// 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"
"fmt"
"math/big"
"reflect"
"github.com/ethereum/go-ethereum/common"
)
var (
maxUint256 = big.NewInt(0).Add(
big.NewInt(0).Exp(big.NewInt(2), big.NewInt(256), nil),
big.NewInt(-1))
maxInt256 = big.NewInt(0).Add(
big.NewInt(0).Exp(big.NewInt(2), big.NewInt(255), nil),
big.NewInt(-1))
)
// reads the integer based on its kind
func readInteger(typ byte, kind reflect.Kind, b []byte) interface{} {
switch kind {
case reflect.Uint8:
return b[len(b)-1]
case reflect.Uint16:
return binary.BigEndian.Uint16(b[len(b)-2:])
case reflect.Uint32:
return binary.BigEndian.Uint32(b[len(b)-4:])
case reflect.Uint64:
return binary.BigEndian.Uint64(b[len(b)-8:])
case reflect.Int8:
return int8(b[len(b)-1])
case reflect.Int16:
return int16(binary.BigEndian.Uint16(b[len(b)-2:]))
case reflect.Int32:
return int32(binary.BigEndian.Uint32(b[len(b)-4:]))
case reflect.Int64:
return int64(binary.BigEndian.Uint64(b[len(b)-8:]))
default:
// the only case lefts for integer is int256/uint256.
// big.SetBytes can't tell if a number is negative, positive on itself.
// On EVM, if the returned number > max int256, it is negative.
ret := new(big.Int).SetBytes(b)
if typ == UintTy {
return ret
}
if ret.Cmp(maxInt256) > 0 {
ret.Add(maxUint256, big.NewInt(0).Neg(ret))
ret.Add(ret, big.NewInt(1))
ret.Neg(ret)
}
return ret
}
}
// 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.
// This 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{}, fmt.Errorf("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
}
// through reflection, creates a fixed array to be read from
func readFixedBytes(t Type, word []byte) (interface{}, error) {
if t.T != FixedBytesTy {
return nil, fmt.Errorf("abi: invalid type in call to make fixed byte array")
}
// convert
array := reflect.New(t.Type).Elem()
reflect.Copy(array, reflect.ValueOf(word[0:t.Size]))
return array.Interface(), nil
}
func getFullElemSize(elem *Type) int {
//all other should be counted as 32 (slices have pointers to respective elements)
size := 32
//arrays wrap it, each element being the same size
for elem.T == ArrayTy {
size *= elem.Size
elem = elem.Elem
}
return size
}
// 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 in to 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.Type, size, size)
} else if t.T == ArrayTy {
// declare our array
refSlice = reflect.New(t.Type).Elem()
} else {
return nil, fmt.Errorf("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 := 32
if t.T == ArrayTy {
elemSize = getFullElemSize(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
}
// 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, end int
err error
)
// if we require a length prefix, find the beginning word and size returned.
if t.requiresLengthPrefix() {
begin, end, err = lengthPrefixPointsTo(index, output)
if err != nil {
return nil, err
}
} else {
returnOutput = output[index : index+32]
}
switch t.T {
case SliceTy:
return forEachUnpack(t, output, begin, end)
case ArrayTy:
return forEachUnpack(t, output, index, t.Size)
case StringTy: // variable arrays are written at the end of the return bytes
return string(output[begin : begin+end]), nil
case IntTy, UintTy:
return readInteger(t.T, t.Kind, returnOutput), nil
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+end], nil
case FixedBytesTy:
return readFixedBytes(t, returnOutput)
case FunctionTy:
return readFunctionType(t, returnOutput)
default:
return nil, fmt.Errorf("abi: unknown type %v", t.T)
}
}
// interprets a 32 byte slice as an offset and then determines which indice to look to decode the type.
func lengthPrefixPointsTo(index int, output []byte) (start int, length int, err error) {
bigOffsetEnd := big.NewInt(0).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 := big.NewInt(0).SetBytes(output[offsetEnd-32 : offsetEnd])
totalSize := big.NewInt(0)
totalSize.Add(totalSize, bigOffsetEnd)
totalSize.Add(totalSize, 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
}
