Add os.Link, os.Symlink, os.Readlink.

R=r,rsc
DELTA=161  (161 added, 0 deleted, 0 changed)
OCL=28745
CL=28747

src/lib/os/file.go

@@ -306,3 +306,30 @@ func Remove(name string) Error {
 	return ErrnoToError(e);
 }
 
+// Link creates a hard link.
+func Link(oldpath, newpath string) Error {
+	r, e := syscall.Link(oldpath, newpath);
+	return ErrnoToError(e);
+}
+
+// Symlink creates a symbolic link.
+func Symlink(oldpath, newpath string) Error {
+	r, e := syscall.Symlink(oldpath, newpath);
+	return ErrnoToError(e);
+}
+
+// Readlink reads the contents of a symbolic link: the destination of
+// the link.  It returns the contents and an Error, if any.
+func Readlink(path string) (string, Error) {
+	for len := int64(128); ; len *= 2 {
+		b := make([]byte, len);
+		r, e := syscall.Readlink(path, &b[0], len);
+		if r == -1 {
+			return "", ErrnoToError(e);
+		} else if r < len {
+			return string(b[0:r]), nil;
+		}
+	}
+	// Silence 6g.
+	return "", nil;
+}

src/lib/os/os_test.go

@@ -205,3 +205,97 @@ func TestReaddirnamesOneAtATime(t *testing.T) {
 	}
 }
 
+func TestHardLink(t *testing.T) {
+	from, to := "hardlinktestfrom", "hardlinktestto";
+	Remove(from); // Just in case.
+	file, err := Open(to, O_CREAT | O_WRONLY, 0666);
+	if err != nil {
+		t.Fatalf("open %q failed: %v", to, err);
+	}
+	defer Remove(to);
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", to, err);
+	}
+	err = Link(to, from);
+	if err != nil {
+		t.Fatalf("link %q, %q failed: %v", to, from, err);
+	}
+	defer Remove(from);
+	tostat, err := Stat(to);
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err);
+	}
+	fromstat, err := Stat(from);
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err);
+	}
+	if tostat.Dev != fromstat.Dev || tostat.Ino != fromstat.Ino {
+		t.Errorf("link %q, %q did not create hard link", to, from);
+	}
+}
+
+func TestSymLink(t *testing.T) {
+	from, to := "symlinktestfrom", "symlinktestto";
+	Remove(from); // Just in case.
+	file, err := Open(to, O_CREAT | O_WRONLY, 0666);
+	if err != nil {
+		t.Fatalf("open %q failed: %v", to, err);
+	}
+	defer Remove(to);
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", to, err);
+	}
+	err = Symlink(to, from);
+	if err != nil {
+		t.Fatalf("symlink %q, %q failed: %v", to, from, err);
+	}
+	defer Remove(from);
+	tostat, err := Stat(to);
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err);
+	}
+	fromstat, err := Stat(from);
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err);
+	}
+	if tostat.Dev != fromstat.Dev || tostat.Ino != fromstat.Ino {
+		t.Errorf("symlink %q, %q did not create symlink", to, from);
+	}
+	fromstat, err = Lstat(from);
+	if err != nil {
+		t.Fatalf("lstat %q failed: %v", from, err);
+	}
+	if !fromstat.IsSymlink() {
+		t.Fatalf("symlink %q, %q did not create symlink", to, from);
+	}
+	s, err := Readlink(from);
+	if err != nil {
+		t.Fatalf("readlink %q failed: %v", from, err);
+	}
+	if s != to {
+		t.Fatalf("after symlink %q != %q", s, to);
+	}
+	file, err = Open(from, O_RDONLY, 0);
+	if err != nil {
+		t.Fatalf("open %q failed: %v", from, err);
+	}
+	file.Close();
+}
+
+func TestLongSymlink(t *testing.T) {
+	s := "0123456789abcdef";
+	s = s + s + s + s + s + s + s + s + s + s + s + s + s + s + s + s + s;
+	from := "longsymlinktestfrom";
+	err := Symlink(s, from);
+	if err != nil {
+		t.Fatalf("symlink %q, %q failed: %v", s, from, err);
+	}
+	defer Remove(from);
+	r, err := Readlink(from);
+	if err != nil {
+		t.Fatalf("readlink %q failed: %v", from, err);
+	}
+	if r != s {
+		t.Fatalf("after symlink %q != %q", r, s);
+	}
+}

src/lib/syscall/file_darwin.go

@@ -110,3 +110,23 @@ func Chdir(dir string) (ret int64, errno int64) {
 	r1, r2, err := Syscall(SYS_CHDIR, int64(uintptr(unsafe.Pointer(namebuf))), 0, 0);
 	return r1, err;
 }
+
+func Link(oldpath, newpath string) (ret int64, errno int64) {
+	oldbuf := StringBytePtr(oldpath);
+	newbuf := StringBytePtr(newpath);
+	r1, r2, err := Syscall(SYS_LINK, int64(uintptr(unsafe.Pointer(oldbuf))), int64(uintptr(unsafe.Pointer(newbuf))), 0);
+	return r1, err;
+}
+
+func Symlink(oldpath, newpath string) (ret int64, errno int64) {
+	oldbuf := StringBytePtr(oldpath);
+	newbuf := StringBytePtr(newpath);
+	r1, r2, err := Syscall(SYS_SYMLINK, int64(uintptr(unsafe.Pointer(oldbuf))), int64(uintptr(unsafe.Pointer(newbuf))), 0);
+	return r1, err;
+}
+
+func Readlink(path string, buf *byte, nbytes int64) (ret int64, errno int64) {
+	pathbuf := StringBytePtr(path);
+	r1, r2, err := Syscall(SYS_READLINK, int64(uintptr(unsafe.Pointer(pathbuf))), int64(uintptr(unsafe.Pointer(buf))), nbytes);
+	return r1, err;
+}

src/lib/syscall/file_linux.go

@@ -111,3 +111,23 @@ func Chdir(dir string) (ret int64, errno int64) {
 	r1, r2, err := Syscall(SYS_CHDIR, int64(uintptr(unsafe.Pointer(namebuf))), 0, 0);
 	return r1, err;
 }
+
+func Link(oldpath, newpath string) (ret int64, errno int64) {
+	oldbuf := StringBytePtr(oldpath);
+	newbuf := StringBytePtr(newpath);
+	r1, r2, err := Syscall(SYS_LINK, int64(uintptr(unsafe.Pointer(oldbuf))), int64(uintptr(unsafe.Pointer(newbuf))), 0);
+	return r1, err;
+}
+
+func Symlink(oldpath, newpath string) (ret int64, errno int64) {
+	oldbuf := StringBytePtr(oldpath);
+	newbuf := StringBytePtr(newpath);
+	r1, r2, err := Syscall(SYS_SYMLINK, int64(uintptr(unsafe.Pointer(oldbuf))), int64(uintptr(unsafe.Pointer(newbuf))), 0);
+	return r1, err;
+}
+
+func Readlink(path string, buf *byte, nbytes int64) (ret int64, errno int64) {
+	pathbuf := StringBytePtr(path);
+	r1, r2, err := Syscall(SYS_READLINK, int64(uintptr(unsafe.Pointer(pathbuf))), int64(uintptr(unsafe.Pointer(buf))), nbytes);
+	return r1, err;
+}