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rlp.go
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rlp.go
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package ethtypes
import (
"bytes"
"encoding/binary"
"fmt"
"golang.org/x/xerrors"
)
// maxListElements restricts the amount of RLP list elements we'll read.
// The ETH API only ever reads EIP-1559 transactions, which are bounded by
// 12 elements exactly, so we play it safe and set exactly that limit here.
const maxListElements = 12
func EncodeRLP(val interface{}) ([]byte, error) {
return encodeRLP(val)
}
func encodeRLPListItems(list []interface{}) (result []byte, err error) {
res := []byte{}
for _, elem := range list {
encoded, err := encodeRLP(elem)
if err != nil {
return nil, err
}
res = append(res, encoded...)
}
return res, nil
}
func encodeLength(length int) (lenInBytes []byte, err error) {
if length == 0 {
return nil, fmt.Errorf("cannot encode length: length should be larger than 0")
}
buf := new(bytes.Buffer)
err = binary.Write(buf, binary.BigEndian, int64(length))
if err != nil {
return nil, err
}
firstNonZeroIndex := len(buf.Bytes()) - 1
for i, b := range buf.Bytes() {
if b != 0 {
firstNonZeroIndex = i
break
}
}
res := buf.Bytes()[firstNonZeroIndex:]
return res, nil
}
func encodeRLP(val interface{}) ([]byte, error) {
switch data := val.(type) {
case []byte:
if len(data) == 1 && data[0] <= 0x7f {
return data, nil
} else if len(data) <= 55 {
prefix := byte(0x80 + len(data))
return append([]byte{prefix}, data...), nil
} else {
lenInBytes, err := encodeLength(len(data))
if err != nil {
return nil, err
}
prefix := byte(0xb7 + len(lenInBytes))
return append(
[]byte{prefix},
append(lenInBytes, data...)...,
), nil
}
case []interface{}:
encodedList, err := encodeRLPListItems(data)
if err != nil {
return nil, err
}
if len(encodedList) <= 55 {
prefix := byte(0xc0 + len(encodedList))
return append(
[]byte{prefix},
encodedList...,
), nil
}
lenInBytes, err := encodeLength(len(encodedList))
if err != nil {
return nil, err
}
prefix := byte(0xf7 + len(lenInBytes))
return append(
[]byte{prefix},
append(lenInBytes, encodedList...)...,
), nil
default:
return nil, fmt.Errorf("input data should either be a list or a byte array")
}
}
func DecodeRLP(data []byte) (interface{}, error) {
res, consumed, err := decodeRLP(data)
if err != nil {
return nil, err
}
if consumed != len(data) {
return nil, xerrors.Errorf("invalid rlp data: length %d, consumed %d", len(data), consumed)
}
return res, nil
}
func decodeRLP(data []byte) (res interface{}, consumed int, err error) {
if len(data) == 0 {
return data, 0, xerrors.Errorf("invalid rlp data: data cannot be empty")
}
if data[0] >= 0xf8 {
listLenInBytes := int(data[0]) - 0xf7
listLen, err := decodeLength(data[1:], listLenInBytes)
if err != nil {
return nil, 0, err
}
if 1+listLenInBytes+listLen > len(data) {
return nil, 0, xerrors.Errorf("invalid rlp data: out of bound while parsing list")
}
result, err := decodeListElems(data[1+listLenInBytes:], listLen)
return result, 1 + listLenInBytes + listLen, err
} else if data[0] >= 0xc0 {
length := int(data[0]) - 0xc0
result, err := decodeListElems(data[1:], length)
return result, 1 + length, err
} else if data[0] >= 0xb8 {
strLenInBytes := int(data[0]) - 0xb7
strLen, err := decodeLength(data[1:], strLenInBytes)
if err != nil {
return nil, 0, err
}
totalLen := 1 + strLenInBytes + strLen
if totalLen > len(data) {
return nil, 0, xerrors.Errorf("invalid rlp data: out of bound while parsing string")
}
return data[1+strLenInBytes : totalLen], totalLen, nil
} else if data[0] >= 0x80 {
length := int(data[0]) - 0x80
if 1+length > len(data) {
return nil, 0, xerrors.Errorf("invalid rlp data: out of bound while parsing string")
}
return data[1 : 1+length], 1 + length, nil
}
return []byte{data[0]}, 1, nil
}
func decodeLength(data []byte, lenInBytes int) (length int, err error) {
if lenInBytes > len(data) || lenInBytes > 8 {
return 0, xerrors.Errorf("invalid rlp data: out of bound while parsing list length")
}
var decodedLength int64
r := bytes.NewReader(append(make([]byte, 8-lenInBytes), data[:lenInBytes]...))
if err := binary.Read(r, binary.BigEndian, &decodedLength); err != nil {
return 0, xerrors.Errorf("invalid rlp data: cannot parse string length: %w", err)
}
if decodedLength < 0 {
return 0, xerrors.Errorf("invalid rlp data: negative string length")
}
if lenInBytes+int(decodedLength) > len(data) {
return 0, xerrors.Errorf("invalid rlp data: out of bound while parsing list")
}
return int(decodedLength), nil
}
func decodeListElems(data []byte, length int) (res []interface{}, err error) {
totalConsumed := 0
result := []interface{}{}
for i := 0; totalConsumed < length && i < maxListElements; i++ {
elem, consumed, err := decodeRLP(data[totalConsumed:])
if err != nil {
return nil, xerrors.Errorf("invalid rlp data: cannot decode list element: %w", err)
}
totalConsumed += consumed
result = append(result, elem)
}
if totalConsumed != length {
return nil, xerrors.Errorf("invalid rlp data: incorrect list length")
}
return result, nil
}