syscall: implement chmod() for win32.

R=golang-dev, rsc, brainman
CC=golang-dev
https://golang.org/cl/4175049

src/pkg/syscall/syscall_windows.go

@@ -154,6 +154,7 @@ func NewCallback(fn interface{}) uintptr
 //sys	SetEnvironmentVariable(name *uint16, value *uint16) (errno int) = kernel32.SetEnvironmentVariableW
 //sys	SetFileTime(handle int32, ctime *Filetime, atime *Filetime, wtime *Filetime) (errno int)
 //sys	GetFileAttributes(name *uint16) (attrs uint32, errno int) [failretval==INVALID_FILE_ATTRIBUTES] = kernel32.GetFileAttributesW
+//sys	SetFileAttributes(name *uint16, attrs uint32) (errno int) [failretval==INVALID_FILE_ATTRIBUTES] = kernel32.SetFileAttributesW
 //sys	GetCommandLine() (cmd *uint16) = kernel32.GetCommandLineW
 //sys	CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, errno int) [failretval==nil] = shell32.CommandLineToArgvW
 //sys	LocalFree(hmem uint32) (handle uint32, errno int) [failretval!=0]
@@ -718,11 +719,31 @@ func Fchdir(fd int) (errno int)                           { return EWINDOWS }
 func Link(oldpath, newpath string) (errno int)            { return EWINDOWS }
 func Symlink(path, link string) (errno int)               { return EWINDOWS }
 func Readlink(path string, buf []byte) (n int, errno int) { return 0, EWINDOWS }
-func Chmod(path string, mode uint32) (errno int)          { return EWINDOWS }
-func Fchmod(fd int, mode uint32) (errno int)              { return EWINDOWS }
-func Chown(path string, uid int, gid int) (errno int)     { return EWINDOWS }
-func Lchown(path string, uid int, gid int) (errno int)    { return EWINDOWS }
-func Fchown(fd int, uid int, gid int) (errno int)         { return EWINDOWS }
+
+func Chmod(path string, mode uint32) (errno int) {
+	attrs, errno := GetFileAttributes(StringToUTF16Ptr(path))
+	if errno != 0 {
+		return
+	}
+
+	if mode == 0 {
+		return EINVAL
+	}
+
+	if mode&S_IWRITE != 0 {
+		attrs &^= FILE_ATTRIBUTE_READONLY
+	} else if attrs&FILE_ATTRIBUTE_READONLY == 0 {
+		attrs |= FILE_ATTRIBUTE_READONLY
+	}
+
+	errno = SetFileAttributes(StringToUTF16Ptr(path), attrs)
+	return
+}
+
+func Fchmod(fd int, mode uint32) (errno int)           { return EWINDOWS }
+func Chown(path string, uid int, gid int) (errno int)  { return EWINDOWS }
+func Lchown(path string, uid int, gid int) (errno int) { return EWINDOWS }
+func Fchown(fd int, uid int, gid int) (errno int)      { return EWINDOWS }
 
 func Getuid() (uid int)                  { return -1 }
 func Geteuid() (euid int)                { return -1 }

src/pkg/syscall/zsyscall_windows_386.go

@@ -63,6 +63,7 @@ var (
 	procSetEnvironmentVariableW    = getSysProcAddr(modkernel32, "SetEnvironmentVariableW")
 	procSetFileTime                = getSysProcAddr(modkernel32, "SetFileTime")
 	procGetFileAttributesW         = getSysProcAddr(modkernel32, "GetFileAttributesW")
+	procSetFileAttributesW         = getSysProcAddr(modkernel32, "SetFileAttributesW")
 	procGetCommandLineW            = getSysProcAddr(modkernel32, "GetCommandLineW")
 	procCommandLineToArgvW         = getSysProcAddr(modshell32, "CommandLineToArgvW")
 	procLocalFree                  = getSysProcAddr(modkernel32, "LocalFree")
@@ -806,6 +807,20 @@ func GetFileAttributes(name *uint16) (attrs uint32, errno int) {
 	return
 }
 
+func SetFileAttributes(name *uint16, attrs uint32) (errno int) {
+	r0, _, e1 := Syscall(procSetFileAttributesW, 2, uintptr(unsafe.Pointer(name)), uintptr(attrs), 0)
+	if int(r0) == 0 {
+		if e1 != 0 {
+			errno = int(e1)
+		} else {
+			errno = EINVAL
+		}
+	} else {
+		errno = 0
+	}
+	return
+}
+
 func GetCommandLine() (cmd *uint16) {
 	r0, _, _ := Syscall(procGetCommandLineW, 0, 0, 0, 0)
 	cmd = (*uint16)(unsafe.Pointer(r0))

src/pkg/syscall/ztypes_windows_386.go

@@ -380,6 +380,7 @@ const (
 	S_ISGID    = 0x400
 	S_ISVTX    = 0x200
 	S_IRUSR    = 0x100
+	S_IWRITE   = 0x80
 	S_IWUSR    = 0x80
 	S_IXUSR    = 0x40
 )