plugeth/rlp/encode.go
Felix Lange 700df1442d
rlp: add support for optional struct fields (#22832)
This adds support for a new struct tag "optional". Using this tag, structs used
for RLP encoding/decoding can be extended in a backwards-compatible way,
by adding new fields at the end.
2021-05-07 14:37:13 +02:00

699 lines
18 KiB
Go

// 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
bufvalue reflect.Value // used in writeByteArrayCopy
}
// encbufs are pooled.
var encbufPool = sync.Pool{
New: func() interface{} {
var bytes []byte
return &encbuf{bufvalue: reflect.ValueOf(&bytes).Elem()}
},
}
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
}
var byteType = reflect.TypeOf(byte(0))
func makeByteArrayWriter(typ reflect.Type) writer {
length := typ.Len()
if length == 0 {
return writeLengthZeroByteArray
} else if length == 1 {
return writeLengthOneByteArray
}
if typ.Elem() != byteType {
return writeNamedByteArray
}
return func(val reflect.Value, w *encbuf) error {
writeByteArrayCopy(length, val, w)
return nil
}
}
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
}
// writeByteArrayCopy encodes byte arrays using reflect.Copy. This is
// the fast path for [N]byte where N > 1.
func writeByteArrayCopy(length int, val reflect.Value, w *encbuf) {
w.encodeStringHeader(length)
offset := len(w.str)
w.str = append(w.str, make([]byte, length)...)
w.bufvalue.SetBytes(w.str[offset:])
reflect.Copy(w.bufvalue, val)
}
// writeNamedByteArray encodes byte arrays with named element type.
// This exists because reflect.Copy can't be used with such types.
func writeNamedByteArray(val reflect.Value, w *encbuf) error {
if !val.CanAddr() {
// Slice requires the value to be addressable.
// Make it addressable by copying.
copy := reflect.New(val.Type()).Elem()
copy.Set(val)
val = copy
}
size := val.Len()
slice := val.Slice(0, size).Bytes()
w.encodeString(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 := cachedTypeInfo1(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}
}
}
var writer writer
firstOptionalField := firstOptionalField(fields)
if firstOptionalField == len(fields) {
// This is the writer function for structs without any optional fields.
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
}
} else {
// If there are any "optional" fields, the writer needs to perform additional
// checks to determine the output list length.
writer = func(val reflect.Value, w *encbuf) error {
lastField := len(fields) - 1
for ; lastField >= firstOptionalField; lastField-- {
if !val.Field(fields[lastField].index).IsZero() {
break
}
}
lh := w.list()
for i := 0; i <= lastField; i++ {
if err := fields[i].info.writer(val.Field(fields[i].index), w); err != nil {
return err
}
}
w.listEnd(lh)
return nil
}
}
return writer, nil
}
func makePtrWriter(typ reflect.Type, ts tags) (writer, error) {
etypeinfo := cachedTypeInfo1(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
}
}
}