package rlp
import (
"bufio"
"encoding/binary"
"errors"
"fmt"
"io"
"math/big"
"reflect"
)
var (
errNoPointer = errors.New("rlp: interface given to Decode must be a pointer")
errDecodeIntoNil = errors.New("rlp: pointer given to Decode must not be nil")
)
// Decoder is implemented by types that require custom RLP
// decoding rules or need to decode into private fields.
//
// The DecodeRLP method should read one value from the given
// Stream. It is not forbidden to read less or more, but it might
// be confusing.
type Decoder interface {
DecodeRLP(*Stream) error
}
// Decode parses RLP-encoded data from r and stores the result in the
// value pointed to by val. Val must be a non-nil pointer. If r does
// not implement ByteReader, Decode will do its own buffering.
//
// Decode uses the following type-dependent decoding rules:
//
// If the type implements the Decoder interface, decode calls
// DecodeRLP.
//
// To decode into a pointer, Decode will set the pointer to nil if the
// input has size zero or the input is a single byte with value zero.
// If the input has nonzero size, Decode will allocate a new value of
// the type being pointed to.
//
// To decode into a struct, Decode expects the input to be an RLP
// list. The decoded elements of the list are assigned to each public
// field in the order given by the struct's definition. If the input
// list has too few elements, no error is returned and the remaining
// fields will have the zero value.
// Recursive struct types are supported.
//
// To decode into a slice, the input must be a list and the resulting
// slice will contain the input elements in order.
// As a special case, if the slice has a byte-size element type, the input
// can also be an RLP string.
//
// To decode into a Go string, the input must be an RLP string. The
// bytes are taken as-is and will not necessarily be valid UTF-8.
//
// To decode into an unsigned integer type, the input must also be an RLP
// string. The bytes are interpreted as a big endian representation of
// the integer. If the RLP string is larger than the bit size of the
// type, Decode will return an error. Decode also supports *big.Int.
// There is no size limit for big integers.
//
// To decode into an interface value, Decode stores one of these
// in the value:
//
// []interface{}, for RLP lists
// []byte, for RLP strings
//
// Non-empty interface types are not supported, nor are booleans,
// signed integers, floating point numbers, maps, channels and
// functions.
func Decode(r io.Reader, val interface{}) error {
return NewStream(r).Decode(val)
}
type decodeError struct {
msg string
typ reflect.Type
}
func (err decodeError) Error() string {
return fmt.Sprintf("rlp: %s for %v", err.msg, err.typ)
}
func wrapStreamError(err error, typ reflect.Type) error {
switch err {
case ErrExpectedList:
return decodeError{"expected input list", typ}
case ErrExpectedString:
return decodeError{"expected input string or byte", typ}
case errUintOverflow:
return decodeError{"input string too long", typ}
case errNotAtEOL:
return decodeError{"input list has too many elements", typ}
}
return err
}
var (
decoderInterface = reflect.TypeOf(new(Decoder)).Elem()
bigInt = reflect.TypeOf(big.Int{})
)
func makeDecoder(typ reflect.Type) (dec decoder, err error) {
kind := typ.Kind()
switch {
case typ.Implements(decoderInterface):
return decodeDecoder, nil
case kind != reflect.Ptr && reflect.PtrTo(typ).Implements(decoderInterface):
return decodeDecoderNoPtr, nil
case typ.AssignableTo(reflect.PtrTo(bigInt)):
return decodeBigInt, nil
case typ.AssignableTo(bigInt):
return decodeBigIntNoPtr, nil
case isUint(kind):
return decodeUint, nil
case kind == reflect.String:
return decodeString, nil
case kind == reflect.Slice || kind == reflect.Array:
return makeListDecoder(typ)
case kind == reflect.Struct:
return makeStructDecoder(typ)
case kind == reflect.Ptr:
return makePtrDecoder(typ)
case kind == reflect.Interface && typ.NumMethod() == 0:
return decodeInterface, nil
default:
return nil, fmt.Errorf("rlp: type %v is not RLP-serializable", typ)
}
}
func decodeUint(s *Stream, val reflect.Value) error {
typ := val.Type()
num, err := s.uint(typ.Bits())
if err != nil {
return wrapStreamError(err, val.Type())
}
val.SetUint(num)
return nil
}
func decodeString(s *Stream, val reflect.Value) error {
b, err := s.Bytes()
if err != nil {
return wrapStreamError(err, val.Type())
}
val.SetString(string(b))
return nil
}
func decodeBigIntNoPtr(s *Stream, val reflect.Value) error {
return decodeBigInt(s, val.Addr())
}
func decodeBigInt(s *Stream, val reflect.Value) error {
b, err := s.Bytes()
if err != nil {
return wrapStreamError(err, val.Type())
}
i := val.Interface().(*big.Int)
if i == nil {
i = new(big.Int)
val.Set(reflect.ValueOf(i))
}
i.SetBytes(b)
return nil
}
func makeListDecoder(typ reflect.Type) (decoder, error) {
etype := typ.Elem()
if etype.Kind() == reflect.Uint8 && !reflect.PtrTo(etype).Implements(decoderInterface) {
if typ.Kind() == reflect.Array {
return decodeByteArray, nil
} else {
return decodeByteSlice, nil
}
}
etypeinfo, err := cachedTypeInfo1(etype)
if err != nil {
return nil, err
}
if typ.Kind() == reflect.Array {
return func(s *Stream, val reflect.Value) error {
return decodeListArray(s, val, etypeinfo.decoder)
}, nil
}
return func(s *Stream, val reflect.Value) error {
return decodeListSlice(s, val, etypeinfo.decoder)
}, nil
}
func decodeListSlice(s *Stream, val reflect.Value, elemdec decoder) error {
size, err := s.List()
if err != nil {
return wrapStreamError(err, val.Type())
}
if size == 0 {
val.Set(reflect.MakeSlice(val.Type(), 0, 0))
return s.ListEnd()
}
i := 0
for ; ; i++ {
// grow slice if necessary
if i >= val.Cap() {
newcap := val.Cap() + val.Cap()/2
if newcap < 4 {
newcap = 4
}
newv := reflect.MakeSlice(val.Type(), val.Len(), newcap)
reflect.Copy(newv, val)
val.Set(newv)
}
if i >= val.Len() {
val.SetLen(i + 1)
}
// decode into element
if err := elemdec(s, val.Index(i)); err == EOL {
break
} else if err != nil {
return err
}
}
if i < val.Len() {
val.SetLen(i)
}
return s.ListEnd()
}
func decodeListArray(s *Stream, val reflect.Value, elemdec decoder) error {
size, err := s.List()
if err != nil {
return err
}
if size == 0 {
zero(val, 0)
return s.ListEnd()
}
// The approach here is stolen from package json, although we differ
// in the semantics for arrays. package json discards remaining
// elements that would not fit into the array. We generate an error in
// this case because we'd be losing information.
vlen := val.Len()
i := 0
for ; i < vlen; i++ {
if err := elemdec(s, val.Index(i)); err == EOL {
break
} else if err != nil {
return err
}
}
if i < vlen {
zero(val, i)
}
return wrapStreamError(s.ListEnd(), val.Type())
}
func decodeByteSlice(s *Stream, val reflect.Value) error {
kind, _, err := s.Kind()
if err != nil {
return err
}
if kind == List {
return decodeListSlice(s, val, decodeUint)
}
b, err := s.Bytes()
if err == nil {
val.SetBytes(b)
}
return err
}
func decodeByteArray(s *Stream, val reflect.Value) error {
kind, size, err := s.Kind()
if err != nil {
return err
}
switch kind {
case Byte:
if val.Len() == 0 {
return decodeError{"input string too long", val.Type()}
}
bv, _ := s.Uint()
val.Index(0).SetUint(bv)
zero(val, 1)
case String:
if uint64(val.Len()) < size {
return decodeError{"input string too long", val.Type()}
}
slice := val.Slice(0, int(size)).Interface().([]byte)
if err := s.readFull(slice); err != nil {
return err
}
zero(val, int(size))
case List:
return decodeListArray(s, val, decodeUint)
}
return nil
}
func zero(val reflect.Value, start int) {
z := reflect.Zero(val.Type().Elem())
end := val.Len()
for i := start; i < end; i++ {
val.Index(i).Set(z)
}
}
type field struct {
index int
info *typeinfo
}
func makeStructDecoder(typ reflect.Type) (decoder, error) {
var fields []field
for i := 0; i < typ.NumField(); i++ {
if f := typ.Field(i); f.PkgPath == "" { // exported
info, err := cachedTypeInfo1(f.Type)
if err != nil {
return nil, err
}
fields = append(fields, field{i, info})
}
}
dec := func(s *Stream, val reflect.Value) (err error) {
if _, err = s.List(); err != nil {
return wrapStreamError(err, typ)
}
for _, f := range fields {
err = f.info.decoder(s, val.Field(f.index))
if err == EOL {
// too few elements. leave the rest at their zero value.
break
} else if err != nil {
return err
}
}
return wrapStreamError(s.ListEnd(), typ)
}
return dec, nil
}
func makePtrDecoder(typ reflect.Type) (decoder, error) {
etype := typ.Elem()
etypeinfo, err := cachedTypeInfo1(etype)
if err != nil {
return nil, err
}
dec := func(s *Stream, val reflect.Value) (err error) {
_, size, err := s.Kind()
if err != nil || size == 0 && s.byteval == 0 {
val.Set(reflect.Zero(typ)) // set to nil
return err
}
newval := val
if val.IsNil() {
newval = reflect.New(etype)
}
if err = etypeinfo.decoder(s, newval.Elem()); err == nil {
val.Set(newval)
}
return err
}
return dec, nil
}
var ifsliceType = reflect.TypeOf([]interface{}{})
func decodeInterface(s *Stream, val reflect.Value) error {
kind, _, err := s.Kind()
if err != nil {
return err
}
if kind == List {
slice := reflect.New(ifsliceType).Elem()
if err := decodeListSlice(s, slice, decodeInterface); err != nil {
return err
}
val.Set(slice)
} else {
b, err := s.Bytes()
if err != nil {
return err
}
val.Set(reflect.ValueOf(b))
}
return nil
}
// This decoder is used for non-pointer values of types
// that implement the Decoder interface using a pointer receiver.
func decodeDecoderNoPtr(s *Stream, val reflect.Value) error {
return val.Addr().Interface().(Decoder).DecodeRLP(s)
}
func decodeDecoder(s *Stream, val reflect.Value) error {
// Decoder instances are not handled using the pointer rule if the type
// implements Decoder with pointer receiver (i.e. always)
// because it might handle empty values specially.
// We need to allocate one here in this case, like makePtrDecoder does.
if val.Kind() == reflect.Ptr && val.IsNil() {
val.Set(reflect.New(val.Type().Elem()))
}
return val.Interface().(Decoder).DecodeRLP(s)
}
// Kind represents the kind of value contained in an RLP stream.
type Kind int
const (
Byte Kind = iota
String
List
)
func (k Kind) String() string {
switch k {
case Byte:
return "Byte"
case String:
return "String"
case List:
return "List"
default:
return fmt.Sprintf("Unknown(%d)", k)
}
}
var (
// EOL is returned when the end of the current list
// has been reached during streaming.
EOL = errors.New("rlp: end of list")
// Other errors
ErrExpectedString = errors.New("rlp: expected String or Byte")
ErrExpectedList = errors.New("rlp: expected List")
ErrElemTooLarge = errors.New("rlp: element is larger than containing list")
// internal errors
errNotInList = errors.New("rlp: call of ListEnd outside of any list")
errNotAtEOL = errors.New("rlp: call of ListEnd not positioned at EOL")
)
// ByteReader must be implemented by any input reader for a Stream. It
// is implemented by e.g. bufio.Reader and bytes.Reader.
type ByteReader interface {
io.Reader
io.ByteReader
}
// Stream can be used for piecemeal decoding of an input stream. This
// is useful if the input is very large or if the decoding rules for a
// type depend on the input structure. Stream does not keep an
// internal buffer. After decoding a value, the input reader will be
// positioned just before the type information for the next value.
//
// When decoding a list and the input position reaches the declared
// length of the list, all operations will return error EOL.
// The end of the list must be acknowledged using ListEnd to continue
// reading the enclosing list.
//
// Stream is not safe for concurrent use.
type Stream struct {
r ByteReader
uintbuf []byte
kind Kind // kind of value ahead
size uint64 // size of value ahead
byteval byte // value of single byte in type tag
stack []listpos
}
type listpos struct{ pos, size uint64 }
// NewStream creates a new stream reading from r.
// If r does not implement ByteReader, the Stream will
// introduce its own buffering.
func NewStream(r io.Reader) *Stream {
s := new(Stream)
s.Reset(r)
return s
}
// NewListStream creates a new stream that pretends to be positioned
// at an encoded list of the given length.
func NewListStream(r io.Reader, len uint64) *Stream {
s := new(Stream)
s.Reset(r)
s.kind = List
s.size = len
return s
}
// Bytes reads an RLP string and returns its contents as a byte slice.
// If the input does not contain an RLP string, the returned
// error will be ErrExpectedString.
func (s *Stream) Bytes() ([]byte, error) {
kind, size, err := s.Kind()
if err != nil {
return nil, err
}
switch kind {
case Byte:
s.kind = -1 // rearm Kind
return []byte{s.byteval}, nil
case String:
b := make([]byte, size)
if err = s.readFull(b); err != nil {
return nil, err
}
return b, nil
default:
return nil, ErrExpectedString
}
}
var errUintOverflow = errors.New("rlp: uint overflow")
// Uint reads an RLP string of up to 8 bytes and returns its contents
// as an unsigned integer. If the input does not contain an RLP string, the
// returned error will be ErrExpectedString.
func (s *Stream) Uint() (uint64, error) {
return s.uint(64)
}
func (s *Stream) uint(maxbits int) (uint64, error) {
kind, size, err := s.Kind()
if err != nil {
return 0, err
}
switch kind {
case Byte:
s.kind = -1 // rearm Kind
return uint64(s.byteval), nil
case String:
if size > uint64(maxbits/8) {
return 0, errUintOverflow
}
return s.readUint(byte(size))
default:
return 0, ErrExpectedString
}
}
// List starts decoding an RLP list. If the input does not contain a
// list, the returned error will be ErrExpectedList. When the list's
// end has been reached, any Stream operation will return EOL.
func (s *Stream) List() (size uint64, err error) {
kind, size, err := s.Kind()
if err != nil {
return 0, err
}
if kind != List {
return 0, ErrExpectedList
}
s.stack = append(s.stack, listpos{0, size})
s.kind = -1
s.size = 0
return size, nil
}
// ListEnd returns to the enclosing list.
// The input reader must be positioned at the end of a list.
func (s *Stream) ListEnd() error {
if len(s.stack) == 0 {
return errNotInList
}
tos := s.stack[len(s.stack)-1]
if tos.pos != tos.size {
return errNotAtEOL
}
s.stack = s.stack[:len(s.stack)-1] // pop
if len(s.stack) > 0 {
s.stack[len(s.stack)-1].pos += tos.size
}
s.kind = -1
s.size = 0
return nil
}
// Decode decodes a value and stores the result in the value pointed
// to by val. Please see the documentation for the Decode function
// to learn about the decoding rules.
func (s *Stream) Decode(val interface{}) error {
if val == nil {
return errDecodeIntoNil
}
rval := reflect.ValueOf(val)
rtyp := rval.Type()
if rtyp.Kind() != reflect.Ptr {
return errNoPointer
}
if rval.IsNil() {
return errDecodeIntoNil
}
info, err := cachedTypeInfo(rtyp.Elem())
if err != nil {
return err
}
return info.decoder(s, rval.Elem())
}
// Reset discards any information about the current decoding context
// and starts reading from r. If r does not also implement ByteReader,
// Stream will do its own buffering.
func (s *Stream) Reset(r io.Reader) {
bufr, ok := r.(ByteReader)
if !ok {
bufr = bufio.NewReader(r)
}
s.r = bufr
s.stack = s.stack[:0]
s.size = 0
s.kind = -1
if s.uintbuf == nil {
s.uintbuf = make([]byte, 8)
}
}
// Kind returns the kind and size of the next value in the
// input stream.
//
// The returned size is the number of bytes that make up the value.
// For kind == Byte, the size is zero because the value is
// contained in the type tag.
//
// The first call to Kind will read size information from the input
// reader and leave it positioned at the start of the actual bytes of
// the value. Subsequent calls to Kind (until the value is decoded)
// will not advance the input reader and return cached information.
func (s *Stream) Kind() (kind Kind, size uint64, err error) {
var tos *listpos
if len(s.stack) > 0 {
tos = &s.stack[len(s.stack)-1]
}
if s.kind < 0 {
if tos != nil && tos.pos == tos.size {
return 0, 0, EOL
}
kind, size, err = s.readKind()
if err != nil {
return 0, 0, err
}
s.kind, s.size = kind, size
}
if tos != nil && tos.pos+s.size > tos.size {
return 0, 0, ErrElemTooLarge
}
return s.kind, s.size, nil
}
func (s *Stream) readKind() (kind Kind, size uint64, err error) {
b, err := s.readByte()
if err != nil {
return 0, 0, err
}
s.byteval = 0
switch {
case b < 0x80:
// For a single byte whose value is in the [0x00, 0x7F] range, that byte
// is its own RLP encoding.
s.byteval = b
return Byte, 0, nil
case b < 0xB8:
// Otherwise, if a string is 0-55 bytes long,
// the RLP encoding consists of a single byte with value 0x80 plus the
// length of the string followed by the string. The range of the first
// byte is thus [0x80, 0xB7].
return String, uint64(b - 0x80), nil
case b < 0xC0:
// If a string is more than 55 bytes long, the
// RLP encoding consists of a single byte with value 0xB7 plus the length
// of the length of the string in binary form, followed by the length of
// the string, followed by the string. For example, a length-1024 string
// would be encoded as 0xB90400 followed by the string. The range of
// the first byte is thus [0xB8, 0xBF].
size, err = s.readUint(b - 0xB7)
return String, size, err
case b < 0xF8:
// If the total payload of a list
// (i.e. the combined length of all its items) is 0-55 bytes long, the
// RLP encoding consists of a single byte with value 0xC0 plus the length
// of the list followed by the concatenation of the RLP encodings of the
// items. The range of the first byte is thus [0xC0, 0xF7].
return List, uint64(b - 0xC0), nil
default:
// If the total payload of a list is more than 55 bytes long,
// the RLP encoding consists of a single byte with value 0xF7
// plus the length of the length of the payload in binary
// form, followed by the length of the payload, followed by
// the concatenation of the RLP encodings of the items. The
// range of the first byte is thus [0xF8, 0xFF].
size, err = s.readUint(b - 0xF7)
return List, size, err
}
}
func (s *Stream) readUint(size byte) (uint64, error) {
if size == 1 {
b, err := s.readByte()
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return uint64(b), err
}
start := int(8 - size)
for i := 0; i < start; i++ {
s.uintbuf[i] = 0
}
err := s.readFull(s.uintbuf[start:])
return binary.BigEndian.Uint64(s.uintbuf), err
}
func (s *Stream) readFull(buf []byte) (err error) {
s.willRead(uint64(len(buf)))
var nn, n int
for n < len(buf) && err == nil {
nn, err = s.r.Read(buf[n:])
n += nn
}
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
func (s *Stream) readByte() (byte, error) {
s.willRead(1)
b, err := s.r.ReadByte()
if len(s.stack) > 0 && err == io.EOF {
err = io.ErrUnexpectedEOF
}
return b, err
}
func (s *Stream) willRead(n uint64) {
s.kind = -1 // rearm Kind
if len(s.stack) > 0 {
s.stack[len(s.stack)-1].pos += n
}
}
