rlp包加入

rlp/decode.go

@@ -0,0 +1,1024 @@
+// 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"
+)
+
+//lint:ignore ST1012 EOL is not an error.
+
+// EOL is returned when the end of the current list
+// has been reached during streaming.
+var EOL = errors.New("rlp: end of list")
+
+var (
+	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
+	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 {
+	var buffer []byte
+	kind, size, err := s.Kind()
+	switch {
+	case err != nil:
+		return wrapStreamError(err, val.Type())
+	case kind == List:
+		return wrapStreamError(ErrExpectedString, val.Type())
+	case kind == Byte:
+		buffer = s.uintbuf[:1]
+		buffer[0] = s.byteval
+		s.kind = -1 // re-arm Kind
+	case size == 0:
+		// Avoid zero-length read.
+		s.kind = -1
+	case size <= uint64(len(s.uintbuf)):
+		// For integers smaller than s.uintbuf, allocating a buffer
+		// can be avoided.
+		buffer = s.uintbuf[:size]
+		if err := s.readFull(buffer); err != nil {
+			return wrapStreamError(err, val.Type())
+		}
+		// Reject inputs where single byte encoding should have been used.
+		if size == 1 && buffer[0] < 128 {
+			return wrapStreamError(ErrCanonSize, val.Type())
+		}
+	default:
+		// For large integers, a temporary buffer is needed.
+		buffer = make([]byte, size)
+		if err := s.readFull(buffer); err != nil {
+			return wrapStreamError(err, val.Type())
+		}
+	}
+
+	// Reject leading zero bytes.
+	if len(buffer) > 0 && buffer[0] == 0 {
+		return wrapStreamError(ErrCanonInt, val.Type())
+	}
+
+	// Set the integer bytes.
+	i := val.Interface().(*big.Int)
+	if i == nil {
+		i = new(big.Int)
+		val.Set(reflect.ValueOf(i))
+	}
+	i.SetBytes(buffer)
+	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 := theTC.infoWhileGenerating(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
+	}
+	slice := byteArrayBytes(val)
+	switch kind {
+	case Byte:
+		if len(slice) == 0 {
+			return &decodeError{msg: "input string too long", typ: val.Type()}
+		} else if len(slice) > 1 {
+			return &decodeError{msg: "input string too short", typ: val.Type()}
+		}
+		slice[0] = s.byteval
+		s.kind = -1
+	case String:
+		if uint64(len(slice)) < size {
+			return &decodeError{msg: "input string too long", typ: val.Type()}
+		}
+		if uint64(len(slice)) > size {
+			return &decodeError{msg: "input string too short", typ: val.Type()}
+		}
+		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 := theTC.infoWhileGenerating(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 int8
+
+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
+
+	remaining uint64   // number of bytes remaining to be read from r
+	size      uint64   // size of value ahead
+	kinderr   error    // error from last readKind
+	stack     []uint64 // list sizes
+	uintbuf   [32]byte // auxiliary buffer for integer decoding
+	kind      Kind     // kind of value ahead
+	byteval   byte     // value of single byte in type tag
+	limited   bool     // true if input limit is in effect
+}
+
+// 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
+	}
+
+	// Remove size of inner list from outer list before pushing the new size
+	// onto the stack. This ensures that the remaining outer list size will
+	// be correct after the matching call to ListEnd.
+	if inList, limit := s.listLimit(); inList {
+		s.stack[len(s.stack)-1] = limit - size
+	}
+	s.stack = append(s.stack, 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 {
+	// Ensure that no more data is remaining in the current list.
+	if inList, listLimit := s.listLimit(); !inList {
+		return errNotInList
+	} else if listLimit > 0 {
+		return errNotAtEOL
+	}
+	s.stack = s.stack[:len(s.stack)-1] // pop
+	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 *bytes.Buffer:
+			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
+	s.byteval = 0
+	s.uintbuf = [32]byte{}
+}
+
+// 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) {
+	if s.kind >= 0 {
+		return s.kind, s.size, s.kinderr
+	}
+
+	// Check for end of list. This needs to be done here because readKind
+	// checks against the list size, and would return the wrong error.
+	inList, listLimit := s.listLimit()
+	if inList && listLimit == 0 {
+		return 0, 0, EOL
+	}
+	// Read the actual size tag.
+	s.kind, s.size, s.kinderr = s.readKind()
+	if s.kinderr == nil {
+		// Check the data size of the value ahead against input limits. This
+		// is done here because many decoders require allocating an input
+		// buffer matching the value size. Checking it here protects those
+		// decoders from inputs declaring very large value size.
+		if inList && s.size > listLimit {
+			s.kinderr = ErrElemTooLarge
+		} else if s.limited && s.size > s.remaining {
+			s.kinderr = ErrValueTooLarge
+		}
+	}
+	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:
+		buffer := s.uintbuf[:8]
+		for i := range buffer {
+			buffer[i] = 0
+		}
+		start := int(8 - size)
+		if err := s.readFull(buffer[start:]); err != nil {
+			return 0, err
+		}
+		if buffer[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(buffer[:]), nil
+	}
+}
+
+// readFull reads into buf from the underlying stream.
+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 {
+		if n < len(buf) {
+			err = io.ErrUnexpectedEOF
+		} else {
+			// Readers are allowed to give EOF even though the read succeeded.
+			// In such cases, we discard the EOF, like io.ReadFull() does.
+			err = nil
+		}
+	}
+	return err
+}
+
+// readByte reads a single byte from the underlying stream.
+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
+}
+
+// willRead is called before any read from the underlying stream. It checks
+// n against size limits, and updates the limits if n doesn't overflow them.
+func (s *Stream) willRead(n uint64) error {
+	s.kind = -1 // rearm Kind
+
+	if inList, limit := s.listLimit(); inList {
+		if n > limit {
+			return ErrElemTooLarge
+		}
+		s.stack[len(s.stack)-1] = limit - n
+	}
+	if s.limited {
+		if n > s.remaining {
+			return ErrValueTooLarge
+		}
+		s.remaining -= n
+	}
+	return nil
+}
+
+// listLimit returns the amount of data remaining in the innermost list.
+func (s *Stream) listLimit() (inList bool, limit uint64) {
+	if len(s.stack) == 0 {
+		return false, 0
+	}
+	return true, s.stack[len(s.stack)-1]
+}

rlp/doc.go

@@ -0,0 +1,130 @@
+// 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 implements the RLP serialization format.
+
+The purpose of RLP (Recursive Linear Prefix) is to encode arbitrarily nested arrays of
+binary data, and RLP is the main encoding method used to serialize objects in Ethereum.
+The only purpose of RLP is to encode structure; encoding specific atomic data types (eg.
+strings, ints, floats) is left up to higher-order protocols. In Ethereum integers must be
+represented in big endian binary form with no leading zeroes (thus making the integer
+value zero equivalent to the empty string).
+
+RLP values are distinguished by a type tag. The type tag precedes the value in the input
+stream and defines the size and kind of the bytes that follow.
+
+
+Encoding Rules
+
+Package rlp uses reflection and encodes RLP based on the Go type of the value.
+
+If the type implements the Encoder interface, Encode calls EncodeRLP. It does not
+call EncodeRLP on nil pointer values.
+
+To encode a pointer, the value being pointed to is encoded. A nil pointer to a struct
+type, slice or array always encodes as an empty RLP list unless the slice or array has
+elememt type byte. A nil pointer to any other value encodes as the empty string.
+
+Struct values are encoded as an RLP list of all their encoded public fields. Recursive
+struct types are supported.
+
+To encode slices and arrays, the elements are encoded as an RLP list of the value's
+elements. Note that arrays and slices with element type uint8 or byte are always encoded
+as an RLP string.
+
+A Go string is encoded as an RLP string.
+
+An unsigned integer value is encoded as an RLP string. Zero always encodes as an empty RLP
+string. big.Int values are treated as integers. Signed integers (int, int8, int16, ...)
+are not supported and will return an error when encoding.
+
+Boolean values are encoded as the unsigned integers zero (false) and one (true).
+
+An interface value encodes as the value contained in the interface.
+
+Floating point numbers, maps, channels and functions are not supported.
+
+
+Decoding Rules
+
+Decoding uses the following type-dependent rules:
+
+If the type implements the Decoder interface, DecodeRLP is called.
+
+To decode into a pointer, the value will be decoded as the element type of the pointer. If
+the pointer is nil, a new value of the pointer's element type is allocated. If the pointer
+is non-nil, the existing value will be reused. Note that package rlp never leaves a
+pointer-type struct field as nil unless one of the "nil" struct tags is present.
+
+To decode into a struct, decoding 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. The input list must contain an element for each decoded field. Decoding
+returns an error if there are too few or too many elements for the struct.
+
+To decode into a slice, the input must be a list and the resulting slice will contain the
+input elements in order. For byte slices, the input must be an RLP string. Array types
+decode similarly, with the additional restriction that the number of input elements (or
+bytes) must match the array's defined length.
+
+To decode into a Go string, the input must be an RLP string. The input 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, decoding will return an error. Decode also supports
+*big.Int. There is no size limit for big integers.
+
+To decode into a boolean, the input must contain an unsigned integer of value zero (false)
+or one (true).
+
+To decode into an interface value, one of these types is stored in the value:
+
+	  []interface{}, for RLP lists
+	  []byte, for RLP strings
+
+Non-empty interface types are not supported when decoding.
+Signed integers, floating point numbers, maps, channels and functions cannot be decoded into.
+
+
+Struct Tags
+
+Package rlp honours certain struct tags: "-", "tail", "nil", "nilList" and "nilString".
+
+The "-" tag ignores fields.
+
+The "tail" tag, which may only be used on the last exported struct field, allows slurping
+up any excess list elements into a slice. See examples for more details.
+
+The "nil" tag applies to pointer-typed fields and changes the decoding rules for the field
+such that input values of size zero decode as a nil pointer. This tag can be useful when
+decoding recursive types.
+
+    type StructWithOptionalFoo struct {
+        Foo *[20]byte `rlp:"nil"`
+    }
+
+RLP supports two kinds of empty values: empty lists and empty strings. When using the
+"nil" tag, the kind of empty value allowed for a type is chosen automatically. A struct
+field whose Go type is a pointer to an unsigned integer, string, boolean or byte
+array/slice expects an empty RLP string. Any other pointer field type encodes/decodes as
+an empty RLP list.
+
+The choice of null value can be made explicit with the "nilList" and "nilString" struct
+tags. Using these tags encodes/decodes a Go nil pointer value as the kind of empty
+RLP value defined by the tag.
+*/
+package rlp

rlp/encode.go

@@ -0,0 +1,651 @@
+// 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 (
+	"fmt"
+	"io"
+	"math/big"
+	"reflect"
+	"sync"
+)
+
+var (
+	// Common encoded values.
+	// These are useful when implementing EncodeRLP.
+	EmptyString = []byte{0x80}
+	EmptyList   = []byte{0xC0}
+)
+
+// Encoder is implemented by types that require custom
+// encoding rules or want to encode private fields.
+type Encoder interface {
+	// EncodeRLP should write the RLP encoding of its receiver to w.
+	// If the implementation is a pointer method, it may also be
+	// called for nil pointers.
+	//
+	// Implementations should generate valid RLP. The data written is
+	// not verified at the moment, but a future version might. It is
+	// recommended to write only a single value but writing multiple
+	// values or no value at all is also permitted.
+	EncodeRLP(io.Writer) error
+}
+
+// Encode writes the RLP encoding of val to w. Note that Encode may
+// perform many small writes in some cases. Consider making w
+// buffered.
+//
+// Please see package-level documentation of encoding rules.
+func Encode(w io.Writer, val interface{}) error {
+	if outer, ok := w.(*encbuf); ok {
+		// Encode was called by some type's EncodeRLP.
+		// Avoid copying by writing to the outer encbuf directly.
+		return outer.encode(val)
+	}
+	eb := encbufPool.Get().(*encbuf)
+	defer encbufPool.Put(eb)
+	eb.reset()
+	if err := eb.encode(val); err != nil {
+		return err
+	}
+	return eb.toWriter(w)
+}
+
+// EncodeToBytes returns the RLP encoding of val.
+// Please see package-level documentation for the encoding rules.
+func EncodeToBytes(val interface{}) ([]byte, error) {
+	eb := encbufPool.Get().(*encbuf)
+	defer encbufPool.Put(eb)
+	eb.reset()
+	if err := eb.encode(val); err != nil {
+		return nil, err
+	}
+	return eb.toBytes(), nil
+}
+
+// EncodeToReader returns a reader from which the RLP encoding of val
+// can be read. The returned size is the total size of the encoded
+// data.
+//
+// Please see the documentation of Encode for the encoding rules.
+func EncodeToReader(val interface{}) (size int, r io.Reader, err error) {
+	eb := encbufPool.Get().(*encbuf)
+	eb.reset()
+	if err := eb.encode(val); err != nil {
+		return 0, nil, err
+	}
+	return eb.size(), &encReader{buf: eb}, nil
+}
+
+type listhead struct {
+	offset int // index of this header in string data
+	size   int // total size of encoded data (including list headers)
+}
+
+// encode writes head to the given buffer, which must be at least
+// 9 bytes long. It returns the encoded bytes.
+func (head *listhead) encode(buf []byte) []byte {
+	return buf[:puthead(buf, 0xC0, 0xF7, uint64(head.size))]
+}
+
+// headsize returns the size of a list or string header
+// for a value of the given size.
+func headsize(size uint64) int {
+	if size < 56 {
+		return 1
+	}
+	return 1 + intsize(size)
+}
+
+// puthead writes a list or string header to buf.
+// buf must be at least 9 bytes long.
+func puthead(buf []byte, smalltag, largetag byte, size uint64) int {
+	if size < 56 {
+		buf[0] = smalltag + byte(size)
+		return 1
+	}
+	sizesize := putint(buf[1:], size)
+	buf[0] = largetag + byte(sizesize)
+	return sizesize + 1
+}
+
+type encbuf struct {
+	str     []byte     // string data, contains everything except list headers
+	lheads  []listhead // all list headers
+	lhsize  int        // sum of sizes of all encoded list headers
+	sizebuf [9]byte    // auxiliary buffer for uint encoding
+}
+
+// encbufs are pooled.
+var encbufPool = sync.Pool{
+	New: func() interface{} { return new(encbuf) },
+}
+
+func (w *encbuf) reset() {
+	w.lhsize = 0
+	w.str = w.str[:0]
+	w.lheads = w.lheads[:0]
+}
+
+// encbuf implements io.Writer so it can be passed it into EncodeRLP.
+func (w *encbuf) Write(b []byte) (int, error) {
+	w.str = append(w.str, b...)
+	return len(b), nil
+}
+
+func (w *encbuf) encode(val interface{}) error {
+	rval := reflect.ValueOf(val)
+	writer, err := cachedWriter(rval.Type())
+	if err != nil {
+		return err
+	}
+	return writer(rval, w)
+}
+
+func (w *encbuf) encodeStringHeader(size int) {
+	if size < 56 {
+		w.str = append(w.str, 0x80+byte(size))
+	} else {
+		sizesize := putint(w.sizebuf[1:], uint64(size))
+		w.sizebuf[0] = 0xB7 + byte(sizesize)
+		w.str = append(w.str, w.sizebuf[:sizesize+1]...)
+	}
+}
+
+func (w *encbuf) encodeString(b []byte) {
+	if len(b) == 1 && b[0] <= 0x7F {
+		// fits single byte, no string header
+		w.str = append(w.str, b[0])
+	} else {
+		w.encodeStringHeader(len(b))
+		w.str = append(w.str, b...)
+	}
+}
+
+func (w *encbuf) encodeUint(i uint64) {
+	if i == 0 {
+		w.str = append(w.str, 0x80)
+	} else if i < 128 {
+		// fits single byte
+		w.str = append(w.str, byte(i))
+	} else {
+		s := putint(w.sizebuf[1:], i)
+		w.sizebuf[0] = 0x80 + byte(s)
+		w.str = append(w.str, w.sizebuf[:s+1]...)
+	}
+}
+
+// list adds a new list header to the header stack. It returns the index
+// of the header. The caller must call listEnd with this index after encoding
+// the content of the list.
+func (w *encbuf) list() int {
+	w.lheads = append(w.lheads, listhead{offset: len(w.str), size: w.lhsize})
+	return len(w.lheads) - 1
+}
+
+func (w *encbuf) listEnd(index int) {
+	lh := &w.lheads[index]
+	lh.size = w.size() - lh.offset - lh.size
+	if lh.size < 56 {
+		w.lhsize++ // length encoded into kind tag
+	} else {
+		w.lhsize += 1 + intsize(uint64(lh.size))
+	}
+}
+
+func (w *encbuf) size() int {
+	return len(w.str) + w.lhsize
+}
+
+func (w *encbuf) toBytes() []byte {
+	out := make([]byte, w.size())
+	strpos := 0
+	pos := 0
+	for _, head := range w.lheads {
+		// write string data before header
+		n := copy(out[pos:], w.str[strpos:head.offset])
+		pos += n
+		strpos += n
+		// write the header
+		enc := head.encode(out[pos:])
+		pos += len(enc)
+	}
+	// copy string data after the last list header
+	copy(out[pos:], w.str[strpos:])
+	return out
+}
+
+func (w *encbuf) toWriter(out io.Writer) (err error) {
+	strpos := 0
+	for _, head := range w.lheads {
+		// write string data before header
+		if head.offset-strpos > 0 {
+			n, err := out.Write(w.str[strpos:head.offset])
+			strpos += n
+			if err != nil {
+				return err
+			}
+		}
+		// write the header
+		enc := head.encode(w.sizebuf[:])
+		if _, err = out.Write(enc); err != nil {
+			return err
+		}
+	}
+	if strpos < len(w.str) {
+		// write string data after the last list header
+		_, err = out.Write(w.str[strpos:])
+	}
+	return err
+}
+
+// encReader is the io.Reader returned by EncodeToReader.
+// It releases its encbuf at EOF.
+type encReader struct {
+	buf    *encbuf // the buffer we're reading from. this is nil when we're at EOF.
+	lhpos  int     // index of list header that we're reading
+	strpos int     // current position in string buffer
+	piece  []byte  // next piece to be read
+}
+
+func (r *encReader) Read(b []byte) (n int, err error) {
+	for {
+		if r.piece = r.next(); r.piece == nil {
+			// Put the encode buffer back into the pool at EOF when it
+			// is first encountered. Subsequent calls still return EOF
+			// as the error but the buffer is no longer valid.
+			if r.buf != nil {
+				encbufPool.Put(r.buf)
+				r.buf = nil
+			}
+			return n, io.EOF
+		}
+		nn := copy(b[n:], r.piece)
+		n += nn
+		if nn < len(r.piece) {
+			// piece didn't fit, see you next time.
+			r.piece = r.piece[nn:]
+			return n, nil
+		}
+		r.piece = nil
+	}
+}
+
+// next returns the next piece of data to be read.
+// it returns nil at EOF.
+func (r *encReader) next() []byte {
+	switch {
+	case r.buf == nil:
+		return nil
+
+	case r.piece != nil:
+		// There is still data available for reading.
+		return r.piece
+
+	case r.lhpos < len(r.buf.lheads):
+		// We're before the last list header.
+		head := r.buf.lheads[r.lhpos]
+		sizebefore := head.offset - r.strpos
+		if sizebefore > 0 {
+			// String data before header.
+			p := r.buf.str[r.strpos:head.offset]
+			r.strpos += sizebefore
+			return p
+		}
+		r.lhpos++
+		return head.encode(r.buf.sizebuf[:])
+
+	case r.strpos < len(r.buf.str):
+		// String data at the end, after all list headers.
+		p := r.buf.str[r.strpos:]
+		r.strpos = len(r.buf.str)
+		return p
+
+	default:
+		return nil
+	}
+}
+
+var encoderInterface = reflect.TypeOf(new(Encoder)).Elem()
+
+// makeWriter creates a writer function for the given type.
+func makeWriter(typ reflect.Type, ts tags) (writer, error) {
+	kind := typ.Kind()
+	switch {
+	case typ == rawValueType:
+		return writeRawValue, nil
+	case typ.AssignableTo(reflect.PtrTo(bigInt)):
+		return writeBigIntPtr, nil
+	case typ.AssignableTo(bigInt):
+		return writeBigIntNoPtr, nil
+	case kind == reflect.Ptr:
+		return makePtrWriter(typ, ts)
+	case reflect.PtrTo(typ).Implements(encoderInterface):
+		return makeEncoderWriter(typ), nil
+	case isUint(kind):
+		return writeUint, nil
+	case kind == reflect.Bool:
+		return writeBool, nil
+	case kind == reflect.String:
+		return writeString, nil
+	case kind == reflect.Slice && isByte(typ.Elem()):
+		return writeBytes, nil
+	case kind == reflect.Array && isByte(typ.Elem()):
+		return makeByteArrayWriter(typ), nil
+	case kind == reflect.Slice || kind == reflect.Array:
+		return makeSliceWriter(typ, ts)
+	case kind == reflect.Struct:
+		return makeStructWriter(typ)
+	case kind == reflect.Interface:
+		return writeInterface, nil
+	default:
+		return nil, fmt.Errorf("rlp: type %v is not RLP-serializable", typ)
+	}
+}
+
+func writeRawValue(val reflect.Value, w *encbuf) error {
+	w.str = append(w.str, val.Bytes()...)
+	return nil
+}
+
+func writeUint(val reflect.Value, w *encbuf) error {
+	w.encodeUint(val.Uint())
+	return nil
+}
+
+func writeBool(val reflect.Value, w *encbuf) error {
+	if val.Bool() {
+		w.str = append(w.str, 0x01)
+	} else {
+		w.str = append(w.str, 0x80)
+	}
+	return nil
+}
+
+func writeBigIntPtr(val reflect.Value, w *encbuf) error {
+	ptr := val.Interface().(*big.Int)
+	if ptr == nil {
+		w.str = append(w.str, 0x80)
+		return nil
+	}
+	return writeBigInt(ptr, w)
+}
+
+func writeBigIntNoPtr(val reflect.Value, w *encbuf) error {
+	i := val.Interface().(big.Int)
+	return writeBigInt(&i, w)
+}
+
+// wordBytes is the number of bytes in a big.Word
+const wordBytes = (32 << (uint64(^big.Word(0)) >> 63)) / 8
+
+func writeBigInt(i *big.Int, w *encbuf) error {
+	if i.Sign() == -1 {
+		return fmt.Errorf("rlp: cannot encode negative *big.Int")
+	}
+	bitlen := i.BitLen()
+	if bitlen <= 64 {
+		w.encodeUint(i.Uint64())
+		return nil
+	}
+	// Integer is larger than 64 bits, encode from i.Bits().
+	// The minimal byte length is bitlen rounded up to the next
+	// multiple of 8, divided by 8.
+	length := ((bitlen + 7) & -8) >> 3
+	w.encodeStringHeader(length)
+	w.str = append(w.str, make([]byte, length)...)
+	index := length
+	buf := w.str[len(w.str)-length:]
+	for _, d := range i.Bits() {
+		for j := 0; j < wordBytes && index > 0; j++ {
+			index--
+			buf[index] = byte(d)
+			d >>= 8
+		}
+	}
+	return nil
+}
+
+func writeBytes(val reflect.Value, w *encbuf) error {
+	w.encodeString(val.Bytes())
+	return nil
+}
+
+func makeByteArrayWriter(typ reflect.Type) writer {
+	switch typ.Len() {
+	case 0:
+		return writeLengthZeroByteArray
+	case 1:
+		return writeLengthOneByteArray
+	default:
+		return writeByteArray
+	}
+}
+
+func writeLengthZeroByteArray(val reflect.Value, w *encbuf) error {
+	w.str = append(w.str, 0x80)
+	return nil
+}
+
+func writeLengthOneByteArray(val reflect.Value, w *encbuf) error {
+	b := byte(val.Index(0).Uint())
+	if b <= 0x7f {
+		w.str = append(w.str, b)
+	} else {
+		w.str = append(w.str, 0x81, b)
+	}
+	return nil
+}
+
+func writeByteArray(val reflect.Value, w *encbuf) error {
+	if !val.CanAddr() {
+		// Getting the byte slice of val requires it to be addressable. Make it
+		// addressable by copying.
+		copy := reflect.New(val.Type()).Elem()
+		copy.Set(val)
+		val = copy
+	}
+
+	slice := byteArrayBytes(val)
+	w.encodeStringHeader(len(slice))
+	w.str = append(w.str, slice...)
+	return nil
+}
+
+func writeString(val reflect.Value, w *encbuf) error {
+	s := val.String()
+	if len(s) == 1 && s[0] <= 0x7f {
+		// fits single byte, no string header
+		w.str = append(w.str, s[0])
+	} else {
+		w.encodeStringHeader(len(s))
+		w.str = append(w.str, s...)
+	}
+	return nil
+}
+
+func writeInterface(val reflect.Value, w *encbuf) error {
+	if val.IsNil() {
+		// Write empty list. This is consistent with the previous RLP
+		// encoder that we had and should therefore avoid any
+		// problems.
+		w.str = append(w.str, 0xC0)
+		return nil
+	}
+	eval := val.Elem()
+	writer, err := cachedWriter(eval.Type())
+	if err != nil {
+		return err
+	}
+	return writer(eval, w)
+}
+
+func makeSliceWriter(typ reflect.Type, ts tags) (writer, error) {
+	etypeinfo := theTC.infoWhileGenerating(typ.Elem(), tags{})
+	if etypeinfo.writerErr != nil {
+		return nil, etypeinfo.writerErr
+	}
+	writer := func(val reflect.Value, w *encbuf) error {
+		if !ts.tail {
+			defer w.listEnd(w.list())
+		}
+		vlen := val.Len()
+		for i := 0; i < vlen; i++ {
+			if err := etypeinfo.writer(val.Index(i), w); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+	return writer, nil
+}
+
+func makeStructWriter(typ reflect.Type) (writer, error) {
+	fields, err := structFields(typ)
+	if err != nil {
+		return nil, err
+	}
+	for _, f := range fields {
+		if f.info.writerErr != nil {
+			return nil, structFieldError{typ, f.index, f.info.writerErr}
+		}
+	}
+	writer := func(val reflect.Value, w *encbuf) error {
+		lh := w.list()
+		for _, f := range fields {
+			if err := f.info.writer(val.Field(f.index), w); err != nil {
+				return err
+			}
+		}
+		w.listEnd(lh)
+		return nil
+	}
+	return writer, nil
+}
+
+func makePtrWriter(typ reflect.Type, ts tags) (writer, error) {
+	etypeinfo := theTC.infoWhileGenerating(typ.Elem(), tags{})
+	if etypeinfo.writerErr != nil {
+		return nil, etypeinfo.writerErr
+	}
+	// Determine how to encode nil pointers.
+	var nilKind Kind
+	if ts.nilOK {
+		nilKind = ts.nilKind // use struct tag if provided
+	} else {
+		nilKind = defaultNilKind(typ.Elem())
+	}
+
+	writer := func(val reflect.Value, w *encbuf) error {
+		if val.IsNil() {
+			if nilKind == String {
+				w.str = append(w.str, 0x80)
+			} else {
+				w.listEnd(w.list())
+			}
+			return nil
+		}
+		return etypeinfo.writer(val.Elem(), w)
+	}
+	return writer, nil
+}
+
+func makeEncoderWriter(typ reflect.Type) writer {
+	if typ.Implements(encoderInterface) {
+		return func(val reflect.Value, w *encbuf) error {
+			return val.Interface().(Encoder).EncodeRLP(w)
+		}
+	}
+	w := func(val reflect.Value, w *encbuf) error {
+		if !val.CanAddr() {
+			// package json simply doesn't call MarshalJSON for this case, but encodes the
+			// value as if it didn't implement the interface. We don't want to handle it that
+			// way.
+			return fmt.Errorf("rlp: unadressable value of type %v, EncodeRLP is pointer method", val.Type())
+		}
+		return val.Addr().Interface().(Encoder).EncodeRLP(w)
+	}
+	return w
+}
+
+// putint writes i to the beginning of b in big endian byte
+// order, using the least number of bytes needed to represent i.
+func putint(b []byte, i uint64) (size int) {
+	switch {
+	case i < (1 << 8):
+		b[0] = byte(i)
+		return 1
+	case i < (1 << 16):
+		b[0] = byte(i >> 8)
+		b[1] = byte(i)
+		return 2
+	case i < (1 << 24):
+		b[0] = byte(i >> 16)
+		b[1] = byte(i >> 8)
+		b[2] = byte(i)
+		return 3
+	case i < (1 << 32):
+		b[0] = byte(i >> 24)
+		b[1] = byte(i >> 16)
+		b[2] = byte(i >> 8)
+		b[3] = byte(i)
+		return 4
+	case i < (1 << 40):
+		b[0] = byte(i >> 32)
+		b[1] = byte(i >> 24)
+		b[2] = byte(i >> 16)
+		b[3] = byte(i >> 8)
+		b[4] = byte(i)
+		return 5
+	case i < (1 << 48):
+		b[0] = byte(i >> 40)
+		b[1] = byte(i >> 32)
+		b[2] = byte(i >> 24)
+		b[3] = byte(i >> 16)
+		b[4] = byte(i >> 8)
+		b[5] = byte(i)
+		return 6
+	case i < (1 << 56):
+		b[0] = byte(i >> 48)
+		b[1] = byte(i >> 40)
+		b[2] = byte(i >> 32)
+		b[3] = byte(i >> 24)
+		b[4] = byte(i >> 16)
+		b[5] = byte(i >> 8)
+		b[6] = byte(i)
+		return 7
+	default:
+		b[0] = byte(i >> 56)
+		b[1] = byte(i >> 48)
+		b[2] = byte(i >> 40)
+		b[3] = byte(i >> 32)
+		b[4] = byte(i >> 24)
+		b[5] = byte(i >> 16)
+		b[6] = byte(i >> 8)
+		b[7] = byte(i)
+		return 8
+	}
+}
+
+// intsize computes the minimum number of bytes required to store i.
+func intsize(i uint64) (size int) {
+	for size = 1; ; size++ {
+		if i >>= 8; i == 0 {
+			return size
+		}
+	}
+}

rlp/iterator.go

@@ -0,0 +1,61 @@
+// Copyright 2019 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
+
+type listIterator struct {
+	data []byte
+	next []byte
+	err  error
+}
+
+// NewListIterator creates an iterator for the (list) represented by data
+// TODO: Consider removing this implementation, as it is no longer used.
+func NewListIterator(data RawValue) (*listIterator, error) {
+	k, t, c, err := readKind(data)
+	if err != nil {
+		return nil, err
+	}
+	if k != List {
+		return nil, ErrExpectedList
+	}
+	it := &listIterator{
+		data: data[t : t+c],
+	}
+	return it, nil
+
+}
+
+// Next forwards the iterator one step, returns true if it was not at end yet
+func (it *listIterator) Next() bool {
+	if len(it.data) == 0 {
+		return false
+	}
+	_, t, c, err := readKind(it.data)
+	it.next = it.data[:t+c]
+	it.data = it.data[t+c:]
+	it.err = err
+	return true
+}
+
+// Value returns the current value
+func (it *listIterator) Value() []byte {
+	return it.next
+}
+
+func (it *listIterator) Err() error {
+	return it.err
+}

rlp/raw.go

@@ -0,0 +1,253 @@
+// Copyright 2015 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 (
+	"io"
+	"reflect"
+)
+
+// RawValue represents an encoded RLP value and can be used to delay
+// RLP decoding or to precompute an encoding. Note that the decoder does
+// not verify whether the content of RawValues is valid RLP.
+type RawValue []byte
+
+var rawValueType = reflect.TypeOf(RawValue{})
+
+// ListSize returns the encoded size of an RLP list with the given
+// content size.
+func ListSize(contentSize uint64) uint64 {
+	return uint64(headsize(contentSize)) + contentSize
+}
+
+// Split returns the content of first RLP value and any
+// bytes after the value as subslices of b.
+func Split(b []byte) (k Kind, content, rest []byte, err error) {
+	k, ts, cs, err := readKind(b)
+	if err != nil {
+		return 0, nil, b, err
+	}
+	return k, b[ts : ts+cs], b[ts+cs:], nil
+}
+
+// SplitString splits b into the content of an RLP string
+// and any remaining bytes after the string.
+func SplitString(b []byte) (content, rest []byte, err error) {
+	k, content, rest, err := Split(b)
+	if err != nil {
+		return nil, b, err
+	}
+	if k == List {
+		return nil, b, ErrExpectedString
+	}
+	return content, rest, nil
+}
+
+// SplitUint64 decodes an integer at the beginning of b.
+// It also returns the remaining data after the integer in 'rest'.
+func SplitUint64(b []byte) (x uint64, rest []byte, err error) {
+	content, rest, err := SplitString(b)
+	if err != nil {
+		return 0, b, err
+	}
+	switch {
+	case len(content) == 0:
+		return 0, rest, nil
+	case len(content) == 1:
+		if content[0] == 0 {
+			return 0, b, ErrCanonInt
+		}
+		return uint64(content[0]), rest, nil
+	case len(content) > 8:
+		return 0, b, errUintOverflow
+	default:
+		x, err = readSize(content, byte(len(content)))
+		if err != nil {
+			return 0, b, ErrCanonInt
+		}
+		return x, rest, nil
+	}
+}
+
+// SplitList splits b into the content of a list and any remaining
+// bytes after the list.
+func SplitList(b []byte) (content, rest []byte, err error) {
+	k, content, rest, err := Split(b)
+	if err != nil {
+		return nil, b, err
+	}
+	if k != List {
+		return nil, b, ErrExpectedList
+	}
+	return content, rest, nil
+}
+
+// CountValues counts the number of encoded values in b.
+func CountValues(b []byte) (int, error) {
+	i := 0
+	for ; len(b) > 0; i++ {
+		_, tagsize, size, err := readKind(b)
+		if err != nil {
+			return 0, err
+		}
+		b = b[tagsize+size:]
+	}
+	return i, nil
+}
+
+func readKind(buf []byte) (k Kind, tagsize, contentsize uint64, err error) {
+	if len(buf) == 0 {
+		return 0, 0, 0, io.ErrUnexpectedEOF
+	}
+	b := buf[0]
+	switch {
+	case b < 0x80:
+		k = Byte
+		tagsize = 0
+		contentsize = 1
+	case b < 0xB8:
+		k = String
+		tagsize = 1
+		contentsize = uint64(b - 0x80)
+		// Reject strings that should've been single bytes.
+		if contentsize == 1 && len(buf) > 1 && buf[1] < 128 {
+			return 0, 0, 0, ErrCanonSize
+		}
+	case b < 0xC0:
+		k = String
+		tagsize = uint64(b-0xB7) + 1
+		contentsize, err = readSize(buf[1:], b-0xB7)
+	case b < 0xF8:
+		k = List
+		tagsize = 1
+		contentsize = uint64(b - 0xC0)
+	default:
+		k = List
+		tagsize = uint64(b-0xF7) + 1
+		contentsize, err = readSize(buf[1:], b-0xF7)
+	}
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	// Reject values larger than the input slice.
+	if contentsize > uint64(len(buf))-tagsize {
+		return 0, 0, 0, ErrValueTooLarge
+	}
+	return k, tagsize, contentsize, err
+}
+
+func readSize(b []byte, slen byte) (uint64, error) {
+	if int(slen) > len(b) {
+		return 0, io.ErrUnexpectedEOF
+	}
+	var s uint64
+	switch slen {
+	case 1:
+		s = uint64(b[0])
+	case 2:
+		s = uint64(b[0])<<8 | uint64(b[1])
+	case 3:
+		s = uint64(b[0])<<16 | uint64(b[1])<<8 | uint64(b[2])
+	case 4:
+		s = uint64(b[0])<<24 | uint64(b[1])<<16 | uint64(b[2])<<8 | uint64(b[3])
+	case 5:
+		s = uint64(b[0])<<32 | uint64(b[1])<<24 | uint64(b[2])<<16 | uint64(b[3])<<8 | uint64(b[4])
+	case 6:
+		s = uint64(b[0])<<40 | uint64(b[1])<<32 | uint64(b[2])<<24 | uint64(b[3])<<16 | uint64(b[4])<<8 | uint64(b[5])
+	case 7:
+		s = uint64(b[0])<<48 | uint64(b[1])<<40 | uint64(b[2])<<32 | uint64(b[3])<<24 | uint64(b[4])<<16 | uint64(b[5])<<8 | uint64(b[6])
+	case 8:
+		s = uint64(b[0])<<56 | uint64(b[1])<<48 | uint64(b[2])<<40 | uint64(b[3])<<32 | uint64(b[4])<<24 | uint64(b[5])<<16 | uint64(b[6])<<8 | uint64(b[7])
+	}
+	// Reject sizes < 56 (shouldn't have separate size) and sizes with
+	// leading zero bytes.
+	if s < 56 || b[0] == 0 {
+		return 0, ErrCanonSize
+	}
+	return s, nil
+}
+
+// AppendUint64 appends the RLP encoding of i to b, and returns the resulting slice.
+func AppendUint64(b []byte, i uint64) []byte {
+	if i == 0 {
+		return append(b, 0x80)
+	} else if i < 128 {
+		return append(b, byte(i))
+	}
+	switch {
+	case i < (1 << 8):
+		return append(b, 0x81, byte(i))
+	case i < (1 << 16):
+		return append(b, 0x82,
+			byte(i>>8),
+			byte(i),
+		)
+	case i < (1 << 24):
+		return append(b, 0x83,
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+	case i < (1 << 32):
+		return append(b, 0x84,
+			byte(i>>24),
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+	case i < (1 << 40):
+		return append(b, 0x85,
+			byte(i>>32),
+			byte(i>>24),
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+
+	case i < (1 << 48):
+		return append(b, 0x86,
+			byte(i>>40),
+			byte(i>>32),
+			byte(i>>24),
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+	case i < (1 << 56):
+		return append(b, 0x87,
+			byte(i>>48),
+			byte(i>>40),
+			byte(i>>32),
+			byte(i>>24),
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+
+	default:
+		return append(b, 0x88,
+			byte(i>>56),
+			byte(i>>48),
+			byte(i>>40),
+			byte(i>>32),
+			byte(i>>24),
+			byte(i>>16),
+			byte(i>>8),
+			byte(i),
+		)
+	}
+}

rlp/safe.go

@@ -0,0 +1,27 @@
+// Copyright 2021 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/>.
+
+//go:build nacl || js || !cgo
+// +build nacl js !cgo
+
+package rlp
+
+import "reflect"
+
+// byteArrayBytes returns a slice of the byte array v.
+func byteArrayBytes(v reflect.Value) []byte {
+	return v.Slice(0, v.Len()).Bytes()
+}

rlp/typecache.go

@@ -0,0 +1,273 @@
+// 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 (
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+	"sync/atomic"
+)
+
+// typeinfo is an entry in the type cache.
+type typeinfo struct {
+	decoder    decoder
+	decoderErr error // error from makeDecoder
+	writer     writer
+	writerErr  error // error from makeWriter
+}
+
+// tags represents struct tags.
+type tags struct {
+	// rlp:"nil" controls whether empty input results in a nil pointer.
+	// nilKind is the kind of empty value allowed for the field.
+	nilKind Kind
+	nilOK   bool
+
+	// rlp:"optional" allows for a field to be missing in the input list.
+	// If this is set, all subsequent fields must also be optional.
+	optional bool
+
+	// rlp:"tail" controls whether this field swallows additional list elements. It can
+	// only be set for the last field, which must be of slice type.
+	tail bool
+
+	// rlp:"-" ignores fields.
+	ignored bool
+}
+
+// typekey is the key of a type in typeCache. It includes the struct tags because
+// they might generate a different decoder.
+type typekey struct {
+	reflect.Type
+	tags
+}
+
+type decoder func(*Stream, reflect.Value) error
+
+type writer func(reflect.Value, *encbuf) error
+
+var theTC = newTypeCache()
+
+type typeCache struct {
+	cur atomic.Value
+
+	// This lock synchronizes writers.
+	mu   sync.Mutex
+	next map[typekey]*typeinfo
+}
+
+func newTypeCache() *typeCache {
+	c := new(typeCache)
+	c.cur.Store(make(map[typekey]*typeinfo))
+	return c
+}
+
+func cachedDecoder(typ reflect.Type) (decoder, error) {
+	info := theTC.info(typ)
+	return info.decoder, info.decoderErr
+}
+
+func cachedWriter(typ reflect.Type) (writer, error) {
+	info := theTC.info(typ)
+	return info.writer, info.writerErr
+}
+
+func (c *typeCache) info(typ reflect.Type) *typeinfo {
+	key := typekey{Type: typ}
+	if info := c.cur.Load().(map[typekey]*typeinfo)[key]; info != nil {
+		return info
+	}
+
+	// Not in the cache, need to generate info for this type.
+	return c.generate(typ, tags{})
+}
+
+func (c *typeCache) generate(typ reflect.Type, tags tags) *typeinfo {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	cur := c.cur.Load().(map[typekey]*typeinfo)
+	if info := cur[typekey{typ, tags}]; info != nil {
+		return info
+	}
+
+	// Copy cur to next.
+	c.next = make(map[typekey]*typeinfo, len(cur)+1)
+	for k, v := range cur {
+		c.next[k] = v
+	}
+
+	// Generate.
+	info := c.infoWhileGenerating(typ, tags)
+
+	// next -> cur
+	c.cur.Store(c.next)
+	c.next = nil
+	return info
+}
+
+func (c *typeCache) infoWhileGenerating(typ reflect.Type, tags tags) *typeinfo {
+	key := typekey{typ, tags}
+	if info := c.next[key]; info != nil {
+		return info
+	}
+	// Put a dummy value into the cache before generating.
+	// If the generator tries to lookup itself, it will get
+	// the dummy value and won't call itself recursively.
+	info := new(typeinfo)
+	c.next[key] = info
+	info.generate(typ, tags)
+	return info
+}
+
+type field struct {
+	index    int
+	info     *typeinfo
+	optional bool
+}
+
+// structFields resolves the typeinfo of all public fields in a struct type.
+func structFields(typ reflect.Type) (fields []field, err error) {
+	var (
+		lastPublic  = lastPublicField(typ)
+		anyOptional = false
+	)
+	for i := 0; i < typ.NumField(); i++ {
+		if f := typ.Field(i); f.PkgPath == "" { // exported
+			tags, err := parseStructTag(typ, i, lastPublic)
+			if err != nil {
+				return nil, err
+			}
+
+			// Skip rlp:"-" fields.
+			if tags.ignored {
+				continue
+			}
+			// If any field has the "optional" tag, subsequent fields must also have it.
+			if tags.optional || tags.tail {
+				anyOptional = true
+			} else if anyOptional {
+				return nil, fmt.Errorf(`rlp: struct field %v.%s needs "optional" tag`, typ, f.Name)
+			}
+			info := theTC.infoWhileGenerating(f.Type, tags)
+			fields = append(fields, field{i, info, tags.optional})
+		}
+	}
+	return fields, nil
+}
+
+type structFieldError struct {
+	typ   reflect.Type
+	field int
+	err   error
+}
+
+func (e structFieldError) Error() string {
+	return fmt.Sprintf("%v (struct field %v.%s)", e.err, e.typ, e.typ.Field(e.field).Name)
+}
+
+type structTagError struct {
+	typ             reflect.Type
+	field, tag, err string
+}
+
+func (e structTagError) Error() string {
+	return fmt.Sprintf("rlp: invalid struct tag %q for %v.%s (%s)", e.tag, e.typ, e.field, e.err)
+}
+
+func parseStructTag(typ reflect.Type, fi, lastPublic int) (tags, error) {
+	f := typ.Field(fi)
+	var ts tags
+	for _, t := range strings.Split(f.Tag.Get("rlp"), ",") {
+		switch t = strings.TrimSpace(t); t {
+		case "":
+		case "-":
+			ts.ignored = true
+		case "nil", "nilString", "nilList":
+			ts.nilOK = true
+			if f.Type.Kind() != reflect.Ptr {
+				return ts, structTagError{typ, f.Name, t, "field is not a pointer"}
+			}
+			switch t {
+			case "nil":
+				ts.nilKind = defaultNilKind(f.Type.Elem())
+			case "nilString":
+				ts.nilKind = String
+			case "nilList":
+				ts.nilKind = List
+			}
+		case "optional":
+			ts.optional = true
+			if ts.tail {
+				return ts, structTagError{typ, f.Name, t, `also has "tail" tag`}
+			}
+		case "tail":
+			ts.tail = true
+			if fi != lastPublic {
+				return ts, structTagError{typ, f.Name, t, "must be on last field"}
+			}
+			if ts.optional {
+				return ts, structTagError{typ, f.Name, t, `also has "optional" tag`}
+			}
+			if f.Type.Kind() != reflect.Slice {
+				return ts, structTagError{typ, f.Name, t, "field type is not slice"}
+			}
+		default:
+			return ts, fmt.Errorf("rlp: unknown struct tag %q on %v.%s", t, typ, f.Name)
+		}
+	}
+	return ts, nil
+}
+
+func lastPublicField(typ reflect.Type) int {
+	last := 0
+	for i := 0; i < typ.NumField(); i++ {
+		if typ.Field(i).PkgPath == "" {
+			last = i
+		}
+	}
+	return last
+}
+
+func (i *typeinfo) generate(typ reflect.Type, tags tags) {
+	i.decoder, i.decoderErr = makeDecoder(typ, tags)
+	i.writer, i.writerErr = makeWriter(typ, tags)
+}
+
+// defaultNilKind determines whether a nil pointer to typ encodes/decodes
+// as an empty string or empty list.
+func defaultNilKind(typ reflect.Type) Kind {
+	k := typ.Kind()
+	if isUint(k) || k == reflect.String || k == reflect.Bool || isByteArray(typ) {
+		return String
+	}
+	return List
+}
+
+func isUint(k reflect.Kind) bool {
+	return k >= reflect.Uint && k <= reflect.Uintptr
+}
+
+func isByte(typ reflect.Type) bool {
+	return typ.Kind() == reflect.Uint8 && !typ.Implements(encoderInterface)
+}
+
+func isByteArray(typ reflect.Type) bool {
+	return (typ.Kind() == reflect.Slice || typ.Kind() == reflect.Array) && isByte(typ.Elem())
+}

rlp/unsafe.go

@@ -0,0 +1,36 @@
+// Copyright 2021 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/>.
+
+//go:build !nacl && !js && cgo
+// +build !nacl,!js,cgo
+
+package rlp
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// byteArrayBytes returns a slice of the byte array v.
+func byteArrayBytes(v reflect.Value) []byte {
+	len := v.Len()
+	var s []byte
+	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&s))
+	hdr.Data = v.UnsafeAddr()
+	hdr.Cap = len
+	hdr.Len = len
+	return s
+}