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// 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/json"
"fmt"
"io"
"math"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
// Executer is an executer method for performing state executions. It takes one
// argument which is the input data and expects output data to be returned as
// multiple 32 byte word length concatenated slice
type Executer func(datain []byte) []byte
// 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 {
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
}
// tests, tests whether the given input would result in a successful
// call. Checks argument list count and matches input to `input`.
func (abi ABI) pack(name string, args ...interface{}) ([]byte, error) {
method := abi.Methods[name]
var ret []byte
for i, a := range args {
input := method.Inputs[i]
packed, err := input.Type.pack(a)
if err != nil {
return nil, fmt.Errorf("`%s` %v", name, err)
}
ret = append(ret, packed...)
}
return ret, 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) {
method, exist := abi.Methods[name]
if !exist {
return nil, fmt.Errorf("method '%s' not found", name)
}
// start with argument count match
if len(args) != len(method.Inputs) {
return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
}
arguments, err := abi.pack(name, args...)
if err != nil {
return nil, err
}
// Set function id
packed := abi.Methods[name].Id()
packed = append(packed, arguments...)
return packed, nil
}
// toGoType parses the input and casts it to the proper type defined by the ABI
// argument in t.
func toGoType(t Argument, input []byte) interface{} {
switch t.Type.T {
case IntTy:
return common.BytesToBig(input)
case UintTy:
return common.BytesToBig(input)
case BoolTy:
return common.BytesToBig(input).Uint64() > 0
case AddressTy:
return common.BytesToAddress(input)
case HashTy:
return common.BytesToHash(input)
}
return nil
}
// Call executes a call and attemps to parse the return values and returns it as
// an interface. It uses the executer method to perform the actual call since
// the abi knows nothing of the lower level calling mechanism.
//
// Call supports all abi types and includes multiple return values. When only
// one item is returned a single interface{} will be returned, if a contract
// method returns multiple values an []interface{} slice is returned.
func (abi ABI) Call(executer Executer, name string, args ...interface{}) interface{} {
callData, err := abi.Pack(name, args...)
if err != nil {
glog.V(logger.Debug).Infoln("pack error:", err)
return nil
}
output := executer(callData)
method := abi.Methods[name]
ret := make([]interface{}, int(math.Max(float64(len(method.Outputs)), float64(len(output)/32))))
for i := 0; i < len(ret); i += 32 {
index := i / 32
ret[index] = toGoType(method.Outputs[index], output[i:i+32])
}
// return single interface
if len(ret) == 1 {
return ret[0]
}
return ret
}
func (abi *ABI) UnmarshalJSON(data []byte) error {
var fields []struct {
Type string
Name string
Const bool
Indexed 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 {
// empty defaults to function according to the abi spec
case "function", "":
abi.Methods[field.Name] = Method{
Name: field.Name,
Const: field.Const,
Inputs: field.Inputs,
Outputs: field.Outputs,
}
case "event":
abi.Events[field.Name] = Event{
Name: field.Name,
Inputs: field.Inputs,
}
}
}
return nil
}
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