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decoder.go
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decoder.go
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package wbxml
import (
"fmt"
"io"
"reflect"
"strconv"
)
// Unmarshaler is an interface implemented by a type that wish to control how it is
// decoded from WBXML.
//
// Mostly used when a type is not supported by default by Decoder.DecodeElement.
type Unmarshaler interface {
UnmarshalWBXML(d *Decoder, st *StartElement) error
}
// Decoder decodes a WBXML stream.
type Decoder struct {
r io.Reader
tagPage byte
tags CodeSpace
attrPage byte
attrs CodeSpace
offset int
tokChan chan Token
err error
Header Header
}
// NewDecoder instantiate a Decoder, with r as a stream of WBXML.
func NewDecoder(r io.Reader, tags CodeSpace, attrs CodeSpace) *Decoder {
d := &Decoder{
r: r,
tags: tags,
attrs: attrs,
tokChan: make(chan Token),
}
go d.run()
return d
}
// GetString returns the string of the string table starting at byte i and ending a the first
// meet NULL terminator. It returns nil and error if i bigger than the string table, or no NULL
// terminator is found.
func (d *Decoder) GetString(i uint32) ([]byte, error) {
if i >= uint32(len(d.Header.StringTable)) {
return nil, fmt.Errorf("%d is not a valid string reference (max %d)", i, len(d.Header.StringTable))
}
for end, b := range d.Header.StringTable[i:] {
if b == 0 {
return d.Header.StringTable[i : i+uint32(end)], nil
}
}
return nil, fmt.Errorf("StringTable: no NULL terminator found")
}
// Token returns the next token in the WBXML stream, or an error.
// At end it returns nil and io.EOF.
// It is mostly used by types implementing Unmarshaler.
func (d *Decoder) Token() (Token, error) {
tok := <-d.tokChan
if tok == nil {
return tok, d.err
}
return tok, nil
}
// Decode decodes a WBXML document to v.
func (d *Decoder) Decode(v interface{}) error {
return d.DecodeElement(v, nil)
}
// DecodeElement decodes the root element and its child to v.
// It is mostly used by types implementing Unmarshaler that wish to
// delegate parts of the decoding.
func (d *Decoder) DecodeElement(v interface{}, start *StartElement) error {
if start == nil {
tok, err := d.Token()
if err != nil {
return err
}
if st, ok := tok.(StartElement); ok {
start = &st
} else {
return fmt.Errorf("expected a StartElement, got %t", tok)
}
}
val := reflect.ValueOf(v)
if val.Kind() == reflect.Interface && !val.IsNil() {
val = val.Elem()
}
if val.Kind() == reflect.Ptr {
if val.IsNil() {
val.Set(reflect.New(val.Type().Elem()))
}
if un, ok := val.Interface().(Unmarshaler); ok {
return un.UnmarshalWBXML(d, start)
}
val = val.Elem()
}
switch t := val.Type(); val.Kind() {
case reflect.Struct:
for {
tok, err := d.Token()
if err != nil {
return err
}
if end, ok := tok.(EndElement); ok {
if end.Name == start.Name {
return nil
}
return fmt.Errorf("expected end element %s, got %s", start.Name, end.Name)
}
if st, ok := tok.(StartElement); ok {
if _, ok := t.FieldByName(st.Name); ok {
fld := val.FieldByName(st.Name)
if fld.Kind() == reflect.Ptr && fld.IsNil() {
fld.Set(reflect.New(fld.Type().Elem()))
}
if fld.Kind() != reflect.Ptr && fld.CanAddr() {
fld = fld.Addr()
}
if fld.CanInterface() {
err := d.DecodeElement(fld.Interface(), &st)
if err != nil {
return err
}
} else {
return fmt.Errorf("tag %s: type %s can't be used as interface{}", st.Name, t.Name())
}
} else {
// struct has no field named st.Name, find its end tag and iterate.
for {
tok, err := d.Token()
if err != nil {
return err
}
if end, ok := tok.(EndElement); ok && end.Name == st.Name {
break
}
}
}
}
}
case reflect.String:
tok, err := d.Token()
if err != nil {
return err
}
if cdata, ok := tok.(CharData); ok {
val.SetString(string(cdata))
return d.expectedEnd(start)
}
if opaque, ok := tok.(Opaque); ok {
val.SetString(string(opaque))
return d.expectedEnd(start)
}
return fmt.Errorf("string expected a CharData, got %t", tok)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
tok, err := d.Token()
if err != nil {
return err
}
switch itok := tok.(type) {
case Entity:
val.SetUint(uint64(itok))
case CharData:
i, err := strconv.ParseUint(string(itok), 10, 8)
if err != nil {
return fmt.Errorf("field %s: %s", start.Name, err)
}
val.SetUint(i)
default:
return fmt.Errorf("expected a number, got %T", tok)
}
return d.expectedEnd(start)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
tok, err := d.Token()
if err != nil {
return err
}
switch itok := tok.(type) {
case Entity:
val.SetInt(int64(itok))
case CharData:
i, err := strconv.ParseInt(string(itok), 10, 8)
if err != nil {
return fmt.Errorf("field %s: %s", start.Name, err)
}
val.SetInt(i)
default:
return fmt.Errorf("expected a number, got %T", tok)
}
return d.expectedEnd(start)
case reflect.Bool:
val.SetBool(true)
return d.expectedEnd(start)
case reflect.Slice:
if t.Elem().Kind() == reflect.Uint8 {
tok, err := d.Token()
if err != nil {
return err
}
if cdata, ok := tok.(CharData); ok {
val.Set(reflect.AppendSlice(val, reflect.ValueOf(cdata)))
return d.expectedEnd(start)
}
if opaque, ok := tok.(Opaque); ok {
val.Set(reflect.AppendSlice(val, reflect.ValueOf(opaque)))
return d.expectedEnd(start)
}
if end, ok := tok.(EndElement); ok && end.Name == start.Name {
return nil
}
return fmt.Errorf("[]byte expected a CharData, got %t", tok)
}
// Append element to slice
n := val.Len()
val.Set(reflect.Append(val, reflect.Zero(t.Elem())))
// Decode element, remove it if failed
if err := d.DecodeElement(val.Index(n).Addr().Interface(), start); err != nil {
val.SetLen(n)
return err
}
return nil
default:
return fmt.Errorf("%s not implemented", t.Kind())
}
}
func (d *Decoder) expectedEnd(start *StartElement) error {
tok, err := d.Token()
if err != nil {
return err
}
if end, ok := tok.(EndElement); !ok || end.Name != start.Name {
return fmt.Errorf("expected end element %s, got %+v", start.Name, tok)
}
return nil
}
func (d *Decoder) tagName(code byte) string {
name, err := d.tags.Name(d.tagPage, code)
if err != nil {
d.panicErr(err)
}
return name
}
func (d *Decoder) attrName(code byte) string {
name, err := d.attrs.Name(d.attrPage, code)
if err != nil {
d.panicErr(err)
}
return name
}
func (d *Decoder) run() {
defer func() {
if r := recover(); r != nil {
if err, ok := r.(error); ok {
d.err = err
close(d.tokChan)
return
}
panic(r)
}
}()
h, err := d.readHeader()
d.panicErr(err)
d.Header = h
d.body()
close(d.tokChan)
}
// readHeader reads the wbxml header.
func (d *Decoder) readHeader() (Header, error) {
var h Header
var err error
h.Version, err = readByte(d)
if err != nil {
return h, err
}
h.PublicID, err = mbUint32(d)
if err != nil {
return h, err
}
if h.PublicID == 0 {
h.PublicID, err = mbUint32(d)
}
h.Charset, err = mbUint32(d)
if err != nil {
return h, err
}
length, err := mbUint32(d)
if err != nil {
return h, err
}
buf := make([]byte, length)
n, err := d.r.Read(buf)
if err != nil {
return h, err
}
d.offset += n
h.StringTable = buf
return h, nil
}
func (d *Decoder) body() {
var b byte
var err error
for {
b, err = readByte(d)
d.panicErr(err)
if b != gloPi {
break
}
d.piStar()
}
d.element(b)
for {
b, err = readByte(d)
d.panicErr(err)
if b != gloPi {
break
}
d.piStar()
}
}
func (d *Decoder) piStar() {
}
func (d *Decoder) element(b byte) {
switch b {
case gloSwitchPage:
index, err := readByte(d)
d.panicErr(err)
d.tagPage = index
case gloLiteral, gloLiteralA, gloLiteralC, gloLiteralAC:
panic(fmt.Errorf("literal tag not implemented"))
default:
tag := Tag(b)
tagName := d.tagName(tag.ID())
tok := StartElement{Name: tagName}
if tag.Attr() {
d.attributes(&tok)
}
tok.Content = tag.Content()
tok.Offset = d.offset - 1
d.tokChan <- tok
if tag.Content() {
d.content()
}
d.tokChan <- EndElement{Name: tagName, Offset: d.offset}
}
}
func (d *Decoder) attributes(elt *StartElement) {
b, err := readByte(d)
d.panicErr(err)
for {
switch b {
case gloSwitchPage:
index, err := readByte(d)
d.panicErr(err)
d.attrPage = index
case gloLiteral:
var attr Attr
index, err := mbUint32(d)
d.panicErr(err)
name, err := d.GetString(index)
d.panicErr(err)
attr.Name = string(name)
attr.Value, b = d.readAttrValue()
elt.Attr = append(elt.Attr, attr)
case gloEnd:
return
default:
if b >= 128 {
panic(fmt.Errorf("unexpected attribute value"))
}
var attr Attr
attr.Name = d.attrName(b)
attr.Value, b = d.readAttrValue()
elt.Attr = append(elt.Attr, attr)
}
}
}
func (d *Decoder) readAttrValue() (string, byte) {
var cdata CharData
for {
b, err := readByte(d)
d.panicErr(err)
switch b {
case gloSwitchPage:
index, err := readByte(d)
d.panicErr(err)
d.attrPage = index
case gloStrI, gloStrT, gloEntity:
d.charData(&cdata, b)
case gloExt0, gloExt1, gloExt2,
gloExtI0, gloExtI1, gloExtI2,
gloExtT0, gloExtT1, gloExtT2:
panic(fmt.Errorf("extension token unimplemented (token %d)", b))
case gloEnd:
return string(cdata), b
default:
if b < 128 {
return string(cdata), b
//panic(fmt.Errorf("unexpected attribute tag name %d", b))
}
cdata = append(cdata, []byte(d.attrName(b))...)
}
}
}
func (d *Decoder) content() {
// content() accumulate adjacent CharData in a unique instance until END or ELEMENT is
// encountered
var cdata CharData
for {
b, err := readByte(d)
d.panicErr(err)
switch b {
case gloStrI, gloStrT, gloEntity:
d.charData(&cdata, b)
case gloOpaque:
d.sendCharData(&cdata)
length, err := mbUint32(d)
d.panicErr(err)
data, err := readSlice(d, length)
d.panicErr(err)
d.tokChan <- Opaque(data)
case gloExt0, gloExt1, gloExt2,
gloExtI0, gloExtI1, gloExtI2,
gloExtT0, gloExtT1, gloExtT2:
panic(fmt.Errorf("extension token unimplemented (token %d)", b))
case gloEnd:
d.sendCharData(&cdata)
return
default:
d.sendCharData(&cdata)
d.element(b)
}
}
}
func (d *Decoder) sendCharData(cdata *CharData) {
if *cdata != nil {
d.tokChan <- *cdata
*cdata = nil
}
}
func (d *Decoder) charData(cdata *CharData, b byte) {
if cdata == nil {
*cdata = make([]byte, 0)
}
switch b {
case gloStrI:
str, err := readString(d)
d.panicErr(err)
*cdata = append(*cdata, str...)
case gloStrT:
index, err := mbUint32(d)
d.panicErr(err)
str, err := d.GetString(index)
d.panicErr(err)
*cdata = append(*cdata, str...)
case gloEntity:
entcode, err := mbUint32(d)
d.panicErr(err)
entity := Entity(entcode)
if len(*cdata) > 0 {
*cdata = append(*cdata, entity.UTF8()...)
} else {
d.tokChan <- entity
}
default:
d.panicErr(fmt.Errorf("Unknown char data tag %d", b))
}
}