Official Go implementation of the Ethereum protocol
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go-ethereum/rlp/encode.go

612 lines
15 KiB

// 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.
//
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
// 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.
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
// 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 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 []byte // 9-byte auxiliary buffer for uint encoding
}
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)
10 years ago
return 1
}
sizesize := putint(buf[1:], size)
buf[0] = largetag + byte(sizesize)
return sizesize + 1
10 years ago
}
// encbufs are pooled.
var encbufPool = sync.Pool{
New: func() interface{} { return &encbuf{sizebuf: make([]byte, 9)} },
}
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 {
// TODO: encode to w.str directly
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...)
}
}
// 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()
big0 = big.NewInt(0)
)
// 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
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
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 writeByteArray, nil
case kind == reflect.Slice || kind == reflect.Array:
return makeSliceWriter(typ, ts)
case kind == reflect.Struct:
return makeStructWriter(typ)
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
case kind == reflect.Interface:
return writeInterface, nil
default:
return nil, fmt.Errorf("rlp: type %v is not RLP-serializable", typ)
}
}
func isByte(typ reflect.Type) bool {
return typ.Kind() == reflect.Uint8 && !typ.Implements(encoderInterface)
}
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 {
i := val.Uint()
if i == 0 {
w.str = append(w.str, 0x80)
} else if i < 128 {
// fits single byte
w.str = append(w.str, byte(i))
} else {
// TODO: encode int to w.str directly
s := putint(w.sizebuf[1:], i)
w.sizebuf[0] = 0x80 + byte(s)
w.str = append(w.str, w.sizebuf[:s+1]...)
}
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)
}
func writeBigInt(i *big.Int, w *encbuf) error {
if cmp := i.Cmp(big0); cmp == -1 {
return fmt.Errorf("rlp: cannot encode negative *big.Int")
} else if cmp == 0 {
w.str = append(w.str, 0x80)
} else {
w.encodeString(i.Bytes())
}
return nil
}
func writeBytes(val reflect.Value, w *encbuf) error {
w.encodeString(val.Bytes())
return nil
}
func writeByteArray(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
}
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
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
}
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
func makePtrWriter(typ reflect.Type, ts tags) (writer, error) {
etypeinfo := cachedTypeInfo1(typ.Elem(), tags{})
if etypeinfo.writerErr != nil {
return nil, etypeinfo.writerErr
}
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
// 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() {
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
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
}
rlp: improve nil pointer handling (#20064) * rlp: improve nil pointer handling In both encoder and decoder, the rules for encoding nil pointers were a bit hard to understand, and didn't leave much choice. Since RLP allows two empty values (empty list, empty string), any protocol built on RLP must choose either of these values to represent the null value in a certain context. This change adds choice in the form of two new struct tags, "nilString" and "nilList". These can be used to specify how a nil pointer value is encoded. The "nil" tag still exists, but its implementation is now explicit and defines exactly how nil pointers are handled in a single place. Another important change in this commit is how nil pointers and the Encoder interface interact. The EncodeRLP method was previously called even on nil values, which was supposed to give users a choice of how their value would be handled when nil. It turns out this is a stupid idea. If you create a network protocol containing an object defined in another package, it's better to be able to say that the object should be a list or string when nil in the definition of the protocol message rather than defining the encoding of nil on the object itself. As of this commit, the encoding rules for pointers now take precedence over the Encoder interface rule. I think the "nil" tag will work fine for most cases. For special kinds of objects which are a struct in Go but strings in RLP, code using the object can specify the desired encoding of nil using the "nilString" and "nilList" tags. * rlp: propagate struct field type errors If a struct contained fields of undecodable type, the encoder and decoder would panic instead of returning an error. Fix this by propagating type errors in makeStruct{Writer,Decoder} and add a test.
5 years ago
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
}
}
}