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package mtp
import (
"encoding/binary"
"fmt"
"io"
"log"
"reflect"
"strings"
"time"
"unicode/utf8"
)
var byteOrder = binary.LittleEndian
func decodeStr(r io.Reader) (string, error) {
var szSlice [1]byte
_, err := r.Read(szSlice[:])
if err != nil {
return "", err
}
sz := int(szSlice[0])
if sz == 0 {
return "", nil
}
utfStr := make([]byte, 4*sz)
data := make([]byte, 2*sz)
n, err := r.Read(data)
if err != nil {
return "", err
}
if n < len(data) {
return "", fmt.Errorf("underflow")
}
w := 0
for i := 0; i < int(2*sz); i += 2 {
cp := byteOrder.Uint16(data[i:])
w += utf8.EncodeRune(utfStr[w:], rune(cp))
}
if utfStr[w-1] == 0 {
w--
}
s := string(utfStr[:w])
return s, nil
}
func encodeStr(buf []byte, s string) ([]byte, error) {
if s == "" {
buf[0] = 0
return buf[:1], nil
}
codepoints := 0
buf = append(buf[:0], 0)
var rune [2]byte
for _, r := range s {
byteOrder.PutUint16(rune[:], uint16(r))
buf = append(buf, rune[0], rune[1])
codepoints++
}
buf = append(buf, 0, 0)
codepoints++
if codepoints > 254 {
return nil, fmt.Errorf("string too long")
}
buf[0] = byte(codepoints)
return buf, nil
}
func encodeStrField(w io.Writer, f reflect.Value) error {
out := make([]byte, 2*f.Len()+4)
enc, err := encodeStr(out, f.Interface().(string))
if err != nil {
return err
}
_, err = w.Write(enc)
return err
}
func kindSize(k reflect.Kind) int {
switch k {
case reflect.Int8:
return 1
case reflect.Int16:
return 2
case reflect.Int32:
return 4
case reflect.Int64:
return 8
case reflect.Uint8:
return 1
case reflect.Uint16:
return 2
case reflect.Uint32:
return 4
default:
panic(fmt.Sprintf("unknown kind %v", k))
}
}
var nullValue reflect.Value
func decodeArray(r io.Reader, t reflect.Type) (reflect.Value, error) {
var sz uint32
if err := binary.Read(r, byteOrder, &sz); err != nil {
return nullValue, err
}
ksz := int(kindSize(t.Elem().Kind()))
data := make([]byte, int(sz)*ksz)
_, err := r.Read(data)
if err != nil {
return nullValue, err
}
slice := reflect.MakeSlice(t, int(sz), int(sz))
for i := 0; i < int(sz); i++ {
from := data[i*ksz:]
var val uint64
switch ksz {
case 1:
val = uint64(from[0])
case 2:
val = uint64(byteOrder.Uint16(from[0:]))
case 4:
val = uint64(byteOrder.Uint32(from[0:]))
default:
panic("unimp")
}
slice.Index(i).SetUint(val)
}
return slice, nil
}
func encodeArray(w io.Writer, val reflect.Value) error {
sz := uint32(val.Len())
if err := binary.Write(w, byteOrder, &sz); err != nil {
return err
}
kind := val.Type().Elem().Kind()
ksz := 0
if kind == reflect.Interface {
log.Println("OK")
ksz = int(kindSize(val.Index(0).Elem().Kind()))
} else {
ksz = int(kindSize(kind))
}
data := make([]byte, int(sz)*ksz)
for i := 0; i < int(sz); i++ {
elt := val.Index(i)
to := data[i*ksz:]
switch kind {
case reflect.Uint8:
to[0] = byte(elt.Uint())
case reflect.Uint16:
byteOrder.PutUint16(to, uint16(elt.Uint()))
case reflect.Uint32:
byteOrder.PutUint32(to, uint32(elt.Uint()))
case reflect.Uint64:
byteOrder.PutUint64(to, uint64(elt.Uint()))
case reflect.Int8:
to[0] = byte(elt.Int())
case reflect.Int16:
byteOrder.PutUint16(to, uint16(elt.Int()))
case reflect.Int32:
byteOrder.PutUint32(to, uint32(elt.Int()))
case reflect.Int64:
byteOrder.PutUint64(to, uint64(elt.Int()))
default:
panic(fmt.Sprintf("unimplemented: encode for kind %v", kind))
}
}
_, err := w.Write(data)
return err
}
var timeType = reflect.ValueOf(time.Now()).Type()
const timeFormat = "20060102T150405"
const timeFormatNumTZ = "20060102T150405-0700"
var zeroTime = time.Time{}
func encodeTime(w io.Writer, f reflect.Value) error {
tptr := f.Addr().Interface().(*time.Time)
s := ""
if !tptr.Equal(zeroTime) {
s = tptr.Format(timeFormat)
}
out := make([]byte, 2*len(s)+3)
enc, err := encodeStr(out, s)
if err != nil {
return err
}
_, err = w.Write(enc)
return err
}
func decodeTime(r io.Reader, f reflect.Value) error {
s, err := decodeStr(r)
if err != nil {
return err
}
var t time.Time
if s != "" {
// Samsung has trailing dots.
s = strings.TrimRight(s, ".")
// Jolla Sailfish has trailing "Z".
s = strings.TrimRight(s, "Z")
t, err = time.Parse(timeFormat, s)
if err != nil {
// Nokia lumia has numTZ
t, err = time.Parse(timeFormatNumTZ, s)
if err != nil {
return err
}
}
}
f.Set(reflect.ValueOf(t))
return nil
}
func decodeField(r io.Reader, f reflect.Value, typeSelector DataTypeSelector) error {
if !f.CanAddr() {
return fmt.Errorf("canaddr false")
}
if f.Type() == timeType {
return decodeTime(r, f)
}
switch f.Kind() {
case reflect.Uint8:
fallthrough
case reflect.Uint16:
fallthrough
case reflect.Uint32:
fallthrough
case reflect.Uint64:
fallthrough
case reflect.Int64:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int16:
fallthrough
case reflect.Int8:
return binary.Read(r, byteOrder, f.Addr().Interface())
case reflect.String:
s, err := decodeStr(r)
if err != nil {
return err
}
f.SetString(s)
case reflect.Slice:
sl, err := decodeArray(r, f.Type())
if err != nil {
return err
}
f.Set(sl)
case reflect.Interface:
val := InstantiateType(typeSelector)
decodeField(r, val, typeSelector)
f.Set(val)
default:
panic(fmt.Sprintf("unimplemented kind %v", f))
}
return nil
}
func encodeField(w io.Writer, f reflect.Value) error {
if f.Type() == timeType {
return encodeTime(w, f)
}
switch f.Kind() {
case reflect.Uint8:
fallthrough
case reflect.Uint16:
fallthrough
case reflect.Uint32:
fallthrough
case reflect.Uint64:
fallthrough
case reflect.Int64:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int16:
fallthrough
case reflect.Int8:
return binary.Write(w, byteOrder, f.Interface())
case reflect.String:
return encodeStrField(w, f)
case reflect.Slice:
return encodeArray(w, f)
case reflect.Interface:
return encodeField(w, f.Elem())
default:
panic(fmt.Sprintf("unimplemented kind %v", f))
}
}
// Decode MTP data stream into data structure.
func Decode(r io.Reader, iface interface{}) error {
decoder, ok := iface.(Decoder)
if ok {
return decoder.Decode(r)
}
typeSel := DataTypeSelector(0xfe)
return decodeWithSelector(r, iface, typeSel)
}
func decodeWithSelector(r io.Reader, iface interface{}, typeSel DataTypeSelector) error {
val := reflect.ValueOf(iface)
if val.Kind() != reflect.Ptr {
return fmt.Errorf("need ptr argument: %T", iface)
}
val = val.Elem()
t := val.Type()
for i := 0; i < t.NumField(); i++ {
if err := decodeField(r, val.Field(i), typeSel); err != nil {
return err
}
if val.Field(i).Type().Name() == "DataTypeSelector" {
typeSel = val.Field(i).Interface().(DataTypeSelector)
}
}
return nil
}
// Encode MTP data stream into data structure.
func Encode(w io.Writer, iface interface{}) error {
encoder, ok := iface.(Encoder)
if ok {
return encoder.Encode(w)
}
val := reflect.ValueOf(iface)
if val.Kind() != reflect.Ptr {
msg := fmt.Sprintf("need ptr argument: %T", iface)
return fmt.Errorf(msg)
//panic("need ptr argument: %T")
}
val = val.Elem()
t := val.Type()
for i := 0; i < t.NumField(); i++ {
if err := encodeField(w, val.Field(i)); err != nil {
return err
}
}
return nil
}
// Instantiates an object of wanted type as addressable value.
func InstantiateType(t DataTypeSelector) reflect.Value {
var val interface{}
switch t {
case DTC_INT8:
v := int8(0)
val = &v
case DTC_UINT8:
v := int8(0)
val = &v
case DTC_INT16:
v := int16(0)
val = &v
case DTC_UINT16:
v := uint16(0)
val = &v
case DTC_INT32:
v := int32(0)
val = &v
case DTC_UINT32:
v := uint32(0)
val = &v
case DTC_INT64:
v := int64(0)
val = &v
case DTC_UINT64:
v := uint64(0)
val = &v
case DTC_INT128:
v := [16]byte{}
val = &v
case DTC_UINT128:
v := [16]byte{}
val = &v
case DTC_STR:
s := ""
val = &s
default:
panic(fmt.Sprintf("type not known 0x%x", t))
}
return reflect.ValueOf(val).Elem()
}
func decodePropDescForm(r io.Reader, selector DataTypeSelector, formFlag uint8) (DataDependentType, error) {
if formFlag == DPFF_Range {
f := PropDescRangeForm{}
err := decodeWithSelector(r, reflect.ValueOf(&f).Interface(),
selector)
return &f, err
} else if formFlag == DPFF_Enumeration {
f := PropDescEnumForm{}
err := decodeWithSelector(r, reflect.ValueOf(&f).Interface(),
selector)
return &f, err
}
return nil, nil
}
func (pd *ObjectPropDesc) Decode(r io.Reader) error {
if err := Decode(r, &pd.ObjectPropDescFixed); err != nil {
return err
}
form, err := decodePropDescForm(r, pd.DataType, pd.FormFlag)
pd.Form = form
return err
}
func (pd *DevicePropDesc) Decode(r io.Reader) error {
if err := Decode(r, &pd.DevicePropDescFixed); err != nil {
return err
}
form, err := decodePropDescForm(r, pd.DataType, pd.FormFlag)
pd.Form = form
return err
}
func (pd *DevicePropDesc) Encode(w io.Writer) error {
if err := Encode(w, &pd.DevicePropDescFixed); err != nil {
return err
}
return Encode(w, pd.Form)
}
func (pd *ObjectPropDesc) Encode(w io.Writer) error {
if err := Encode(w, &pd.ObjectPropDescFixed); err != nil {
return err
}
return Encode(w, pd.Form)
}
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