311 lines
6.9 KiB
Go
311 lines
6.9 KiB
Go
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package syntax
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import (
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"bytes"
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"fmt"
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"reflect"
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"runtime"
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)
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func Unmarshal(data []byte, v interface{}) (int, error) {
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// Check for well-formedness.
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// Avoids filling out half a data structure
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// before discovering a JSON syntax error.
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d := decodeState{}
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d.Write(data)
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return d.unmarshal(v)
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}
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// Unmarshaler is the interface implemented by types that can
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// unmarshal a TLS description of themselves. Note that unlike the
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// JSON unmarshaler interface, it is not known a priori how much of
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// the input data will be consumed. So the Unmarshaler must state
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// how much of the input data it consumed.
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type Unmarshaler interface {
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UnmarshalTLS([]byte) (int, error)
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}
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// These are the options that can be specified in the struct tag. Right now,
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// all of them apply to variable-length vectors and nothing else
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type decOpts struct {
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head uint // length of length in bytes
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min uint // minimum size in bytes
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max uint // maximum size in bytes
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varint bool // whether to decode as a varint
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}
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type decodeState struct {
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bytes.Buffer
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}
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func (d *decodeState) unmarshal(v interface{}) (read int, err error) {
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defer func() {
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if r := recover(); r != nil {
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if _, ok := r.(runtime.Error); ok {
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panic(r)
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}
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if s, ok := r.(string); ok {
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panic(s)
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}
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err = r.(error)
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}
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}()
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rv := reflect.ValueOf(v)
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if rv.Kind() != reflect.Ptr || rv.IsNil() {
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return 0, fmt.Errorf("Invalid unmarshal target (non-pointer or nil)")
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}
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read = d.value(rv)
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return read, nil
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}
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func (e *decodeState) value(v reflect.Value) int {
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return valueDecoder(v)(e, v, decOpts{})
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}
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type decoderFunc func(e *decodeState, v reflect.Value, opts decOpts) int
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func valueDecoder(v reflect.Value) decoderFunc {
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return typeDecoder(v.Type().Elem())
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}
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func typeDecoder(t reflect.Type) decoderFunc {
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// Note: Omits the caching / wait-group things that encoding/json uses
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return newTypeDecoder(t)
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}
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var (
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unmarshalerType = reflect.TypeOf(new(Unmarshaler)).Elem()
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)
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func newTypeDecoder(t reflect.Type) decoderFunc {
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if t.Kind() != reflect.Ptr && reflect.PtrTo(t).Implements(unmarshalerType) {
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return unmarshalerDecoder
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}
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switch t.Kind() {
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case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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return uintDecoder
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case reflect.Array:
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return newArrayDecoder(t)
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case reflect.Slice:
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return newSliceDecoder(t)
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case reflect.Struct:
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return newStructDecoder(t)
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case reflect.Ptr:
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return newPointerDecoder(t)
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default:
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panic(fmt.Errorf("Unsupported type (%s)", t))
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}
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}
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///// Specific decoders below
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func unmarshalerDecoder(d *decodeState, v reflect.Value, opts decOpts) int {
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um, ok := v.Interface().(Unmarshaler)
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if !ok {
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panic(fmt.Errorf("Non-Unmarshaler passed to unmarshalerEncoder"))
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}
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read, err := um.UnmarshalTLS(d.Bytes())
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if err != nil {
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panic(err)
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}
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if read > d.Len() {
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panic(fmt.Errorf("Invalid return value from UnmarshalTLS"))
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}
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d.Next(read)
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return read
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}
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//////////
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func uintDecoder(d *decodeState, v reflect.Value, opts decOpts) int {
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if opts.varint {
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return varintDecoder(d, v, opts)
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}
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uintLen := int(v.Elem().Type().Size())
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buf := d.Next(uintLen)
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if len(buf) != uintLen {
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panic(fmt.Errorf("Insufficient data to read uint"))
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}
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return setUintFromBuffer(v, buf)
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}
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func varintDecoder(d *decodeState, v reflect.Value, opts decOpts) int {
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// Read the first octet and decide the size of the presented varint
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first := d.Next(1)
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if len(first) != 1 {
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panic(fmt.Errorf("Insufficient data to read varint length"))
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}
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uintLen := int(v.Elem().Type().Size())
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twoBits := uint(first[0] >> 6)
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varintLen := 1 << twoBits
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if uintLen < varintLen {
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panic(fmt.Errorf("Uint too small to fit varint: %d < %d"))
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}
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rest := d.Next(varintLen - 1)
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if len(rest) != varintLen-1 {
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panic(fmt.Errorf("Insufficient data to read varint"))
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}
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buf := append(first, rest...)
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buf[0] &= 0x3f
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return setUintFromBuffer(v, buf)
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}
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func setUintFromBuffer(v reflect.Value, buf []byte) int {
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val := uint64(0)
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for _, b := range buf {
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val = (val << 8) + uint64(b)
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}
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v.Elem().SetUint(val)
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return len(buf)
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}
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//////////
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type arrayDecoder struct {
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elemDec decoderFunc
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}
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func (ad *arrayDecoder) decode(d *decodeState, v reflect.Value, opts decOpts) int {
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n := v.Elem().Type().Len()
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read := 0
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for i := 0; i < n; i += 1 {
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read += ad.elemDec(d, v.Elem().Index(i).Addr(), opts)
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}
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return read
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}
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func newArrayDecoder(t reflect.Type) decoderFunc {
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dec := &arrayDecoder{typeDecoder(t.Elem())}
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return dec.decode
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}
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//////////
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type sliceDecoder struct {
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elementType reflect.Type
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elementDec decoderFunc
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}
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func (sd *sliceDecoder) decode(d *decodeState, v reflect.Value, opts decOpts) int {
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if opts.head == 0 {
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panic(fmt.Errorf("Cannot decode a slice without a header length"))
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}
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lengthBytes := d.Next(int(opts.head))
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if len(lengthBytes) != int(opts.head) {
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panic(fmt.Errorf("Not enough data to read header"))
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}
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length := uint(0)
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for _, b := range lengthBytes {
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length = (length << 8) + uint(b)
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}
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if opts.max > 0 && length > opts.max {
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panic(fmt.Errorf("Length of vector exceeds declared max"))
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}
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if length < opts.min {
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panic(fmt.Errorf("Length of vector below declared min"))
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}
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data := d.Next(int(length))
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if len(data) != int(length) {
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panic(fmt.Errorf("Available data less than declared length [%d < %d]", len(data), length))
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}
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elemBuf := &decodeState{}
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elemBuf.Write(data)
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elems := []reflect.Value{}
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read := int(opts.head)
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for elemBuf.Len() > 0 {
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elem := reflect.New(sd.elementType)
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read += sd.elementDec(elemBuf, elem, opts)
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elems = append(elems, elem)
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}
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v.Elem().Set(reflect.MakeSlice(v.Elem().Type(), len(elems), len(elems)))
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for i := 0; i < len(elems); i += 1 {
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v.Elem().Index(i).Set(elems[i].Elem())
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}
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return read
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}
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func newSliceDecoder(t reflect.Type) decoderFunc {
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dec := &sliceDecoder{
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elementType: t.Elem(),
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elementDec: typeDecoder(t.Elem()),
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}
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return dec.decode
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}
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//////////
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type structDecoder struct {
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fieldOpts []decOpts
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fieldDecs []decoderFunc
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}
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func (sd *structDecoder) decode(d *decodeState, v reflect.Value, opts decOpts) int {
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read := 0
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for i := range sd.fieldDecs {
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read += sd.fieldDecs[i](d, v.Elem().Field(i).Addr(), sd.fieldOpts[i])
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}
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return read
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}
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func newStructDecoder(t reflect.Type) decoderFunc {
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n := t.NumField()
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sd := structDecoder{
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fieldOpts: make([]decOpts, n),
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fieldDecs: make([]decoderFunc, n),
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}
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for i := 0; i < n; i += 1 {
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f := t.Field(i)
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tag := f.Tag.Get("tls")
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tagOpts := parseTag(tag)
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sd.fieldOpts[i] = decOpts{
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head: tagOpts["head"],
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max: tagOpts["max"],
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min: tagOpts["min"],
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varint: tagOpts[varintOption] > 0,
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}
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sd.fieldDecs[i] = typeDecoder(f.Type)
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}
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return sd.decode
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}
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//////////
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type pointerDecoder struct {
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base decoderFunc
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}
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func (pd *pointerDecoder) decode(d *decodeState, v reflect.Value, opts decOpts) int {
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v.Elem().Set(reflect.New(v.Elem().Type().Elem()))
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return pd.base(d, v.Elem(), opts)
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}
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func newPointerDecoder(t reflect.Type) decoderFunc {
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baseDecoder := typeDecoder(t.Elem())
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pd := pointerDecoder{base: baseDecoder}
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return pd.decode
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}
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