--- /dev/null
+// 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
+}
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