package rlp
import (
"fmt"
"io"
"math/big"
"reflect"
)
// TODO: put encbufs in a sync.Pool.
// Doing that requires zeroing the buffers after use.
// encReader will need to drop it's buffer when done.
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.
//
// Encode uses the following type-dependent encoding rules:
//
// If the type implements the Encoder interface, Encode calls
// EncodeRLP. This is true even for nil pointers, please see the
// documentation for Encoder.
//
// To encode a pointer, the value being pointed to is encoded. For nil
// pointers, Encode will encode the zero value of the type. A nil
// pointer to a struct type always encodes as an empty RLP list.
//
// 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. Encode also supports *big.Int.
//
// An interface value encodes as the value contained in the interface.
//
// Boolean values are not supported, nor are signed integers, floating
// point numbers, maps, channels and functions.
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 := newencbuf()
if err := eb.encode(val); err != nil {
return err
}
return eb.toWriter(w)
}
// EncodeBytes returns the RLP encoding of val.
// Please see the documentation of Encode for the encoding rules.
func EncodeToBytes(val interface{}) ([]byte, error) {
eb := newencbuf()
if err := eb.encode(val); err != nil {
return nil, err
}
return eb.toBytes(), nil
}
// EncodeReader 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 := newencbuf()
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 {
if head.size < 56 {
buf[0] = 0xC0 + byte(head.size)
return buf[:1]
} else {
sizesize := putint(buf[1:], uint64(head.size))
buf[0] = 0xF7 + byte(sizesize)
return buf[:sizesize+1]
}
}
func newencbuf() *encbuf {
return &encbuf{sizebuf: make([]byte, 9)}
}
// 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)
ti, err := cachedTypeInfo(rval.Type())
if err != nil {
return err
}
return ti.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) {
w.encodeStringHeader(len(b))
w.str = append(w.str, b...)
}
func (w *encbuf) list() *listhead {
lh := &listhead{offset: len(w.str), size: w.lhsize}
w.lheads = append(w.lheads, lh)
return lh
}
func (w *encbuf) listEnd(lh *listhead) {
lh.size = w.size() - lh.offset - lh.size
if lh.size < 56 {
w.lhsize += 1 // 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 {
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
}
panic("not reached")
}
// next returns the next piece of data to be read.
// it returns nil at EOF.
func (r *encReader) next() []byte {
switch {
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
} else {
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()
emptyInterface = reflect.TypeOf(new(interface{})).Elem()
big0 = big.NewInt(0)
)
// makeWriter creates a writer function for the given type.
func makeWriter(typ reflect.Type) (writer, error) {
kind := typ.Kind()
switch {
case typ.Implements(encoderInterface):
return writeEncoder, nil
case kind != reflect.Ptr && reflect.PtrTo(typ).Implements(encoderInterface):
return writeEncoderNoPtr, nil
case typ == emptyInterface:
return writeInterface, nil
case typ.AssignableTo(reflect.PtrTo(bigInt)):
return writeBigIntPtr, nil
case typ.AssignableTo(bigInt):
return writeBigIntNoPtr, nil
case isUint(kind):
return writeUint, nil
case kind == reflect.String:
return writeString, nil
case kind == reflect.Slice && typ.Elem().Kind() == reflect.Uint8 && !typ.Elem().Implements(encoderInterface):
return writeBytes, nil
case kind == reflect.Slice || kind == reflect.Array:
return makeSliceWriter(typ)
case kind == reflect.Struct:
return makeStructWriter(typ)
case kind == reflect.Ptr:
return makePtrWriter(typ)
default:
return nil, fmt.Errorf("rlp: type %v is not RLP-serializable", typ)
}
}
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 writeBigIntPtr(val reflect.Value, w *encbuf) error {
return writeBigInt(val.Interface().(*big.Int), 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 if bits := i.BitLen(); bits < 8 {
// fits single byte
w.str = append(w.str, byte(i.Uint64()))
} else {
w.encodeString(i.Bytes())
}
return nil
}
func writeBytes(val reflect.Value, w *encbuf) error {
w.encodeString(val.Bytes())
return nil
}
func writeString(val reflect.Value, w *encbuf) error {
s := val.String()
w.encodeStringHeader(len(s))
w.str = append(w.str, s...)
return nil
}
func writeEncoder(val reflect.Value, w *encbuf) error {
return val.Interface().(Encoder).EncodeRLP(w)
}
// writeEncoderNoPtr handles non-pointer values that implement Encoder
// with a pointer receiver.
func writeEncoderNoPtr(val reflect.Value, w *encbuf) error {
if !val.CanAddr() {
// We can't get the address. It would be possible make the
// value addressable by creating a shallow copy, but this
// creates other problems so we're not doing it (yet).
//
// package json simply doesn't call MarshalJSON for cases like
// this, 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: game over: unadressable value of type %v, EncodeRLP is pointer method", val.Type())
}
return val.Addr().Interface().(Encoder).EncodeRLP(w)
}
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()
ti, err := cachedTypeInfo(eval.Type())
if err != nil {
return err
}
return ti.writer(eval, w)
}
func makeSliceWriter(typ reflect.Type) (writer, error) {
etypeinfo, err := cachedTypeInfo1(typ.Elem())
if err != nil {
return nil, err
}
writer := func(val reflect.Value, w *encbuf) error {
lh := w.list()
vlen := val.Len()
for i := 0; i < vlen; i++ {
if err := etypeinfo.writer(val.Index(i), w); err != nil {
return err
}
}
w.listEnd(lh)
return nil
}
return writer, nil
}
func makeStructWriter(typ reflect.Type) (writer, error) {
fields, err := structFields(typ)
if err != nil {
return nil, err
}
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) (writer, error) {
etypeinfo, err := cachedTypeInfo1(typ.Elem())
if err != nil {
return nil, err
}
zero := reflect.Zero(typ.Elem())
kind := typ.Elem().Kind()
writer := func(val reflect.Value, w *encbuf) error {
switch {
case !val.IsNil():
return etypeinfo.writer(val.Elem(), w)
case kind == reflect.Struct:
// encoding the zero value of a struct could trigger
// infinite recursion, avoid that.
w.listEnd(w.list())
return nil
default:
return etypeinfo.writer(zero, w)
}
}
return writer, err
}
// putint writes i to the beginning of b in with 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
}
}
panic("not reached")
}
