archive/zip/struct.go

@@ -152,13 +152,20 @@ func (h *FileHeader) SetModTime(t time.Time) {
 	h.ModifiedDate, h.ModifiedTime = timeToMsDosTime(t)
 }
 
-// traditional names for Unix constants
 const (
+	// Unix constants. The specification doesn't mention them,
+	// but these seem to be the values agreed on by tools.
 	s_IFMT   = 0xf000
-	s_IFDIR = 0x4000
+	s_IFSOCK = 0xc000
+	s_IFLNK  = 0xa000
 	s_IFREG  = 0x8000
+	s_IFBLK  = 0x6000
+	s_IFDIR  = 0x4000
+	s_IFCHR  = 0x2000
+	s_IFIFO  = 0x1000
 	s_ISUID  = 0x800
 	s_ISGID  = 0x400
+	s_ISVTX  = 0x200
 
 	msdosDir      = 0x10
 	msdosReadOnly = 0x01
@@ -206,10 +213,23 @@ func msdosModeToFileMode(m uint32) (mode os.FileMode) {
 
 func fileModeToUnixMode(mode os.FileMode) uint32 {
 	var m uint32
-	if mode&os.ModeDir != 0 {
+	switch mode & os.ModeType {
-		m = s_IFDIR
+	default:
-	} else {
 		m = s_IFREG
+	case os.ModeDir:
+		m = s_IFDIR
+	case os.ModeSymlink:
+		m = s_IFLNK
+	case os.ModeNamedPipe:
+		m = s_IFIFO
+	case os.ModeSocket:
+		m = s_IFSOCK
+	case os.ModeDevice:
+		if mode&os.ModeCharDevice != 0 {
+			m = s_IFCHR
+		} else {
+			m = s_IFBLK
+		}
 	}
 	if mode&os.ModeSetuid != 0 {
 		m |= s_ISUID
@@ -217,13 +237,29 @@ func fileModeToUnixMode(mode os.FileMode) uint32 {
 	if mode&os.ModeSetgid != 0 {
 		m |= s_ISGID
 	}
+	if mode&os.ModeSticky != 0 {
+		m |= s_ISVTX
+	}
 	return m | uint32(mode&0777)
 }
 
 func unixModeToFileMode(m uint32) os.FileMode {
-	var mode os.FileMode
+	mode := os.FileMode(m & 0777)
-	if m&s_IFMT == s_IFDIR {
+	switch m & s_IFMT {
+	case s_IFBLK:
+		mode |= os.ModeDevice
+	case s_IFCHR:
+		mode |= os.ModeDevice | os.ModeCharDevice
+	case s_IFDIR:
 		mode |= os.ModeDir
+	case s_IFIFO:
+		mode |= os.ModeNamedPipe
+	case s_IFLNK:
+		mode |= os.ModeSymlink
+	case s_IFREG:
+		// nothing to do
+	case s_IFSOCK:
+		mode |= os.ModeSocket
 	}
 	if m&s_ISGID != 0 {
 		mode |= os.ModeSetgid
@@ -231,5 +267,8 @@ func unixModeToFileMode(m uint32) os.FileMode {
 	if m&s_ISUID != 0 {
 		mode |= os.ModeSetuid
 	}
-	return mode | os.FileMode(m&0777)
+	if m&s_ISVTX != 0 {
+		mode |= os.ModeSticky
+	}
+	return mode
 }

src/pkg/archive/zip/writer_test.go

@@ -47,10 +47,10 @@ var writeTests = []WriteTest{
 		Mode:   0755 | os.ModeSetgid,
 	},
 	{
-		Name:   "setgid",
+		Name:   "symlink",
-		Data:   []byte("setgid file"),
+		Data:   []byte("../link/target"),
 		Method: Deflate,
-		Mode:   0755 | os.ModeSetgid,
+		Mode:   0755 | os.ModeSymlink,
 	},
 }