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package dbus
import (
"encoding/binary"
"io"
"reflect"
)
type decoder struct {
in io.Reader
order binary.ByteOrder
pos int
}
// newDecoder returns a new decoder that reads values from in. The input is
// expected to be in the given byte order.
func newDecoder(in io.Reader, order binary.ByteOrder) *decoder {
dec := new(decoder)
dec.in = in
dec.order = order
return dec
}
// align aligns the input to the given boundary and panics on error.
func (dec *decoder) align(n int) {
if dec.pos%n != 0 {
newpos := (dec.pos + n - 1) & ^(n - 1)
empty := make([]byte, newpos-dec.pos)
if _, err := io.ReadFull(dec.in, empty); err != nil {
panic(err)
}
dec.pos = newpos
}
}
// Calls binary.Read(dec.in, dec.order, v) and panics on read errors.
func (dec *decoder) binread(v interface{}) {
if err := binary.Read(dec.in, dec.order, v); err != nil {
panic(err)
}
}
func (dec *decoder) Decode(sig Signature) (vs []interface{}, err error) {
defer func() {
var ok bool
v := recover()
if err, ok = v.(error); ok {
if err == io.EOF || err == io.ErrUnexpectedEOF {
err = FormatError("unexpected EOF")
}
}
}()
vs = make([]interface{}, 0)
s := sig.str
for s != "" {
err, rem := validSingle(s, 0)
if err != nil {
return nil, err
}
v := dec.decode(s[:len(s)-len(rem)], 0)
vs = append(vs, v)
s = rem
}
return vs, nil
}
func (dec *decoder) decode(s string, depth int) interface{} {
dec.align(alignment(typeFor(s)))
switch s[0] {
case 'y':
var b [1]byte
if _, err := dec.in.Read(b[:]); err != nil {
panic(err)
}
dec.pos++
return b[0]
case 'b':
i := dec.decode("u", depth).(uint32)
switch {
case i == 0:
return false
case i == 1:
return true
default:
panic(FormatError("invalid value for boolean"))
}
case 'n':
var i int16
dec.binread(&i)
dec.pos += 2
return i
case 'i':
var i int32
dec.binread(&i)
dec.pos += 4
return i
case 'x':
var i int64
dec.binread(&i)
dec.pos += 8
return i
case 'q':
var i uint16
dec.binread(&i)
dec.pos += 2
return i
case 'u':
var i uint32
dec.binread(&i)
dec.pos += 4
return i
case 't':
var i uint64
dec.binread(&i)
dec.pos += 8
return i
case 'd':
var f float64
dec.binread(&f)
dec.pos += 8
return f
case 's':
length := dec.decode("u", depth).(uint32)
b := make([]byte, int(length)+1)
if _, err := io.ReadFull(dec.in, b); err != nil {
panic(err)
}
dec.pos += int(length) + 1
return string(b[:len(b)-1])
case 'o':
return ObjectPath(dec.decode("s", depth).(string))
case 'g':
length := dec.decode("y", depth).(byte)
b := make([]byte, int(length)+1)
if _, err := io.ReadFull(dec.in, b); err != nil {
panic(err)
}
dec.pos += int(length) + 1
sig, err := ParseSignature(string(b[:len(b)-1]))
if err != nil {
panic(err)
}
return sig
case 'v':
if depth >= 64 {
panic(FormatError("input exceeds container depth limit"))
}
var variant Variant
sig := dec.decode("g", depth).(Signature)
if len(sig.str) == 0 {
panic(FormatError("variant signature is empty"))
}
err, rem := validSingle(sig.str, 0)
if err != nil {
panic(err)
}
if rem != "" {
panic(FormatError("variant signature has multiple types"))
}
variant.sig = sig
variant.value = dec.decode(sig.str, depth+1)
return variant
case 'h':
return UnixFDIndex(dec.decode("u", depth).(uint32))
case 'a':
if len(s) > 1 && s[1] == '{' {
ksig := s[2:3]
vsig := s[3 : len(s)-1]
v := reflect.MakeMap(reflect.MapOf(typeFor(ksig), typeFor(vsig)))
if depth >= 63 {
panic(FormatError("input exceeds container depth limit"))
}
length := dec.decode("u", depth).(uint32)
// Even for empty maps, the correct padding must be included
dec.align(8)
spos := dec.pos
for dec.pos < spos+int(length) {
dec.align(8)
if !isKeyType(v.Type().Key()) {
panic(InvalidTypeError{v.Type()})
}
kv := dec.decode(ksig, depth+2)
vv := dec.decode(vsig, depth+2)
v.SetMapIndex(reflect.ValueOf(kv), reflect.ValueOf(vv))
}
return v.Interface()
}
if depth >= 64 {
panic(FormatError("input exceeds container depth limit"))
}
sig := s[1:]
length := dec.decode("u", depth).(uint32)
// capacity can be determined only for fixed-size element types
var capacity int
if s := sigByteSize(sig); s != 0 {
capacity = int(length) / s
}
v := reflect.MakeSlice(reflect.SliceOf(typeFor(sig)), 0, capacity)
// Even for empty arrays, the correct padding must be included
align := alignment(typeFor(s[1:]))
if len(s) > 1 && s[1] == '(' {
//Special case for arrays of structs
//structs decode as a slice of interface{} values
//but the dbus alignment does not match this
align = 8
}
dec.align(align)
spos := dec.pos
for dec.pos < spos+int(length) {
ev := dec.decode(s[1:], depth+1)
v = reflect.Append(v, reflect.ValueOf(ev))
}
return v.Interface()
case '(':
if depth >= 64 {
panic(FormatError("input exceeds container depth limit"))
}
dec.align(8)
v := make([]interface{}, 0)
s = s[1 : len(s)-1]
for s != "" {
err, rem := validSingle(s, 0)
if err != nil {
panic(err)
}
ev := dec.decode(s[:len(s)-len(rem)], depth+1)
v = append(v, ev)
s = rem
}
return v
default:
panic(SignatureError{Sig: s})
}
}
// sigByteSize tries to calculates size of the given signature in bytes.
//
// It returns zero when it can't, for example when it contains non-fixed size
// types such as strings, maps and arrays that require reading of the transmitted
// data, for that we would need to implement the unread method for Decoder first.
func sigByteSize(sig string) int {
var total int
for offset := 0; offset < len(sig); {
switch sig[offset] {
case 'y':
total += 1
offset += 1
case 'n', 'q':
total += 2
offset += 1
case 'b', 'i', 'u', 'h':
total += 4
offset += 1
case 'x', 't', 'd':
total += 8
offset += 1
case '(':
i := 1
depth := 1
for i < len(sig[offset:]) && depth != 0 {
if sig[offset+i] == '(' {
depth++
} else if sig[offset+i] == ')' {
depth--
}
i++
}
s := sigByteSize(sig[offset+1 : offset+i-1])
if s == 0 {
return 0
}
total += s
offset += i
default:
return 0
}
}
return total
}
// A FormatError is an error in the wire format.
type FormatError string
func (e FormatError) Error() string {
return "dbus: wire format error: " + string(e)
}
|
