253 lines
7.5 KiB
Go
253 lines
7.5 KiB
Go
// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package abi
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import (
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"encoding/binary"
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"fmt"
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"math/big"
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"reflect"
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"github.com/ethereum/go-ethereum/common"
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)
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var (
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maxUint256 = big.NewInt(0).Add(
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big.NewInt(0).Exp(big.NewInt(2), big.NewInt(256), nil),
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big.NewInt(-1))
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maxInt256 = big.NewInt(0).Add(
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big.NewInt(0).Exp(big.NewInt(2), big.NewInt(255), nil),
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big.NewInt(-1))
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)
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// reads the integer based on its kind
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func readInteger(typ byte, kind reflect.Kind, b []byte) interface{} {
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switch kind {
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case reflect.Uint8:
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return b[len(b)-1]
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case reflect.Uint16:
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return binary.BigEndian.Uint16(b[len(b)-2:])
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case reflect.Uint32:
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return binary.BigEndian.Uint32(b[len(b)-4:])
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case reflect.Uint64:
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return binary.BigEndian.Uint64(b[len(b)-8:])
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case reflect.Int8:
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return int8(b[len(b)-1])
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case reflect.Int16:
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return int16(binary.BigEndian.Uint16(b[len(b)-2:]))
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case reflect.Int32:
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return int32(binary.BigEndian.Uint32(b[len(b)-4:]))
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case reflect.Int64:
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return int64(binary.BigEndian.Uint64(b[len(b)-8:]))
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default:
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// the only case lefts for integer is int256/uint256.
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// big.SetBytes can't tell if a number is negative, positive on itself.
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// On EVM, if the returned number > max int256, it is negative.
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ret := new(big.Int).SetBytes(b)
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if typ == UintTy {
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return ret
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}
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if ret.Cmp(maxInt256) > 0 {
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ret.Add(maxUint256, big.NewInt(0).Neg(ret))
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ret.Add(ret, big.NewInt(1))
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ret.Neg(ret)
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}
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return ret
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}
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}
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// reads a bool
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func readBool(word []byte) (bool, error) {
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for _, b := range word[:31] {
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if b != 0 {
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return false, errBadBool
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}
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}
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switch word[31] {
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case 0:
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return false, nil
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case 1:
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return true, nil
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default:
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return false, errBadBool
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}
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}
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// A function type is simply the address with the function selection signature at the end.
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// This enforces that standard by always presenting it as a 24-array (address + sig = 24 bytes)
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func readFunctionType(t Type, word []byte) (funcTy [24]byte, err error) {
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if t.T != FunctionTy {
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return [24]byte{}, fmt.Errorf("abi: invalid type in call to make function type byte array")
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}
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if garbage := binary.BigEndian.Uint64(word[24:32]); garbage != 0 {
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err = fmt.Errorf("abi: got improperly encoded function type, got %v", word)
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} else {
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copy(funcTy[:], word[0:24])
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}
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return
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}
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// through reflection, creates a fixed array to be read from
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func readFixedBytes(t Type, word []byte) (interface{}, error) {
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if t.T != FixedBytesTy {
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return nil, fmt.Errorf("abi: invalid type in call to make fixed byte array")
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}
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// convert
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array := reflect.New(t.Type).Elem()
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reflect.Copy(array, reflect.ValueOf(word[0:t.Size]))
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return array.Interface(), nil
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}
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func getFullElemSize(elem *Type) int {
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//all other should be counted as 32 (slices have pointers to respective elements)
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size := 32
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//arrays wrap it, each element being the same size
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for elem.T == ArrayTy {
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size *= elem.Size
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elem = elem.Elem
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}
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return size
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}
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// iteratively unpack elements
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func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error) {
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if size < 0 {
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return nil, fmt.Errorf("cannot marshal input to array, size is negative (%d)", size)
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}
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if start+32*size > len(output) {
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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)
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}
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// this value will become our slice or our array, depending on the type
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var refSlice reflect.Value
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if t.T == SliceTy {
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// declare our slice
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refSlice = reflect.MakeSlice(t.Type, size, size)
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} else if t.T == ArrayTy {
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// declare our array
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refSlice = reflect.New(t.Type).Elem()
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} else {
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return nil, fmt.Errorf("abi: invalid type in array/slice unpacking stage")
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}
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// Arrays have packed elements, resulting in longer unpack steps.
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// Slices have just 32 bytes per element (pointing to the contents).
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elemSize := 32
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if t.T == ArrayTy || t.T == SliceTy {
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elemSize = getFullElemSize(t.Elem)
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}
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for i, j := start, 0; j < size; i, j = i+elemSize, j+1 {
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inter, err := toGoType(i, *t.Elem, output)
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if err != nil {
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return nil, err
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}
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// append the item to our reflect slice
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refSlice.Index(j).Set(reflect.ValueOf(inter))
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}
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// return the interface
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return refSlice.Interface(), nil
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}
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// toGoType parses the output bytes and recursively assigns the value of these bytes
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// into a go type with accordance with the ABI spec.
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func toGoType(index int, t Type, output []byte) (interface{}, error) {
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if index+32 > len(output) {
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return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), index+32)
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}
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var (
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returnOutput []byte
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begin, end int
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err error
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)
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// if we require a length prefix, find the beginning word and size returned.
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if t.requiresLengthPrefix() {
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begin, end, err = lengthPrefixPointsTo(index, output)
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if err != nil {
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return nil, err
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}
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} else {
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returnOutput = output[index : index+32]
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}
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switch t.T {
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case SliceTy:
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return forEachUnpack(t, output, begin, end)
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case ArrayTy:
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return forEachUnpack(t, output, index, t.Size)
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case StringTy: // variable arrays are written at the end of the return bytes
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return string(output[begin : begin+end]), nil
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case IntTy, UintTy:
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return readInteger(t.T, t.Kind, returnOutput), nil
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case BoolTy:
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return readBool(returnOutput)
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case AddressTy:
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return common.BytesToAddress(returnOutput), nil
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case HashTy:
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return common.BytesToHash(returnOutput), nil
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case BytesTy:
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return output[begin : begin+end], nil
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case FixedBytesTy:
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return readFixedBytes(t, returnOutput)
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case FunctionTy:
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return readFunctionType(t, returnOutput)
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default:
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return nil, fmt.Errorf("abi: unknown type %v", t.T)
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}
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}
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// interprets a 32 byte slice as an offset and then determines which indice to look to decode the type.
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func lengthPrefixPointsTo(index int, output []byte) (start int, length int, err error) {
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bigOffsetEnd := big.NewInt(0).SetBytes(output[index : index+32])
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bigOffsetEnd.Add(bigOffsetEnd, common.Big32)
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outputLength := big.NewInt(int64(len(output)))
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if bigOffsetEnd.Cmp(outputLength) > 0 {
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return 0, 0, fmt.Errorf("abi: cannot marshal in to go slice: offset %v would go over slice boundary (len=%v)", bigOffsetEnd, outputLength)
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}
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if bigOffsetEnd.BitLen() > 63 {
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return 0, 0, fmt.Errorf("abi offset larger than int64: %v", bigOffsetEnd)
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}
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offsetEnd := int(bigOffsetEnd.Uint64())
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lengthBig := big.NewInt(0).SetBytes(output[offsetEnd-32 : offsetEnd])
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totalSize := big.NewInt(0)
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totalSize.Add(totalSize, bigOffsetEnd)
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totalSize.Add(totalSize, lengthBig)
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if totalSize.BitLen() > 63 {
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return 0, 0, fmt.Errorf("abi length larger than int64: %v", totalSize)
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}
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if totalSize.Cmp(outputLength) > 0 {
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return 0, 0, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %v require %v", outputLength, totalSize)
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}
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start = int(bigOffsetEnd.Uint64())
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length = int(lengthBig.Uint64())
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return
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}
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