// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package rlp
import (
"bufio"
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math/big"
"reflect"
"strings"
"sync"
)
var (
// EOL is returned when the end of the current list
// has been reached during streaming.
EOL = errors.New("rlp: end of list")
// Actual Errors
ErrExpectedString = errors.New("rlp: expected String or Byte")
ErrExpectedList = errors.New("rlp: expected List")
ErrCanonInt = errors.New("rlp: non-canonical integer format")
ErrCanonSize = errors.New("rlp: non-canonical size information")
ErrElemTooLarge = errors.New("rlp: element is larger than containing list")
ErrValueTooLarge = errors.New("rlp: value size exceeds available input length")
ErrMoreThanOneValue = errors.New("rlp: input contains more than one value")
// internal errors
errNotInList = errors.New("rlp: call of ListEnd outside of any list")
errNotAtEOL = errors.New("rlp: call of ListEnd not positioned at EOL")
errUintOverflow = errors.New("rlp: uint overflow")
errNoPointer = errors.New("rlp: interface given to Decode must be a pointer")
errDecodeIntoNil = errors.New("rlp: pointer given to Decode must not be nil")
streamPool = sync.Pool{
New: func() interface{} { return new(Stream) },
}
)
// 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. Please see package-level documentation for the decoding rules. Val must be a
// non-nil pointer.
//
// If r does not implement ByteReader, Decode will do its own buffering.
//
// Note that Decode does not set an input limit for all readers and may be vulnerable to
// panics cause by huge value sizes. If you need an input limit, use
//
// NewStream(r, limit).Decode(val)
func Decode(r io.Reader, val interface{}) error {
stream := streamPool.Get().(*Stream)
defer streamPool.Put(stream)
stream.Reset(r, 0)
return stream.Decode(val)
}
// DecodeBytes parses RLP data from b into val. Please see package-level documentation for
// the decoding rules. The input must contain exactly one value and no trailing data.
func DecodeBytes(b []byte, val interface{}) error {
r := bytes.NewReader(b)
stream := streamPool.Get().(*Stream)
defer streamPool.Put(stream)
stream.Reset(r, uint64(len(b)))
if err := stream.Decode(val); err != nil {
return err
}
if r.Len() > 0 {
return ErrMoreThanOneValue
}
return nil
}
type decodeError struct {
msg string
typ reflect.Type
ctx []string
}
func (err *decodeError) Error() string {
ctx := ""
if len(err.ctx) > 0 {
ctx = ", decoding into "
for i := len(err.ctx) - 1; i >= 0; i-- {
ctx += err.ctx[i]
}
}
return fmt.Sprintf("rlp: %s for %v%s", err.msg, err.typ, ctx)
}
func wrapStreamError(err error, typ reflect.Type) error {
switch err {
case ErrCanonInt:
return &decodeError{msg: "non-canonical integer (leading zero bytes)", typ: typ}
case ErrCanonSize:
return &decodeError{msg: "non-canonical size information", typ: typ}
case ErrExpectedList:
return &decodeError{msg: "expected input list", typ: typ}
case ErrExpectedString:
return &decodeError{msg: "expected input string or byte", typ: typ}
case errUintOverflow:
return &decodeError{msg: "input string too long", typ: typ}
case errNotAtEOL:
return &decodeError{msg: "input list has too many elements", typ: typ}
}
return err
}
func addErrorContext(err error, ctx string) error {
if decErr, ok := err.(*decodeError); ok {
decErr.ctx = append(decErr.ctx, ctx)
}
return err
}
var (
decoderInterface = reflect.TypeOf(new(Decoder)).Elem()
bigInt = reflect.TypeOf(big.Int{})
)
func makeDecoder(typ reflect.Type, tags tags) (dec decoder, err error) {
kind := typ.Kind()
switch {
case typ == rawValueType:
return decodeRawValue, nil
return decodeDecoder, nil
case typ.AssignableTo(reflect.PtrTo(bigInt)):
return decodeBigInt, nil
case typ.AssignableTo(bigInt):
return decodeBigIntNoPtr, nil
case kind == reflect.Ptr:
return makePtrDecoder(typ, tags)
case reflect.PtrTo(typ).Implements(decoderInterface):
return decodeDecoder, nil
case isUint(kind):
return decodeUint, nil
case kind == reflect.Bool:
return decodeBool, nil
case kind == reflect.String:
return decodeString, nil
case kind == reflect.Slice || kind == reflect.Array:
return makeListDecoder(typ, tags)
case kind == reflect.Struct:
return makeStructDecoder(typ)
case kind == reflect.Interface:
return decodeInterface, nil
default:
return nil, fmt.Errorf("rlp: type %v is not RLP-serializable", typ)
}
}
func decodeRawValue(s *Stream, val reflect.Value) error {
r, err := s.Raw()
if err != nil {
return err
}
val.SetBytes(r)
return nil
}
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 decodeBool(s *Stream, val reflect.Value) error {
b, err := s.Bool()
if err != nil {
return wrapStreamError(err, val.Type())
}
val.SetBool(b)
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))
}
// Reject leading zero bytes
if len(b) > 0 && b[0] == 0 {
return wrapStreamError(ErrCanonInt, val.Type())
}
i.SetBytes(b)
return nil
}
func makeListDecoder(typ reflect.Type, tag tags) (decoder, error) {
etype := typ.Elem()
if etype.Kind() == reflect.Uint8 && !reflect.PtrTo(etype).Implements(decoderInterface) {
if typ.Kind() == reflect.Array {
return decodeByteArray, nil
}
return decodeByteSlice, nil
}
etypeinfo := cachedTypeInfo1(etype, tags{})
if etypeinfo.decoderErr != nil {
return nil, etypeinfo.decoderErr
}
var dec decoder
switch {
case typ.Kind() == reflect.Array:
dec = func(s *Stream, val reflect.Value) error {
return decodeListArray(s, val, etypeinfo.decoder)
}
case tag.tail:
// A slice with "tail" tag can occur as the last field
// of a struct and is supposed to swallow all remaining
// list elements. The struct decoder already called s.List,
// proceed directly to decoding the elements.
dec = func(s *Stream, val reflect.Value) error {
return decodeSliceElems(s, val, etypeinfo.decoder)
}
default:
dec = func(s *Stream, val reflect.Value) error {
return decodeListSlice(s, val, etypeinfo.decoder)
}
}
return dec, 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()
}
if err := decodeSliceElems(s, val, elemdec); err != nil {
return err
}
return s.ListEnd()
}
func decodeSliceElems(s *Stream, val reflect.Value, elemdec decoder) error {
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 addErrorContext(err, fmt.Sprint("[", i, "]"))
}
}
if i < val.Len() {
val.SetLen(i)
}
return nil
}
func decodeListArray(s *Stream, val reflect.Value, elemdec decoder) error {
if _, err := s.List(); err != nil {
return wrapStreamError(err, val.Type())
}
vlen := val.Len()
i := 0
for ; i < vlen; i++ {
if err := elemdec(s, val.Index(i)); err == EOL {
break
} else if err != nil {
return addErrorContext(err, fmt.Sprint("[", i, "]"))
}
}
if i < vlen {
return &decodeError{msg: "input list has too few elements", typ: val.Type()}
}
return wrapStreamError(s.ListEnd(), val.Type())
}
func decodeByteSlice(s *Stream, val reflect.Value) error {
b, err := s.Bytes()
if err != nil {
return wrapStreamError(err, val.Type())
}
val.SetBytes(b)
return nil
}
func decodeByteArray(s *Stream, val reflect.Value) error {
kind, size, err := s.Kind()
if err != nil {
return err
}
vlen := val.Len()
switch kind {
case Byte:
if vlen == 0 {
return &decodeError{msg: "input string too long", typ: val.Type()}
}
if vlen > 1 {
return &decodeError{msg: "input string too short", typ: val.Type()}
}
bv, _ := s.Uint()
val.Index(0).SetUint(bv)
case String:
if uint64(vlen) < size {
return &decodeError{msg: "input string too long", typ: val.Type()}
}
if uint64(vlen) > size {
return &decodeError{msg: "input string too short", typ: val.Type()}
}
slice := val.Slice(0, vlen).Interface().([]byte)
if err := s.readFull(slice); err != nil {
return err
}
// Reject cases where single byte encoding should have been used.
if size == 1 && slice[0] < 128 {
return wrapStreamError(ErrCanonSize, val.Type())
}
case List:
return wrapStreamError(ErrExpectedString, val.Type())
}
return nil
}
func makeStructDecoder(typ reflect.Type) (decoder, error) {
fields, err := structFields(typ)
if err != nil {
return nil, err
}
for _, f := range fields {
if f.info.decoderErr != nil {
return nil, structFieldError{typ, f.index, f.info.decoderErr}
}
}
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 {
return &decodeError{msg: "too few elements", typ: typ}
} else if err != nil {
return addErrorContext(err, "."+typ.Field(f.index).Name)
}
}
return wrapStreamError(s.ListEnd(), typ)
}
return dec, nil
}
// makePtrDecoder creates a decoder that decodes into the pointer's element type.
func makePtrDecoder(typ reflect.Type, tag tags) (decoder, error) {
etype := typ.Elem()
etypeinfo := cachedTypeInfo1(etype, tags{})
switch {
case etypeinfo.decoderErr != nil:
return nil, etypeinfo.decoderErr
case !tag.nilOK:
return makeSimplePtrDecoder(etype, etypeinfo), nil
default:
return makeNilPtrDecoder(etype, etypeinfo, tag.nilKind), nil
}
}
func makeSimplePtrDecoder(etype reflect.Type, etypeinfo *typeinfo) decoder {
return func(s *Stream, val reflect.Value) (err error) {
newval := val
if val.IsNil() {
newval = reflect.New(etype)
}
if err = etypeinfo.decoder(s, newval.Elem()); err == nil {
val.Set(newval)
}
return err
}
}
// makeNilPtrDecoder creates a decoder that decodes empty values as nil. Non-empty
// values are decoded into a value of the element type, just like makePtrDecoder does.
//
// This decoder is used for pointer-typed struct fields with struct tag "nil".
func makeNilPtrDecoder(etype reflect.Type, etypeinfo *typeinfo, nilKind Kind) decoder {
typ := reflect.PtrTo(etype)
nilPtr := reflect.Zero(typ)
return func(s *Stream, val reflect.Value) (err error) {
kind, size, err := s.Kind()
if err != nil {
val.Set(nilPtr)
return wrapStreamError(err, typ)
}
// Handle empty values as a nil pointer.
if kind != Byte && size == 0 {
if kind != nilKind {
return &decodeError{
msg: fmt.Sprintf("wrong kind of empty value (got %v, want %v)", kind, nilKind),
typ: typ,
}
}
// rearm s.Kind. This is important because the input
// position must advance to the next value even though
// we don't read anything.
s.kind = -1
val.Set(nilPtr)
return nil
}
newval := val
if val.IsNil() {
newval = reflect.New(etype)
}
if err = etypeinfo.decoder(s, newval.Elem()); err == nil {
val.Set(newval)
}
return err
}
}
var ifsliceType = reflect.TypeOf([]interface{}{})
func decodeInterface(s *Stream, val reflect.Value) error {
if val.Type().NumMethod() != 0 {
return fmt.Errorf("rlp: type %v is not RLP-serializable", val.Type())
}
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
}
func decodeDecoder(s *Stream, val reflect.Value) error {
return val.Addr().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)
}
}
// 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
// number of bytes remaining to be read from r.
remaining uint64
limited bool
// auxiliary buffer for integer decoding
uintbuf []byte
kind Kind // kind of value ahead
size uint64 // size of value ahead
byteval byte // value of single byte in type tag
kinderr error // error from last readKind
stack []listpos
}
type listpos struct{ pos, size uint64 }
// NewStream creates a new decoding stream reading from r.
//
// If r implements the ByteReader interface, Stream will
// not introduce any buffering.
//
// For non-toplevel values, Stream returns ErrElemTooLarge
// for values that do not fit into the enclosing list.
//
// Stream supports an optional input limit. If a limit is set, the
// size of any toplevel value will be checked against the remaining
// input length. Stream operations that encounter a value exceeding
// the remaining input length will return ErrValueTooLarge. The limit
// can be set by passing a non-zero value for inputLimit.
//
// If r is a bytes.Reader or strings.Reader, the input limit is set to
// the length of r's underlying data unless an explicit limit is
// provided.
func NewStream(r io.Reader, inputLimit uint64) *Stream {
s := new(Stream)
s.Reset(r, inputLimit)
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, len)
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
}
if size == 1 && b[0] < 128 {
return nil, ErrCanonSize
}
return b, nil
default:
return nil, ErrExpectedString
}
}
// Raw reads a raw encoded value including RLP type information.
func (s *Stream) Raw() ([]byte, error) {
kind, size, err := s.Kind()
if err != nil {
return nil, err
}
if kind == Byte {
s.kind = -1 // rearm Kind
return []byte{s.byteval}, nil
}
// the original header has already been read and is no longer
// available. read content and put a new header in front of it.
start := headsize(size)
buf := make([]byte, uint64(start)+size)
if err := s.readFull(buf[start:]); err != nil {
return nil, err
}
if kind == String {
puthead(buf, 0x80, 0xB7, size)
} else {
puthead(buf, 0xC0, 0xF7, size)
}
return buf, nil
}
// 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:
if s.byteval == 0 {
return 0, ErrCanonInt
}
s.kind = -1 // rearm Kind
return uint64(s.byteval), nil
case String:
if size > uint64(maxbits/8) {
return 0, errUintOverflow
}
v, err := s.readUint(byte(size))
switch {
case err == ErrCanonSize:
// Adjust error because we're not reading a size right now.
return 0, ErrCanonInt
case err != nil:
return 0, err
case size > 0 && v < 128:
return 0, ErrCanonSize
default:
return v, nil
}
default:
return 0, ErrExpectedString
}
}
// Bool reads an RLP string of up to 1 byte and returns its contents
// as a boolean. If the input does not contain an RLP string, the
// returned error will be ErrExpectedString.
func (s *Stream) Bool() (bool, error) {
num, err := s.uint(8)
if err != nil {
return false, err
}
switch num {
case 0:
return false, nil
case 1:
return true, nil
default:
return false, fmt.Errorf("rlp: invalid boolean value: %d", num)
}
}
// 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
}
decoder, err := cachedDecoder(rtyp.Elem())
if err != nil {
return err
}
err = decoder(s, rval.Elem())
if decErr, ok := err.(*decodeError); ok && len(decErr.ctx) > 0 {
// add decode target type to error so context has more meaning
decErr.ctx = append(decErr.ctx, fmt.Sprint("(", rtyp.Elem(), ")"))
}
return err
}
// Reset discards any information about the current decoding context
// and starts reading from r. This method is meant to facilitate reuse
// of a preallocated Stream across many decoding operations.
//
// If r does not also implement ByteReader, Stream will do its own
// buffering.
func (s *Stream) Reset(r io.Reader, inputLimit uint64) {
if inputLimit > 0 {
s.remaining = inputLimit
s.limited = true
} else {
// Attempt to automatically discover
// the limit when reading from a byte slice.
switch br := r.(type) {
case *bytes.Reader:
s.remaining = uint64(br.Len())
s.limited = true
case *strings.Reader:
s.remaining = uint64(br.Len())
s.limited = true
default:
s.limited = false
}
}
// Wrap r with a buffer if it doesn't have one.
bufr, ok := r.(ByteReader)
if !ok {
bufr = bufio.NewReader(r)
}
s.r = bufr
// Reset the decoding context.
s.stack = s.stack[:0]
s.size = 0
s.kind = -1
s.kinderr = nil
if s.uintbuf == nil {
s.uintbuf = make([]byte, 8)
}
s.byteval = 0
}
// 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 {
s.kinderr = nil
// Don't read further if we're at the end of the
// innermost list.
if tos != nil && tos.pos == tos.size {
return 0, 0, EOL
}
s.kind, s.size, s.kinderr = s.readKind()
if s.kinderr == nil {
if tos == nil {
// At toplevel, check that the value is smaller
// than the remaining input length.
if s.limited && s.size > s.remaining {
s.kinderr = ErrValueTooLarge
}
} else {
// Inside a list, check that the value doesn't overflow the list.
if s.size > tos.size-tos.pos {
s.kinderr = ErrElemTooLarge
}
}
}
}
// Note: this might return a sticky error generated
// by an earlier call to readKind.
return s.kind, s.size, s.kinderr
}
func (s *Stream) readKind() (kind Kind, size uint64, err error) {
b, err := s.readByte()
if err != nil {
if len(s.stack) == 0 {
// At toplevel, Adjust the error to actual EOF. io.EOF is
// used by callers to determine when to stop decoding.
switch err {
case io.ErrUnexpectedEOF:
err = io.EOF
case ErrValueTooLarge:
err = io.EOF
}
}
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)
if err == nil && size < 56 {
err = ErrCanonSize
}
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)
if err == nil && size < 56 {
err = ErrCanonSize
}
return List, size, err
}
}
func (s *Stream) readUint(size byte) (uint64, error) {
switch size {
case 0:
s.kind = -1 // rearm Kind
return 0, nil
case 1:
b, err := s.readByte()
return uint64(b), err
default:
start := int(8 - size)
for i := 0; i < start; i++ {
s.uintbuf[i] = 0
}
if err := s.readFull(s.uintbuf[start:]); err != nil {
return 0, err
}
if s.uintbuf[start] == 0 {
// Note: readUint is also used to decode integer
// values. The error needs to be adjusted to become
// ErrCanonInt in this case.
return 0, ErrCanonSize
}
return binary.BigEndian.Uint64(s.uintbuf), nil
}
}
func (s *Stream) readFull(buf []byte) (err error) {
if err := s.willRead(uint64(len(buf))); err != nil {
return err
}
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) {
if err := s.willRead(1); err != nil {
return 0, err
}
b, err := s.r.ReadByte()
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return b, err
}
func (s *Stream) willRead(n uint64) error {
s.kind = -1 // rearm Kind
if len(s.stack) > 0 {
// check list overflow
tos := s.stack[len(s.stack)-1]
if n > tos.size-tos.pos {
return ErrElemTooLarge
}
s.stack[len(s.stack)-1].pos += n
}
if s.limited {
if n > s.remaining {
return ErrValueTooLarge
}
s.remaining -= n
}
return nil
}
