// 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"
"encoding/json"
"fmt"
"io"
"math/big"
"reflect"
"strings"
"github.com/ethereum/go-ethereum/common"
)
// The ABI holds information about a contract's context and available
// invokable methods. It will allow you to type check function calls and
// packs data accordingly.
type ABI struct {
Constructor Method
Methods map[string]Method
Events map[string]Event
}
// JSON returns a parsed ABI interface and error if it failed.
func JSON(reader io.Reader) (ABI, error) {
dec := json.NewDecoder(reader)
var abi ABI
if err := dec.Decode(&abi); err != nil {
return ABI{}, err
}
return abi, nil
}
// Pack the given method name to conform the ABI. Method call's data
// will consist of method_id, args0, arg1, ... argN. Method id consists
// of 4 bytes and arguments are all 32 bytes.
// Method ids are created from the first 4 bytes of the hash of the
// methods string signature. (signature = baz(uint32,string32))
func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
// Fetch the ABI of the requested method
var method Method
if name == "" {
method = abi.Constructor
} else {
m, exist := abi.Methods[name]
if !exist {
return nil, fmt.Errorf("method '%s' not found", name)
}
method = m
}
arguments, err := method.pack(method, args...)
if err != nil {
return nil, err
}
// Pack up the method ID too if not a constructor and return
if name == "" {
return arguments, nil
}
return append(method.Id(), arguments...), nil
}
// 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
)
// set inter to the correct type (cast)
switch elem.T {
case IntTy, UintTy:
inter = readInteger(t.Type.Kind, returnOutput)
case BoolTy:
inter = !allZero(returnOutput)
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 allZero(b []byte) bool {
for _, byte := range b {
if byte != 0 {
return false
}
}
return true
}
// 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 !allZero(returnOutput), nil
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)
}
// these variable are used to determine certain types during type assertion for
// assignment.
var (
r_interSlice = reflect.TypeOf([]interface{}{})
r_hash = reflect.TypeOf(common.Hash{})
r_bytes = reflect.TypeOf([]byte{})
r_byte = reflect.TypeOf(byte(0))
)
// Unpack output in v according to the abi specification
func (abi ABI) Unpack(v interface{}, name string, output []byte) error {
var method = abi.Methods[name]
if len(output) == 0 {
return fmt.Errorf("abi: unmarshalling empty output")
}
// make sure the passed value is a pointer
valueOf := reflect.ValueOf(v)
if reflect.Ptr != valueOf.Kind() {
return fmt.Errorf("abi: Unpack(non-pointer %T)", v)
}
var (
value = valueOf.Elem()
typ = value.Type()
)
if len(method.Outputs) > 1 {
switch value.Kind() {
// struct will match named return values to the struct's field
// names
case reflect.Struct:
for i := 0; i < len(method.Outputs); i++ {
marshalledValue, err := toGoType(i, method.Outputs[i], output)
if err != nil {
return err
}
reflectValue := reflect.ValueOf(marshalledValue)
for j := 0; j < typ.NumField(); j++ {
field := typ.Field(j)
// TODO read tags: `abi:"fieldName"`
if field.Name == strings.ToUpper(method.Outputs[i].Name[:1])+method.Outputs[i].Name[1:] {
if err := set(value.Field(j), reflectValue, method.Outputs[i]); err != nil {
return err
}
}
}
}
case reflect.Slice:
if !value.Type().AssignableTo(r_interSlice) {
return fmt.Errorf("abi: cannot marshal tuple in to slice %T (only []interface{} is supported)", v)
}
// if the slice already contains values, set those instead of the interface slice itself.
if value.Len() > 0 {
if len(method.Outputs) > value.Len() {
return fmt.Errorf("abi: cannot marshal in to slices of unequal size (require: %v, got: %v)", len(method.Outputs), value.Len())
}
for i := 0; i < len(method.Outputs); i++ {
marshalledValue, err := toGoType(i, method.Outputs[i], output)
if err != nil {
return err
}
reflectValue := reflect.ValueOf(marshalledValue)
if err := set(value.Index(i).Elem(), reflectValue, method.Outputs[i]); err != nil {
return err
}
}
return nil
}
// create a new slice and start appending the unmarshalled
// values to the new interface slice.
z := reflect.MakeSlice(typ, 0, len(method.Outputs))
for i := 0; i < len(method.Outputs); i++ {
marshalledValue, err := toGoType(i, method.Outputs[i], output)
if err != nil {
return err
}
z = reflect.Append(z, reflect.ValueOf(marshalledValue))
}
value.Set(z)
default:
return fmt.Errorf("abi: cannot unmarshal tuple in to %v", typ)
}
} else {
marshalledValue, err := toGoType(0, method.Outputs[0], output)
if err != nil {
return err
}
if err := set(value, reflect.ValueOf(marshalledValue), method.Outputs[0]); err != nil {
return err
}
}
return nil
}
func (abi *ABI) UnmarshalJSON(data []byte) error {
var fields []struct {
Type string
Name string
Constant bool
Indexed bool
Anonymous bool
Inputs []Argument
Outputs []Argument
}
if err := json.Unmarshal(data, &fields); err != nil {
return err
}
abi.Methods = make(map[string]Method)
abi.Events = make(map[string]Event)
for _, field := range fields {
switch field.Type {
case "constructor":
abi.Constructor = Method{
Inputs: field.Inputs,
}
// empty defaults to function according to the abi spec
case "function", "":
abi.Methods[field.Name] = Method{
Name: field.Name,
Const: field.Constant,
Inputs: field.Inputs,
Outputs: field.Outputs,
}
case "event":
abi.Events[field.Name] = Event{
Name: field.Name,
Anonymous: field.Anonymous,
Inputs: field.Inputs,
}
}
}
return nil
}
