// 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"
"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(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
}
// 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
}
