Official Go implementation of the Ethereum protocol
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go-ethereum/accounts/abi/unpack.go

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// Copyright 2017 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 abi
import (
"encoding/binary"
"errors"
"fmt"
"math"
"math/big"
"reflect"
"github.com/ethereum/go-ethereum/common"
)
var (
// MaxUint256 is the maximum value that can be represented by a uint256.
MaxUint256 = new(big.Int).Sub(new(big.Int).Lsh(common.Big1, 256), common.Big1)
// MaxInt256 is the maximum value that can be represented by a int256.
MaxInt256 = new(big.Int).Sub(new(big.Int).Lsh(common.Big1, 255), common.Big1)
)
// ReadInteger reads the integer based on its kind and returns the appropriate value.
func ReadInteger(typ Type, b []byte) (interface{}, error) {
ret := new(big.Int).SetBytes(b)
if typ.T == UintTy {
u64, isu64 := ret.Uint64(), ret.IsUint64()
switch typ.Size {
case 8:
if !isu64 || u64 > math.MaxUint8 {
return nil, errBadUint8
}
return byte(u64), nil
case 16:
if !isu64 || u64 > math.MaxUint16 {
return nil, errBadUint16
}
return uint16(u64), nil
case 32:
if !isu64 || u64 > math.MaxUint32 {
return nil, errBadUint32
}
return uint32(u64), nil
case 64:
if !isu64 {
return nil, errBadUint64
}
return u64, nil
default:
// the only case left for unsigned integer is uint256.
return ret, nil
}
}
// big.SetBytes can't tell if a number is negative or positive in itself.
// On EVM, if the returned number > max int256, it is negative.
// A number is > max int256 if the bit at position 255 is set.
if ret.Bit(255) == 1 {
ret.Add(MaxUint256, new(big.Int).Neg(ret))
ret.Add(ret, common.Big1)
ret.Neg(ret)
}
i64, isi64 := ret.Int64(), ret.IsInt64()
switch typ.Size {
case 8:
if !isi64 || i64 < math.MinInt8 || i64 > math.MaxInt8 {
return nil, errBadInt8
}
return int8(i64), nil
case 16:
if !isi64 || i64 < math.MinInt16 || i64 > math.MaxInt16 {
return nil, errBadInt16
}
return int16(i64), nil
case 32:
if !isi64 || i64 < math.MinInt32 || i64 > math.MaxInt32 {
return nil, errBadInt32
}
return int32(i64), nil
case 64:
if !isi64 {
return nil, errBadInt64
}
return i64, nil
default:
// the only case left for integer is int256
return ret, nil
}
}
// readBool reads a bool.
func readBool(word []byte) (bool, error) {
for _, b := range word[:31] {
if b != 0 {
return false, errBadBool
}
}
switch word[31] {
case 0:
return false, nil
case 1:
return true, nil
default:
return false, errBadBool
}
}
// A function type is simply the address with the function selection signature at the end.
//
// readFunctionType enforces that standard by always presenting it as a 24-array (address + sig = 24 bytes)
func readFunctionType(t Type, word []byte) (funcTy [24]byte, err error) {
if t.T != FunctionTy {
return [24]byte{}, errors.New("abi: invalid type in call to make function type byte array")
}
if garbage := binary.BigEndian.Uint64(word[24:32]); garbage != 0 {
err = fmt.Errorf("abi: got improperly encoded function type, got %v", word)
} else {
copy(funcTy[:], word[0:24])
}
return
}
// ReadFixedBytes uses reflection to create a fixed array to be read from.
func ReadFixedBytes(t Type, word []byte) (interface{}, error) {
if t.T != FixedBytesTy {
return nil, errors.New("abi: invalid type in call to make fixed byte array")
}
// convert
array := reflect.New(t.GetType()).Elem()
reflect.Copy(array, reflect.ValueOf(word[0:t.Size]))
return array.Interface(), nil
}
// forEachUnpack iteratively unpack elements.
func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error) {
if size < 0 {
return nil, fmt.Errorf("cannot marshal input to array, size is negative (%d)", size)
}
if start+32*size > len(output) {
return nil, fmt.Errorf("abi: cannot marshal into go array: offset %d would go over slice boundary (len=%d)", len(output), start+32*size)
}
// this value will become our slice or our array, depending on the type
var refSlice reflect.Value
if t.T == SliceTy {
// declare our slice
refSlice = reflect.MakeSlice(t.GetType(), size, size)
} else if t.T == ArrayTy {
// declare our array
refSlice = reflect.New(t.GetType()).Elem()
} else {
return nil, errors.New("abi: invalid type in array/slice unpacking stage")
}
// Arrays have packed elements, resulting in longer unpack steps.
// Slices have just 32 bytes per element (pointing to the contents).
elemSize := getTypeSize(*t.Elem)
for i, j := start, 0; j < size; i, j = i+elemSize, j+1 {
inter, err := toGoType(i, *t.Elem, output)
if err != nil {
return nil, err
}
// append the item to our reflect slice
refSlice.Index(j).Set(reflect.ValueOf(inter))
}
// return the interface
return refSlice.Interface(), nil
}
func forTupleUnpack(t Type, output []byte) (interface{}, error) {
retval := reflect.New(t.GetType()).Elem()
virtualArgs := 0
for index, elem := range t.TupleElems {
marshalledValue, err := toGoType((index+virtualArgs)*32, *elem, output)
if err != nil {
return nil, err
}
if elem.T == ArrayTy && !isDynamicType(*elem) {
// If we have a static array, like [3]uint256, these are coded as
// just like uint256,uint256,uint256.
// This means that we need to add two 'virtual' arguments when
// we count the index from now on.
//
// Array values nested multiple levels deep are also encoded inline:
// [2][3]uint256: uint256,uint256,uint256,uint256,uint256,uint256
//
// Calculate the full array size to get the correct offset for the next argument.
// Decrement it by 1, as the normal index increment is still applied.
virtualArgs += getTypeSize(*elem)/32 - 1
} else if elem.T == TupleTy && !isDynamicType(*elem) {
// If we have a static tuple, like (uint256, bool, uint256), these are
// coded as just like uint256,bool,uint256
virtualArgs += getTypeSize(*elem)/32 - 1
}
retval.Field(index).Set(reflect.ValueOf(marshalledValue))
}
return retval.Interface(), nil
}
// toGoType parses the output bytes and recursively assigns the value of these bytes
// into a go type with accordance with the ABI spec.
func toGoType(index int, t Type, output []byte) (interface{}, error) {
if index+32 > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), index+32)
}
var (
returnOutput []byte
begin, length int
err error
)
// if we require a length prefix, find the beginning word and size returned.
if t.requiresLengthPrefix() {
begin, length, err = lengthPrefixPointsTo(index, output)
if err != nil {
return nil, err
}
} else {
returnOutput = output[index : index+32]
}
switch t.T {
case TupleTy:
if isDynamicType(t) {
begin, err := tuplePointsTo(index, output)
if err != nil {
return nil, err
}
return forTupleUnpack(t, output[begin:])
}
return forTupleUnpack(t, output[index:])
case SliceTy:
return forEachUnpack(t, output[begin:], 0, length)
case ArrayTy:
if isDynamicType(*t.Elem) {
offset := binary.BigEndian.Uint64(returnOutput[len(returnOutput)-8:])
if offset > uint64(len(output)) {
return nil, fmt.Errorf("abi: toGoType offset greater than output length: offset: %d, len(output): %d", offset, len(output))
}
return forEachUnpack(t, output[offset:], 0, t.Size)
}
return forEachUnpack(t, output[index:], 0, t.Size)
case StringTy: // variable arrays are written at the end of the return bytes
return string(output[begin : begin+length]), nil
case IntTy, UintTy:
return ReadInteger(t, returnOutput)
case BoolTy:
return readBool(returnOutput)
case AddressTy:
return common.BytesToAddress(returnOutput), nil
case HashTy:
return common.BytesToHash(returnOutput), nil
case BytesTy:
return output[begin : begin+length], nil
case FixedBytesTy:
return ReadFixedBytes(t, returnOutput)
case FunctionTy:
return readFunctionType(t, returnOutput)
default:
return nil, fmt.Errorf("abi: unknown type %v", t.T)
}
}
// lengthPrefixPointsTo interprets a 32 byte slice as an offset and then determines which indices to look to decode the type.
func lengthPrefixPointsTo(index int, output []byte) (start int, length int, err error) {
bigOffsetEnd := new(big.Int).SetBytes(output[index : index+32])
bigOffsetEnd.Add(bigOffsetEnd, common.Big32)
outputLength := big.NewInt(int64(len(output)))
if bigOffsetEnd.Cmp(outputLength) > 0 {
return 0, 0, fmt.Errorf("abi: cannot marshal in to go slice: offset %v would go over slice boundary (len=%v)", bigOffsetEnd, outputLength)
}
if bigOffsetEnd.BitLen() > 63 {
return 0, 0, fmt.Errorf("abi offset larger than int64: %v", bigOffsetEnd)
}
offsetEnd := int(bigOffsetEnd.Uint64())
lengthBig := new(big.Int).SetBytes(output[offsetEnd-32 : offsetEnd])
totalSize := new(big.Int).Add(bigOffsetEnd, lengthBig)
if totalSize.BitLen() > 63 {
return 0, 0, fmt.Errorf("abi: length larger than int64: %v", totalSize)
}
if totalSize.Cmp(outputLength) > 0 {
return 0, 0, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %v require %v", outputLength, totalSize)
}
start = int(bigOffsetEnd.Uint64())
length = int(lengthBig.Uint64())
return
}
// tuplePointsTo resolves the location reference for dynamic tuple.
func tuplePointsTo(index int, output []byte) (start int, err error) {
offset := new(big.Int).SetBytes(output[index : index+32])
outputLen := big.NewInt(int64(len(output)))
if offset.Cmp(outputLen) > 0 {
return 0, fmt.Errorf("abi: cannot marshal in to go slice: offset %v would go over slice boundary (len=%v)", offset, outputLen)
}
if offset.BitLen() > 63 {
return 0, fmt.Errorf("abi offset larger than int64: %v", offset)
}
return int(offset.Uint64()), nil
}