path: root/accounts/abi/unpack.go

// Copyright 2015 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"
)

// toGoSliceType parses the input and casts it to the proper slice defined by the ABI
// argument in T.
func toGoSlice(i int, t Argument, output []byte) (interface{}, error) {
    index := i * 32
    // The slice must, at very least be large enough for the index+32 which is exactly the size required
    // for the [offset in output, size of offset].
    if index+32 > len(output) {
        return nil, fmt.Errorf("abi: cannot marshal in to go slice: insufficient size output %d require %d", len(output), index+32)
    }
    elem := t.Type.Elem

    // first we need to create a slice of the type
    var refSlice reflect.Value
    switch elem.T {
    case IntTy, UintTy, BoolTy:
        // create a new reference slice matching the element type
        switch t.Type.Kind {
        case reflect.Bool:
            refSlice = reflect.ValueOf([]bool(nil))
        case reflect.Uint8:
            refSlice = reflect.ValueOf([]uint8(nil))
        case reflect.Uint16:
            refSlice = reflect.ValueOf([]uint16(nil))
        case reflect.Uint32:
            refSlice = reflect.ValueOf([]uint32(nil))
        case reflect.Uint64:
            refSlice = reflect.ValueOf([]uint64(nil))
        case reflect.Int8:
            refSlice = reflect.ValueOf([]int8(nil))
        case reflect.Int16:
            refSlice = reflect.ValueOf([]int16(nil))
        case reflect.Int32:
            refSlice = reflect.ValueOf([]int32(nil))
        case reflect.Int64:
            refSlice = reflect.ValueOf([]int64(nil))
        default:
            refSlice = reflect.ValueOf([]*big.Int(nil))
        }
    case AddressTy: // address must be of slice Address
        refSlice = reflect.ValueOf([]common.Address(nil))
    case HashTy: // hash must be of slice hash
        refSlice = reflect.ValueOf([]common.Hash(nil))
    case FixedBytesTy:
        refSlice = reflect.ValueOf([][]byte(nil))
    default: // no other types are supported
        return nil, fmt.Errorf("abi: unsupported slice type %v", elem.T)
    }

    var slice []byte
    var size int
    var offset int
    if t.Type.IsSlice {
        // get the offset which determines the start of this array ...
        offset = int(binary.BigEndian.Uint64(output[index+24 : index+32]))
        if offset+32 > len(output) {
            return nil, fmt.Errorf("abi: cannot marshal in to go slice: offset %d would go over slice boundary (len=%d)", len(output), offset+32)
        }

        slice = output[offset:]
        // ... starting with the size of the array in elements ...
        size = int(binary.BigEndian.Uint64(slice[24:32]))
        slice = slice[32:]
        // ... and make sure that we've at the very least the amount of bytes
        // available in the buffer.
        if size*32 > len(slice) {
            return nil, fmt.Errorf("abi: cannot marshal in to go slice: insufficient size output %d require %d", len(output), offset+32+size*32)
        }

        // reslice to match the required size
        slice = slice[:size*32]
    } else if t.Type.IsArray {
        //get the number of elements in the array
        size = t.Type.SliceSize

        //check to make sure array size matches up
        if index+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), index+32*size)
        }
        //slice is there for a fixed amount of times
        slice = output[index : index+size*32]
    }

    for i := 0; i < size; i++ {
        var (
            inter        interface{}             // interface type
            returnOutput = slice[i*32 : i*32+32] // the return output
            err          error
        )
        // set inter to the correct type (cast)
        switch elem.T {
        case IntTy, UintTy:
            inter = readInteger(t.Type.Kind, returnOutput)
        case BoolTy:
            inter, err = readBool(returnOutput)
            if err != nil {
                return nil, err
            }
        case AddressTy:
            inter = common.BytesToAddress(returnOutput)
        case HashTy:
            inter = common.BytesToHash(returnOutput)
        case FixedBytesTy:
            inter = returnOutput
        }
        // append the item to our reflect slice
        refSlice = reflect.Append(refSlice, reflect.ValueOf(inter))
    }

    // return the interface
    return refSlice.Interface(), nil
}

func readInteger(kind reflect.Kind, b []byte) interface{} {
    switch kind {
    case reflect.Uint8:
        return uint8(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:
        return new(big.Int).SetBytes(b)
    }
}

func readBool(word []byte) (bool, error) {
    if len(word) != 32 {
        return false, fmt.Errorf("abi: fatal error: incorrect word length")
    }

    for i, b := range word {
        if b != 0 && i != 31 {
            return false, errBadBool
        }
    }
    switch word[31] {
    case 0:
        return false, nil
    case 1:
        return true, nil
    default:
        return false, errBadBool
    }

}

// toGoType parses the input and casts it to the proper type defined by the ABI
// argument in T.
func toGoType(i int, t Argument, output []byte) (interface{}, error) {
    // we need to treat slices differently
    if (t.Type.IsSlice || t.Type.IsArray) && t.Type.T != BytesTy && t.Type.T != StringTy && t.Type.T != FixedBytesTy && t.Type.T != FunctionTy {
        return toGoSlice(i, t, output)
    }

    index := i * 32
    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)
    }

    // Parse the given index output and check whether we need to read
    // a different offset and length based on the type (i.e. string, bytes)
    var returnOutput []byte
    switch t.Type.T {
    case StringTy, BytesTy: // variable arrays are written at the end of the return bytes
        // parse offset from which we should start reading
        offset := int(binary.BigEndian.Uint64(output[index+24 : index+32]))
        if offset+32 > len(output) {
            return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), offset+32)
        }
        // parse the size up until we should be reading
        size := int(binary.BigEndian.Uint64(output[offset+24 : offset+32]))
        if offset+32+size > len(output) {
            return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), offset+32+size)
        }

        // get the bytes for this return value
        returnOutput = output[offset+32 : offset+32+size]
    default:
        returnOutput = output[index : index+32]
    }

    // convert the bytes to whatever is specified by the ABI.
    switch t.Type.T {
    case IntTy, UintTy:
        return readInteger(t.Type.Kind, returnOutput), nil
    case BoolTy:
        return readBool(returnOutput)
    case AddressTy:
        return common.BytesToAddress(returnOutput), nil
    case HashTy:
        return common.BytesToHash(returnOutput), nil
    case BytesTy, FixedBytesTy, FunctionTy:
        return returnOutput, nil
    case StringTy:
        return string(returnOutput), nil
    }
    return nil, fmt.Errorf("abi: unknown type %v", t.Type.T)
}