330 lines
10 KiB
Go
330 lines
10 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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"errors"
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"fmt"
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"math"
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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 is the maximum value that can be represented by a uint256.
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MaxUint256 = new(big.Int).Sub(new(big.Int).Lsh(common.Big1, 256), common.Big1)
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// MaxInt256 is the maximum value that can be represented by a int256.
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MaxInt256 = new(big.Int).Sub(new(big.Int).Lsh(common.Big1, 255), common.Big1)
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)
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// ReadInteger reads the integer based on its kind and returns the appropriate value.
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func ReadInteger(typ Type, b []byte) (interface{}, error) {
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ret := new(big.Int).SetBytes(b)
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if typ.T == UintTy {
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u64, isu64 := ret.Uint64(), ret.IsUint64()
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switch typ.Size {
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case 8:
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if !isu64 || u64 > math.MaxUint8 {
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return nil, errBadUint8
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}
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return byte(u64), nil
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case 16:
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if !isu64 || u64 > math.MaxUint16 {
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return nil, errBadUint16
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}
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return uint16(u64), nil
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case 32:
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if !isu64 || u64 > math.MaxUint32 {
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return nil, errBadUint32
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}
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return uint32(u64), nil
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case 64:
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if !isu64 {
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return nil, errBadUint64
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}
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return u64, nil
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default:
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// the only case left for unsigned integer is uint256.
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return ret, nil
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}
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}
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// big.SetBytes can't tell if a number is negative or positive in itself.
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// On EVM, if the returned number > max int256, it is negative.
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// A number is > max int256 if the bit at position 255 is set.
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if ret.Bit(255) == 1 {
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ret.Add(MaxUint256, new(big.Int).Neg(ret))
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ret.Add(ret, common.Big1)
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ret.Neg(ret)
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}
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i64, isi64 := ret.Int64(), ret.IsInt64()
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switch typ.Size {
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case 8:
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if !isi64 || i64 < math.MinInt8 || i64 > math.MaxInt8 {
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return nil, errBadInt8
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}
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return int8(i64), nil
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case 16:
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if !isi64 || i64 < math.MinInt16 || i64 > math.MaxInt16 {
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return nil, errBadInt16
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}
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return int16(i64), nil
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case 32:
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if !isi64 || i64 < math.MinInt32 || i64 > math.MaxInt32 {
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return nil, errBadInt32
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}
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return int32(i64), nil
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case 64:
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if !isi64 {
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return nil, errBadInt64
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}
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return i64, nil
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default:
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// the only case left for integer is int256
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return ret, nil
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}
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}
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// readBool 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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//
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// readFunctionType 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{}, errors.New("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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// ReadFixedBytes uses reflection to create 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, errors.New("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.GetType()).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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// forEachUnpack 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 into 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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switch t.T {
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case SliceTy:
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// declare our slice
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refSlice = reflect.MakeSlice(t.GetType(), size, size)
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case ArrayTy:
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// declare our array
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refSlice = reflect.New(t.GetType()).Elem()
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default:
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return nil, errors.New("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 := getTypeSize(*t.Elem)
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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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func forTupleUnpack(t Type, output []byte) (interface{}, error) {
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retval := reflect.New(t.GetType()).Elem()
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virtualArgs := 0
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for index, elem := range t.TupleElems {
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marshalledValue, err := toGoType((index+virtualArgs)*32, *elem, output)
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if err != nil {
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return nil, err
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}
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if elem.T == ArrayTy && !isDynamicType(*elem) {
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// If we have a static array, like [3]uint256, these are coded as
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// just like uint256,uint256,uint256.
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// This means that we need to add two 'virtual' arguments when
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// we count the index from now on.
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//
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// Array values nested multiple levels deep are also encoded inline:
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// [2][3]uint256: uint256,uint256,uint256,uint256,uint256,uint256
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//
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// Calculate the full array size to get the correct offset for the next argument.
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// Decrement it by 1, as the normal index increment is still applied.
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virtualArgs += getTypeSize(*elem)/32 - 1
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} else if elem.T == TupleTy && !isDynamicType(*elem) {
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// If we have a static tuple, like (uint256, bool, uint256), these are
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// coded as just like uint256,bool,uint256
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virtualArgs += getTypeSize(*elem)/32 - 1
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}
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retval.Field(index).Set(reflect.ValueOf(marshalledValue))
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}
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return retval.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, length 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, length, 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 TupleTy:
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if isDynamicType(t) {
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begin, err := tuplePointsTo(index, output)
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if err != nil {
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return nil, err
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}
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return forTupleUnpack(t, output[begin:])
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}
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return forTupleUnpack(t, output[index:])
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case SliceTy:
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return forEachUnpack(t, output[begin:], 0, length)
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case ArrayTy:
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if isDynamicType(*t.Elem) {
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offset := binary.BigEndian.Uint64(returnOutput[len(returnOutput)-8:])
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if offset > uint64(len(output)) {
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return nil, fmt.Errorf("abi: toGoType offset greater than output length: offset: %d, len(output): %d", offset, len(output))
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}
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return forEachUnpack(t, output[offset:], 0, t.Size)
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}
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return forEachUnpack(t, output[index:], 0, 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+length]), nil
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case IntTy, UintTy:
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return ReadInteger(t, returnOutput)
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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+length], 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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// lengthPrefixPointsTo interprets a 32 byte slice as an offset and then determines which indices 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 := new(big.Int).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 := new(big.Int).SetBytes(output[offsetEnd-32 : offsetEnd])
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totalSize := new(big.Int).Add(bigOffsetEnd, 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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// tuplePointsTo resolves the location reference for dynamic tuple.
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func tuplePointsTo(index int, output []byte) (start int, err error) {
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offset := new(big.Int).SetBytes(output[index : index+32])
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outputLen := big.NewInt(int64(len(output)))
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if offset.Cmp(outputLen) > 0 {
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return 0, fmt.Errorf("abi: cannot marshal in to go slice: offset %v would go over slice boundary (len=%v)", offset, outputLen)
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}
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if offset.BitLen() > 63 {
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return 0, fmt.Errorf("abi offset larger than int64: %v", offset)
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}
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return int(offset.Uint64()), nil
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}
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