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package dbus
import (
"bytes"
"encoding/binary"
"io"
"reflect"
)
// An encoder encodes values to the D-Bus wire format.
type encoder struct {
out io.Writer
order binary.ByteOrder
pos int
}
// NewEncoder returns a new encoder that writes to out in the given byte order.
func newEncoder(out io.Writer, order binary.ByteOrder) *encoder {
return newEncoderAtOffset(out, 0, order)
}
// newEncoderAtOffset returns a new encoder that writes to out in the given
// byte order. Specify the offset to initialize pos for proper alignment
// computation.
func newEncoderAtOffset(out io.Writer, offset int, order binary.ByteOrder) *encoder {
enc := new(encoder)
enc.out = out
enc.order = order
enc.pos = offset
return enc
}
// Aligns the next output to be on a multiple of n. Panics on write errors.
func (enc *encoder) align(n int) {
pad := enc.padding(0, n)
if pad > 0 {
empty := make([]byte, pad)
if _, err := enc.out.Write(empty); err != nil {
panic(err)
}
enc.pos += pad
}
}
// pad returns the number of bytes of padding, based on current position and additional offset.
// and alignment.
func (enc *encoder) padding(offset, algn int) int {
abs := enc.pos + offset
if abs%algn != 0 {
newabs := (abs + algn - 1) & ^(algn - 1)
return newabs - abs
}
return 0
}
// Calls binary.Write(enc.out, enc.order, v) and panics on write errors.
func (enc *encoder) binwrite(v interface{}) {
if err := binary.Write(enc.out, enc.order, v); err != nil {
panic(err)
}
}
// Encode encodes the given values to the underlying reader. All written values
// are aligned properly as required by the D-Bus spec.
func (enc *encoder) Encode(vs ...interface{}) (err error) {
defer func() {
err, _ = recover().(error)
}()
for _, v := range vs {
enc.encode(reflect.ValueOf(v), 0)
}
return nil
}
// encode encodes the given value to the writer and panics on error. depth holds
// the depth of the container nesting.
func (enc *encoder) encode(v reflect.Value, depth int) {
enc.align(alignment(v.Type()))
switch v.Kind() {
case reflect.Uint8:
var b [1]byte
b[0] = byte(v.Uint())
if _, err := enc.out.Write(b[:]); err != nil {
panic(err)
}
enc.pos++
case reflect.Bool:
if v.Bool() {
enc.encode(reflect.ValueOf(uint32(1)), depth)
} else {
enc.encode(reflect.ValueOf(uint32(0)), depth)
}
case reflect.Int16:
enc.binwrite(int16(v.Int()))
enc.pos += 2
case reflect.Uint16:
enc.binwrite(uint16(v.Uint()))
enc.pos += 2
case reflect.Int, reflect.Int32:
enc.binwrite(int32(v.Int()))
enc.pos += 4
case reflect.Uint, reflect.Uint32:
enc.binwrite(uint32(v.Uint()))
enc.pos += 4
case reflect.Int64:
enc.binwrite(v.Int())
enc.pos += 8
case reflect.Uint64:
enc.binwrite(v.Uint())
enc.pos += 8
case reflect.Float64:
enc.binwrite(v.Float())
enc.pos += 8
case reflect.String:
enc.encode(reflect.ValueOf(uint32(len(v.String()))), depth)
b := make([]byte, v.Len()+1)
copy(b, v.String())
b[len(b)-1] = 0
n, err := enc.out.Write(b)
if err != nil {
panic(err)
}
enc.pos += n
case reflect.Ptr:
enc.encode(v.Elem(), depth)
case reflect.Slice, reflect.Array:
if depth >= 64 {
panic(FormatError("input exceeds container depth limit"))
}
// Lookahead offset: 4 bytes for uint32 length (with alignment),
// plus alignment for elements.
n := enc.padding(0, 4) + 4
offset := enc.pos + n + enc.padding(n, alignment(v.Type().Elem()))
var buf bytes.Buffer
bufenc := newEncoderAtOffset(&buf, offset, enc.order)
for i := 0; i < v.Len(); i++ {
bufenc.encode(v.Index(i), depth+1)
}
enc.encode(reflect.ValueOf(uint32(buf.Len())), depth)
length := buf.Len()
enc.align(alignment(v.Type().Elem()))
if _, err := buf.WriteTo(enc.out); err != nil {
panic(err)
}
enc.pos += length
case reflect.Struct:
if depth >= 64 && v.Type() != signatureType {
panic(FormatError("input exceeds container depth limit"))
}
switch t := v.Type(); t {
case signatureType:
str := v.Field(0)
enc.encode(reflect.ValueOf(byte(str.Len())), depth+1)
b := make([]byte, str.Len()+1)
copy(b, str.String())
b[len(b)-1] = 0
n, err := enc.out.Write(b)
if err != nil {
panic(err)
}
enc.pos += n
case variantType:
variant := v.Interface().(Variant)
enc.encode(reflect.ValueOf(variant.sig), depth+1)
enc.encode(reflect.ValueOf(variant.value), depth+1)
default:
for i := 0; i < v.Type().NumField(); i++ {
field := t.Field(i)
if field.PkgPath == "" && field.Tag.Get("dbus") != "-" {
enc.encode(v.Field(i), depth+1)
}
}
}
case reflect.Map:
// Maps are arrays of structures, so they actually increase the depth by
// 2.
if depth >= 63 {
panic(FormatError("input exceeds container depth limit"))
}
if !isKeyType(v.Type().Key()) {
panic(InvalidTypeError{v.Type()})
}
keys := v.MapKeys()
// Lookahead offset: 4 bytes for uint32 length (with alignment),
// plus 8-byte alignment
n := enc.padding(0, 4) + 4
offset := enc.pos + n + enc.padding(n, 8)
var buf bytes.Buffer
bufenc := newEncoderAtOffset(&buf, offset, enc.order)
for _, k := range keys {
bufenc.align(8)
bufenc.encode(k, depth+2)
bufenc.encode(v.MapIndex(k), depth+2)
}
enc.encode(reflect.ValueOf(uint32(buf.Len())), depth)
length := buf.Len()
enc.align(8)
if _, err := buf.WriteTo(enc.out); err != nil {
panic(err)
}
enc.pos += length
case reflect.Interface:
enc.encode(reflect.ValueOf(MakeVariant(v.Interface())), depth)
default:
panic(InvalidTypeError{v.Type()})
}
}
|
