// 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
}
