Official Go implementation of the Ethereum protocol
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go-ethereum/accounts/abi/abi.go

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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 (
"bytes"
"encoding/json"
"errors"
"fmt"
"io"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
)
// 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
Errors map[string]Error
// Additional "special" functions introduced in solidity v0.6.0.
// It's separated from the original default fallback. Each contract
// can only define one fallback and receive function.
Fallback Method // Note it's also used to represent legacy fallback before v0.6.0
Receive Method
}
// 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
if name == "" {
// constructor
arguments, err := abi.Constructor.Inputs.Pack(args...)
if err != nil {
return nil, err
}
return arguments, nil
}
method, exist := abi.Methods[name]
if !exist {
return nil, fmt.Errorf("method '%s' not found", name)
}
arguments, err := method.Inputs.Pack(args...)
if err != nil {
return nil, err
}
// Pack up the method ID too if not a constructor and return
return append(method.ID, arguments...), nil
}
func (abi ABI) getArguments(name string, data []byte) (Arguments, error) {
// since there can't be naming collisions with contracts and events,
// we need to decide whether we're calling a method or an event
var args Arguments
if method, ok := abi.Methods[name]; ok {
if len(data)%32 != 0 {
return nil, fmt.Errorf("abi: improperly formatted output: %q - Bytes: %+v", data, data)
}
args = method.Outputs
}
if event, ok := abi.Events[name]; ok {
args = event.Inputs
}
if args == nil {
return nil, fmt.Errorf("abi: could not locate named method or event: %s", name)
}
return args, nil
}
// Unpack unpacks the output according to the abi specification.
func (abi ABI) Unpack(name string, data []byte) ([]interface{}, error) {
args, err := abi.getArguments(name, data)
if err != nil {
return nil, err
}
return args.Unpack(data)
}
// UnpackIntoInterface unpacks the output in v according to the abi specification.
// It performs an additional copy. Please only use, if you want to unpack into a
// structure that does not strictly conform to the abi structure (e.g. has additional arguments)
func (abi ABI) UnpackIntoInterface(v interface{}, name string, data []byte) error {
args, err := abi.getArguments(name, data)
if err != nil {
return err
}
unpacked, err := args.Unpack(data)
if err != nil {
return err
}
return args.Copy(v, unpacked)
}
// UnpackIntoMap unpacks a log into the provided map[string]interface{}.
func (abi ABI) UnpackIntoMap(v map[string]interface{}, name string, data []byte) (err error) {
args, err := abi.getArguments(name, data)
if err != nil {
return err
}
return args.UnpackIntoMap(v, data)
}
// UnmarshalJSON implements json.Unmarshaler interface.
func (abi *ABI) UnmarshalJSON(data []byte) error {
var fields []struct {
Type string
Name string
Inputs []Argument
Outputs []Argument
// Status indicator which can be: "pure", "view",
// "nonpayable" or "payable".
StateMutability string
// Deprecated Status indicators, but removed in v0.6.0.
Constant bool // True if function is either pure or view
Payable bool // True if function is payable
// Event relevant indicator represents the event is
// declared as anonymous.
Anonymous bool
}
if err := json.Unmarshal(data, &fields); err != nil {
return err
}
abi.Methods = make(map[string]Method)
abi.Events = make(map[string]Event)
abi.Errors = make(map[string]Error)
for _, field := range fields {
switch field.Type {
case "constructor":
abi.Constructor = NewMethod("", "", Constructor, field.StateMutability, field.Constant, field.Payable, field.Inputs, nil)
case "function":
name := ResolveNameConflict(field.Name, func(s string) bool { _, ok := abi.Methods[s]; return ok })
abi.Methods[name] = NewMethod(name, field.Name, Function, field.StateMutability, field.Constant, field.Payable, field.Inputs, field.Outputs)
case "fallback":
// New introduced function type in v0.6.0, check more detail
// here https://solidity.readthedocs.io/en/v0.6.0/contracts.html#fallback-function
if abi.HasFallback() {
return errors.New("only single fallback is allowed")
}
abi.Fallback = NewMethod("", "", Fallback, field.StateMutability, field.Constant, field.Payable, nil, nil)
case "receive":
// New introduced function type in v0.6.0, check more detail
// here https://solidity.readthedocs.io/en/v0.6.0/contracts.html#fallback-function
if abi.HasReceive() {
return errors.New("only single receive is allowed")
}
if field.StateMutability != "payable" {
return errors.New("the statemutability of receive can only be payable")
}
abi.Receive = NewMethod("", "", Receive, field.StateMutability, field.Constant, field.Payable, nil, nil)
case "event":
name := ResolveNameConflict(field.Name, func(s string) bool { _, ok := abi.Events[s]; return ok })
abi.Events[name] = NewEvent(name, field.Name, field.Anonymous, field.Inputs)
case "error":
// Errors cannot be overloaded or overridden but are inherited,
// no need to resolve the name conflict here.
abi.Errors[field.Name] = NewError(field.Name, field.Inputs)
default:
return fmt.Errorf("abi: could not recognize type %v of field %v", field.Type, field.Name)
}
}
return nil
}
// MethodById looks up a method by the 4-byte id,
// returns nil if none found.
func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
if len(sigdata) < 4 {
return nil, fmt.Errorf("data too short (%d bytes) for abi method lookup", len(sigdata))
}
for _, method := range abi.Methods {
if bytes.Equal(method.ID, sigdata[:4]) {
return &method, nil
}
}
return nil, fmt.Errorf("no method with id: %#x", sigdata[:4])
}
// EventByID looks an event up by its topic hash in the
// ABI and returns nil if none found.
func (abi *ABI) EventByID(topic common.Hash) (*Event, error) {
for _, event := range abi.Events {
if bytes.Equal(event.ID.Bytes(), topic.Bytes()) {
return &event, nil
}
}
return nil, fmt.Errorf("no event with id: %#x", topic.Hex())
}
// HasFallback returns an indicator whether a fallback function is included.
func (abi *ABI) HasFallback() bool {
return abi.Fallback.Type == Fallback
}
// HasReceive returns an indicator whether a receive function is included.
func (abi *ABI) HasReceive() bool {
return abi.Receive.Type == Receive
}
// revertSelector is a special function selector for revert reason unpacking.
var revertSelector = crypto.Keccak256([]byte("Error(string)"))[:4]
// UnpackRevert resolves the abi-encoded revert reason. According to the solidity
// spec https://solidity.readthedocs.io/en/latest/control-structures.html#revert,
// the provided revert reason is abi-encoded as if it were a call to a function
// `Error(string)`. So it's a special tool for it.
func UnpackRevert(data []byte) (string, error) {
if len(data) < 4 {
return "", errors.New("invalid data for unpacking")
}
if !bytes.Equal(data[:4], revertSelector) {
return "", errors.New("invalid data for unpacking")
}
typ, _ := NewType("string", "", nil)
unpacked, err := (Arguments{{Type: typ}}).Unpack(data[4:])
if err != nil {
return "", err
}
return unpacked[0].(string), nil
}