147 lines
4.1 KiB
Go
147 lines
4.1 KiB
Go
// Copyright 2015 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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"bytes"
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"encoding/json"
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"fmt"
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"io"
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)
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// The ABI holds information about a contract's context and available
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// invokable methods. It will allow you to type check function calls and
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// packs data accordingly.
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type ABI struct {
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Constructor Method
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Methods map[string]Method
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Events map[string]Event
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}
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// JSON returns a parsed ABI interface and error if it failed.
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func JSON(reader io.Reader) (ABI, error) {
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dec := json.NewDecoder(reader)
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var abi ABI
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if err := dec.Decode(&abi); err != nil {
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return ABI{}, err
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}
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return abi, nil
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}
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// Pack the given method name to conform the ABI. Method call's data
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// will consist of method_id, args0, arg1, ... argN. Method id consists
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// of 4 bytes and arguments are all 32 bytes.
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// Method ids are created from the first 4 bytes of the hash of the
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// methods string signature. (signature = baz(uint32,string32))
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func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
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// Fetch the ABI of the requested method
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if name == "" {
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// constructor
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arguments, err := abi.Constructor.Inputs.Pack(args...)
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if err != nil {
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return nil, err
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}
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return arguments, nil
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}
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method, exist := abi.Methods[name]
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if !exist {
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return nil, fmt.Errorf("method '%s' not found", name)
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}
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arguments, err := method.Inputs.Pack(args...)
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if err != nil {
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return nil, err
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}
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// Pack up the method ID too if not a constructor and return
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return append(method.Id(), arguments...), nil
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}
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// Unpack output in v according to the abi specification
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func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
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if len(output) == 0 {
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return fmt.Errorf("abi: unmarshalling empty output")
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}
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// since there can't be naming collisions with contracts and events,
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// we need to decide whether we're calling a method or an event
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if method, ok := abi.Methods[name]; ok {
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if len(output)%32 != 0 {
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return fmt.Errorf("abi: improperly formatted output")
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}
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return method.Outputs.Unpack(v, output)
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} else if event, ok := abi.Events[name]; ok {
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return event.Inputs.Unpack(v, output)
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}
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return fmt.Errorf("abi: could not locate named method or event")
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}
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// UnmarshalJSON implements json.Unmarshaler interface
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func (abi *ABI) UnmarshalJSON(data []byte) error {
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var fields []struct {
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Type string
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Name string
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Constant bool
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Anonymous bool
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Inputs []Argument
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Outputs []Argument
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}
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if err := json.Unmarshal(data, &fields); err != nil {
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return err
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}
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abi.Methods = make(map[string]Method)
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abi.Events = make(map[string]Event)
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for _, field := range fields {
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switch field.Type {
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case "constructor":
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abi.Constructor = Method{
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Inputs: field.Inputs,
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}
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// empty defaults to function according to the abi spec
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case "function", "":
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abi.Methods[field.Name] = Method{
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Name: field.Name,
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Const: field.Constant,
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Inputs: field.Inputs,
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Outputs: field.Outputs,
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}
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case "event":
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abi.Events[field.Name] = Event{
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Name: field.Name,
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Anonymous: field.Anonymous,
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Inputs: field.Inputs,
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}
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}
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}
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return nil
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}
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// MethodById looks up a method by the 4-byte id
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// returns nil if none found
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func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
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for _, method := range abi.Methods {
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if bytes.Equal(method.Id(), sigdata[:4]) {
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return &method, nil
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}
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}
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return nil, fmt.Errorf("no method with id: %#x", sigdata[:4])
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}
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