1 files changed, 554 insertions, 0 deletions
diff --git a/src/syscall/fs_js.go b/src/syscall/fs_js.go
new file mode 100644
index 0000000..673feea
--- /dev/null
+++ b/src/syscall/fs_js.go
@@ -0,0 +1,554 @@
+// Copyright 2018 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.
+
+// +build js,wasm
+
+package syscall
+
+import (
+	"errors"
+	"sync"
+	"syscall/js"
+)
+
+// Provided by package runtime.
+func now() (sec int64, nsec int32)
+
+var jsProcess = js.Global().Get("process")
+var jsFS = js.Global().Get("fs")
+var constants = jsFS.Get("constants")
+
+var uint8Array = js.Global().Get("Uint8Array")
+
+var (
+	nodeWRONLY = constants.Get("O_WRONLY").Int()
+	nodeRDWR   = constants.Get("O_RDWR").Int()
+	nodeCREATE = constants.Get("O_CREAT").Int()
+	nodeTRUNC  = constants.Get("O_TRUNC").Int()
+	nodeAPPEND = constants.Get("O_APPEND").Int()
+	nodeEXCL   = constants.Get("O_EXCL").Int()
+)
+
+type jsFile struct {
+	path    string
+	entries []string
+	dirIdx  int // entries[:dirIdx] have already been returned in ReadDirent
+	pos     int64
+	seeked  bool
+}
+
+var filesMu sync.Mutex
+var files = map[int]*jsFile{
+	0: {},
+	1: {},
+	2: {},
+}
+
+func fdToFile(fd int) (*jsFile, error) {
+	filesMu.Lock()
+	f, ok := files[fd]
+	filesMu.Unlock()
+	if !ok {
+		return nil, EBADF
+	}
+	return f, nil
+}
+
+func Open(path string, openmode int, perm uint32) (int, error) {
+	if err := checkPath(path); err != nil {
+		return 0, err
+	}
+
+	flags := 0
+	if openmode&O_WRONLY != 0 {
+		flags |= nodeWRONLY
+	}
+	if openmode&O_RDWR != 0 {
+		flags |= nodeRDWR
+	}
+	if openmode&O_CREATE != 0 {
+		flags |= nodeCREATE
+	}
+	if openmode&O_TRUNC != 0 {
+		flags |= nodeTRUNC
+	}
+	if openmode&O_APPEND != 0 {
+		flags |= nodeAPPEND
+	}
+	if openmode&O_EXCL != 0 {
+		flags |= nodeEXCL
+	}
+	if openmode&O_SYNC != 0 {
+		return 0, errors.New("syscall.Open: O_SYNC is not supported by js/wasm")
+	}
+
+	jsFD, err := fsCall("open", path, flags, perm)
+	if err != nil {
+		return 0, err
+	}
+	fd := jsFD.Int()
+
+	var entries []string
+	if stat, err := fsCall("fstat", fd); err == nil && stat.Call("isDirectory").Bool() {
+		dir, err := fsCall("readdir", path)
+		if err != nil {
+			return 0, err
+		}
+		entries = make([]string, dir.Length())
+		for i := range entries {
+			entries[i] = dir.Index(i).String()
+		}
+	}
+
+	if path[0] != '/' {
+		cwd := jsProcess.Call("cwd").String()
+		path = cwd + "/" + path
+	}
+	f := &jsFile{
+		path:    path,
+		entries: entries,
+	}
+	filesMu.Lock()
+	files[fd] = f
+	filesMu.Unlock()
+	return fd, nil
+}
+
+func Close(fd int) error {
+	filesMu.Lock()
+	delete(files, fd)
+	filesMu.Unlock()
+	_, err := fsCall("close", fd)
+	return err
+}
+
+func CloseOnExec(fd int) {
+	// nothing to do - no exec
+}
+
+func Mkdir(path string, perm uint32) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("mkdir", path, perm)
+	return err
+}
+
+func ReadDirent(fd int, buf []byte) (int, error) {
+	f, err := fdToFile(fd)
+	if err != nil {
+		return 0, err
+	}
+	if f.entries == nil {
+		return 0, EINVAL
+	}
+
+	n := 0
+	for f.dirIdx < len(f.entries) {
+		entry := f.entries[f.dirIdx]
+		l := 2 + len(entry)
+		if l > len(buf) {
+			break
+		}
+		buf[0] = byte(l)
+		buf[1] = byte(l >> 8)
+		copy(buf[2:], entry)
+		buf = buf[l:]
+		n += l
+		f.dirIdx++
+	}
+
+	return n, nil
+}
+
+func setStat(st *Stat_t, jsSt js.Value) {
+	st.Dev = int64(jsSt.Get("dev").Int())
+	st.Ino = uint64(jsSt.Get("ino").Int())
+	st.Mode = uint32(jsSt.Get("mode").Int())
+	st.Nlink = uint32(jsSt.Get("nlink").Int())
+	st.Uid = uint32(jsSt.Get("uid").Int())
+	st.Gid = uint32(jsSt.Get("gid").Int())
+	st.Rdev = int64(jsSt.Get("rdev").Int())
+	st.Size = int64(jsSt.Get("size").Int())
+	st.Blksize = int32(jsSt.Get("blksize").Int())
+	st.Blocks = int32(jsSt.Get("blocks").Int())
+	atime := int64(jsSt.Get("atimeMs").Int())
+	st.Atime = atime / 1000
+	st.AtimeNsec = (atime % 1000) * 1000000
+	mtime := int64(jsSt.Get("mtimeMs").Int())
+	st.Mtime = mtime / 1000
+	st.MtimeNsec = (mtime % 1000) * 1000000
+	ctime := int64(jsSt.Get("ctimeMs").Int())
+	st.Ctime = ctime / 1000
+	st.CtimeNsec = (ctime % 1000) * 1000000
+}
+
+func Stat(path string, st *Stat_t) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	jsSt, err := fsCall("stat", path)
+	if err != nil {
+		return err
+	}
+	setStat(st, jsSt)
+	return nil
+}
+
+func Lstat(path string, st *Stat_t) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	jsSt, err := fsCall("lstat", path)
+	if err != nil {
+		return err
+	}
+	setStat(st, jsSt)
+	return nil
+}
+
+func Fstat(fd int, st *Stat_t) error {
+	jsSt, err := fsCall("fstat", fd)
+	if err != nil {
+		return err
+	}
+	setStat(st, jsSt)
+	return nil
+}
+
+func Unlink(path string) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("unlink", path)
+	return err
+}
+
+func Rmdir(path string) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("rmdir", path)
+	return err
+}
+
+func Chmod(path string, mode uint32) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("chmod", path, mode)
+	return err
+}
+
+func Fchmod(fd int, mode uint32) error {
+	_, err := fsCall("fchmod", fd, mode)
+	return err
+}
+
+func Chown(path string, uid, gid int) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("chown", path, uint32(uid), uint32(gid))
+	return err
+}
+
+func Fchown(fd int, uid, gid int) error {
+	_, err := fsCall("fchown", fd, uint32(uid), uint32(gid))
+	return err
+}
+
+func Lchown(path string, uid, gid int) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	if jsFS.Get("lchown").IsUndefined() {
+		// fs.lchown is unavailable on Linux until Node.js 10.6.0
+		// TODO(neelance): remove when we require at least this Node.js version
+		return ENOSYS
+	}
+	_, err := fsCall("lchown", path, uint32(uid), uint32(gid))
+	return err
+}
+
+func UtimesNano(path string, ts []Timespec) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	if len(ts) != 2 {
+		return EINVAL
+	}
+	atime := ts[0].Sec
+	mtime := ts[1].Sec
+	_, err := fsCall("utimes", path, atime, mtime)
+	return err
+}
+
+func Rename(from, to string) error {
+	if err := checkPath(from); err != nil {
+		return err
+	}
+	if err := checkPath(to); err != nil {
+		return err
+	}
+	_, err := fsCall("rename", from, to)
+	return err
+}
+
+func Truncate(path string, length int64) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	_, err := fsCall("truncate", path, length)
+	return err
+}
+
+func Ftruncate(fd int, length int64) error {
+	_, err := fsCall("ftruncate", fd, length)
+	return err
+}
+
+func Getcwd(buf []byte) (n int, err error) {
+	defer recoverErr(&err)
+	cwd := jsProcess.Call("cwd").String()
+	n = copy(buf, cwd)
+	return
+}
+
+func Chdir(path string) (err error) {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	defer recoverErr(&err)
+	jsProcess.Call("chdir", path)
+	return
+}
+
+func Fchdir(fd int) error {
+	f, err := fdToFile(fd)
+	if err != nil {
+		return err
+	}
+	return Chdir(f.path)
+}
+
+func Readlink(path string, buf []byte) (n int, err error) {
+	if err := checkPath(path); err != nil {
+		return 0, err
+	}
+	dst, err := fsCall("readlink", path)
+	if err != nil {
+		return 0, err
+	}
+	n = copy(buf, dst.String())
+	return n, nil
+}
+
+func Link(path, link string) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	if err := checkPath(link); err != nil {
+		return err
+	}
+	_, err := fsCall("link", path, link)
+	return err
+}
+
+func Symlink(path, link string) error {
+	if err := checkPath(path); err != nil {
+		return err
+	}
+	if err := checkPath(link); err != nil {
+		return err
+	}
+	_, err := fsCall("symlink", path, link)
+	return err
+}
+
+func Fsync(fd int) error {
+	_, err := fsCall("fsync", fd)
+	return err
+}
+
+func Read(fd int, b []byte) (int, error) {
+	f, err := fdToFile(fd)
+	if err != nil {
+		return 0, err
+	}
+
+	if f.seeked {
+		n, err := Pread(fd, b, f.pos)
+		f.pos += int64(n)
+		return n, err
+	}
+
+	buf := uint8Array.New(len(b))
+	n, err := fsCall("read", fd, buf, 0, len(b), nil)
+	if err != nil {
+		return 0, err
+	}
+	js.CopyBytesToGo(b, buf)
+
+	n2 := n.Int()
+	f.pos += int64(n2)
+	return n2, err
+}
+
+func Write(fd int, b []byte) (int, error) {
+	f, err := fdToFile(fd)
+	if err != nil {
+		return 0, err
+	}
+
+	if f.seeked {
+		n, err := Pwrite(fd, b, f.pos)
+		f.pos += int64(n)
+		return n, err
+	}
+
+	if faketime && (fd == 1 || fd == 2) {
+		n := faketimeWrite(fd, b)
+		if n < 0 {
+			return 0, errnoErr(Errno(-n))
+		}
+		return n, nil
+	}
+
+	buf := uint8Array.New(len(b))
+	js.CopyBytesToJS(buf, b)
+	n, err := fsCall("write", fd, buf, 0, len(b), nil)
+	if err != nil {
+		return 0, err
+	}
+	n2 := n.Int()
+	f.pos += int64(n2)
+	return n2, err
+}
+
+func Pread(fd int, b []byte, offset int64) (int, error) {
+	buf := uint8Array.New(len(b))
+	n, err := fsCall("read", fd, buf, 0, len(b), offset)
+	if err != nil {
+		return 0, err
+	}
+	js.CopyBytesToGo(b, buf)
+	return n.Int(), nil
+}
+
+func Pwrite(fd int, b []byte, offset int64) (int, error) {
+	buf := uint8Array.New(len(b))
+	js.CopyBytesToJS(buf, b)
+	n, err := fsCall("write", fd, buf, 0, len(b), offset)
+	if err != nil {
+		return 0, err
+	}
+	return n.Int(), nil
+}
+
+func Seek(fd int, offset int64, whence int) (int64, error) {
+	f, err := fdToFile(fd)
+	if err != nil {
+		return 0, err
+	}
+
+	var newPos int64
+	switch whence {
+	case 0:
+		newPos = offset
+	case 1:
+		newPos = f.pos + offset
+	case 2:
+		var st Stat_t
+		if err := Fstat(fd, &st); err != nil {
+			return 0, err
+		}
+		newPos = st.Size + offset
+	default:
+		return 0, errnoErr(EINVAL)
+	}
+
+	if newPos < 0 {
+		return 0, errnoErr(EINVAL)
+	}
+
+	f.seeked = true
+	f.dirIdx = 0 // Reset directory read position. See issue 35767.
+	f.pos = newPos
+	return newPos, nil
+}
+
+func Dup(fd int) (int, error) {
+	return 0, ENOSYS
+}
+
+func Dup2(fd, newfd int) error {
+	return ENOSYS
+}
+
+func Pipe(fd []int) error {
+	return ENOSYS
+}
+
+func fsCall(name string, args ...interface{}) (js.Value, error) {
+	type callResult struct {
+		val js.Value
+		err error
+	}
+
+	c := make(chan callResult, 1)
+	f := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		var res callResult
+
+		if len(args) >= 1 { // on Node.js 8, fs.utimes calls the callback without any arguments
+			if jsErr := args[0]; !jsErr.IsNull() {
+				res.err = mapJSError(jsErr)
+			}
+		}
+
+		res.val = js.Undefined()
+		if len(args) >= 2 {
+			res.val = args[1]
+		}
+
+		c <- res
+		return nil
+	})
+	defer f.Release()
+	jsFS.Call(name, append(args, f)...)
+	res := <-c
+	return res.val, res.err
+}
+
+// checkPath checks that the path is not empty and that it contains no null characters.
+func checkPath(path string) error {
+	if path == "" {
+		return EINVAL
+	}
+	for i := 0; i < len(path); i++ {
+		if path[i] == '\x00' {
+			return EINVAL
+		}
+	}
+	return nil
+}
+
+func recoverErr(errPtr *error) {
+	if err := recover(); err != nil {
+		jsErr, ok := err.(js.Error)
+		if !ok {
+			panic(err)
+		}
+		*errPtr = mapJSError(jsErr.Value)
+	}
+}
+
+// mapJSError maps an error given by Node.js to the appropriate Go error
+func mapJSError(jsErr js.Value) error {
+	errno, ok := errnoByCode[jsErr.Get("code").String()]
+	if !ok {
+		panic(jsErr)
+	}
+	return errnoErr(Errno(errno))
+}