diff --git a/vendor/golang.org/x/sys/plan9/dir_plan9.go b/vendor/golang.org/x/sys/plan9/dir_plan9.go
new file mode 100644
index 0000000..0955e0c
--- /dev/null
+++ b/vendor/golang.org/x/sys/plan9/dir_plan9.go
@@ -0,0 +1,212 @@
+// Copyright 2012 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.
+
+// Plan 9 directory marshalling. See intro(5).
+
+package plan9
+
+import "errors"
+
+var (
+	ErrShortStat = errors.New("stat buffer too short")
+	ErrBadStat   = errors.New("malformed stat buffer")
+	ErrBadName   = errors.New("bad character in file name")
+)
+
+// A Qid represents a 9P server's unique identification for a file.
+type Qid struct {
+	Path uint64 // the file server's unique identification for the file
+	Vers uint32 // version number for given Path
+	Type uint8  // the type of the file (plan9.QTDIR for example)
+}
+
+// A Dir contains the metadata for a file.
+type Dir struct {
+	// system-modified data
+	Type uint16 // server type
+	Dev  uint32 // server subtype
+
+	// file data
+	Qid    Qid    // unique id from server
+	Mode   uint32 // permissions
+	Atime  uint32 // last read time
+	Mtime  uint32 // last write time
+	Length int64  // file length
+	Name   string // last element of path
+	Uid    string // owner name
+	Gid    string // group name
+	Muid   string // last modifier name
+}
+
+var nullDir = Dir{
+	Type: ^uint16(0),
+	Dev:  ^uint32(0),
+	Qid: Qid{
+		Path: ^uint64(0),
+		Vers: ^uint32(0),
+		Type: ^uint8(0),
+	},
+	Mode:   ^uint32(0),
+	Atime:  ^uint32(0),
+	Mtime:  ^uint32(0),
+	Length: ^int64(0),
+}
+
+// Null assigns special "don't touch" values to members of d to
+// avoid modifying them during plan9.Wstat.
+func (d *Dir) Null() { *d = nullDir }
+
+// Marshal encodes a 9P stat message corresponding to d into b
+//
+// If there isn't enough space in b for a stat message, ErrShortStat is returned.
+func (d *Dir) Marshal(b []byte) (n int, err error) {
+	n = STATFIXLEN + len(d.Name) + len(d.Uid) + len(d.Gid) + len(d.Muid)
+	if n > len(b) {
+		return n, ErrShortStat
+	}
+
+	for _, c := range d.Name {
+		if c == '/' {
+			return n, ErrBadName
+		}
+	}
+
+	b = pbit16(b, uint16(n)-2)
+	b = pbit16(b, d.Type)
+	b = pbit32(b, d.Dev)
+	b = pbit8(b, d.Qid.Type)
+	b = pbit32(b, d.Qid.Vers)
+	b = pbit64(b, d.Qid.Path)
+	b = pbit32(b, d.Mode)
+	b = pbit32(b, d.Atime)
+	b = pbit32(b, d.Mtime)
+	b = pbit64(b, uint64(d.Length))
+	b = pstring(b, d.Name)
+	b = pstring(b, d.Uid)
+	b = pstring(b, d.Gid)
+	b = pstring(b, d.Muid)
+
+	return n, nil
+}
+
+// UnmarshalDir decodes a single 9P stat message from b and returns the resulting Dir.
+//
+// If b is too small to hold a valid stat message, ErrShortStat is returned.
+//
+// If the stat message itself is invalid, ErrBadStat is returned.
+func UnmarshalDir(b []byte) (*Dir, error) {
+	if len(b) < STATFIXLEN {
+		return nil, ErrShortStat
+	}
+	size, buf := gbit16(b)
+	if len(b) != int(size)+2 {
+		return nil, ErrBadStat
+	}
+	b = buf
+
+	var d Dir
+	d.Type, b = gbit16(b)
+	d.Dev, b = gbit32(b)
+	d.Qid.Type, b = gbit8(b)
+	d.Qid.Vers, b = gbit32(b)
+	d.Qid.Path, b = gbit64(b)
+	d.Mode, b = gbit32(b)
+	d.Atime, b = gbit32(b)
+	d.Mtime, b = gbit32(b)
+
+	n, b := gbit64(b)
+	d.Length = int64(n)
+
+	var ok bool
+	if d.Name, b, ok = gstring(b); !ok {
+		return nil, ErrBadStat
+	}
+	if d.Uid, b, ok = gstring(b); !ok {
+		return nil, ErrBadStat
+	}
+	if d.Gid, b, ok = gstring(b); !ok {
+		return nil, ErrBadStat
+	}
+	if d.Muid, b, ok = gstring(b); !ok {
+		return nil, ErrBadStat
+	}
+
+	return &d, nil
+}
+
+// pbit8 copies the 8-bit number v to b and returns the remaining slice of b.
+func pbit8(b []byte, v uint8) []byte {
+	b[0] = byte(v)
+	return b[1:]
+}
+
+// pbit16 copies the 16-bit number v to b in little-endian order and returns the remaining slice of b.
+func pbit16(b []byte, v uint16) []byte {
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	return b[2:]
+}
+
+// pbit32 copies the 32-bit number v to b in little-endian order and returns the remaining slice of b.
+func pbit32(b []byte, v uint32) []byte {
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+	return b[4:]
+}
+
+// pbit64 copies the 64-bit number v to b in little-endian order and returns the remaining slice of b.
+func pbit64(b []byte, v uint64) []byte {
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+	b[4] = byte(v >> 32)
+	b[5] = byte(v >> 40)
+	b[6] = byte(v >> 48)
+	b[7] = byte(v >> 56)
+	return b[8:]
+}
+
+// pstring copies the string s to b, prepending it with a 16-bit length in little-endian order, and
+// returning the remaining slice of b..
+func pstring(b []byte, s string) []byte {
+	b = pbit16(b, uint16(len(s)))
+	n := copy(b, s)
+	return b[n:]
+}
+
+// gbit8 reads an 8-bit number from b and returns it with the remaining slice of b.
+func gbit8(b []byte) (uint8, []byte) {
+	return uint8(b[0]), b[1:]
+}
+
+// gbit16 reads a 16-bit number in little-endian order from b and returns it with the remaining slice of b.
+func gbit16(b []byte) (uint16, []byte) {
+	return uint16(b[0]) | uint16(b[1])<<8, b[2:]
+}
+
+// gbit32 reads a 32-bit number in little-endian order from b and returns it with the remaining slice of b.
+func gbit32(b []byte) (uint32, []byte) {
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24, b[4:]
+}
+
+// gbit64 reads a 64-bit number in little-endian order from b and returns it with the remaining slice of b.
+func gbit64(b []byte) (uint64, []byte) {
+	lo := uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+	hi := uint32(b[4]) | uint32(b[5])<<8 | uint32(b[6])<<16 | uint32(b[7])<<24
+	return uint64(lo) | uint64(hi)<<32, b[8:]
+}
+
+// gstring reads a string from b, prefixed with a 16-bit length in little-endian order.
+// It returns the string with the remaining slice of b and a boolean. If the length is
+// greater than the number of bytes in b, the boolean will be false.
+func gstring(b []byte) (string, []byte, bool) {
+	n, b := gbit16(b)
+	if int(n) > len(b) {
+		return "", b, false
+	}
+	return string(b[:n]), b[n:], true
+}