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

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8.1 KiB

// 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"
)
// 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(i int, t Argument, output []byte) (interface{}, error) {
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(common.BytesToBig(output[index : index+32]).Uint64())
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(common.BytesToBig(output[offset : offset+32]).Uint64())
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]
}
// cast bytes to abi return type
switch t.Type.T {
case IntTy:
return common.BytesToBig(returnOutput), nil
case UintTy:
return common.BytesToBig(returnOutput), nil
case BoolTy:
return common.BytesToBig(returnOutput).Uint64() > 0, nil
case AddressTy:
return common.BytesToAddress(returnOutput), nil
case HashTy:
return common.BytesToHash(returnOutput), nil
case BytesTy, FixedBytesTy:
return returnOutput, nil
case StringTy:
return string(returnOutput), nil
}
return nil, fmt.Errorf("abi: unknown type %v", t.Type.T)
}
// Call will unmarshal the output of the call in v. It will return an error if
// invalid type is given or if the output is too short to conform to the ABI
// spec.
//
// Call supports all of the available types and accepts a struct or an interface
// slice if the return is a tuple.
func (abi ABI) Call(executer Executer, v interface{}, name string, args ...interface{}) error {
callData, err := abi.Pack(name, args...)
if err != nil {
return err
}
return abi.unmarshal(v, name, executer(callData))
}
var interSlice = reflect.TypeOf([]interface{}{})
// unmarshal output in v according to the abi specification
func (abi ABI) unmarshal(v interface{}, name string, output []byte) error {
var method = abi.Methods[name]
if len(output) == 0 {
return fmt.Errorf("abi: unmarshalling empty output")
}
value := reflect.ValueOf(v).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 field.Type.AssignableTo(reflectValue.Type()) {
value.Field(j).Set(reflectValue)
break
} else {
return fmt.Errorf("abi: cannot unmarshal %v in to %v", field.Type, reflectValue.Type())
}
}
}
}
case reflect.Slice:
if !value.Type().AssignableTo(interSlice) {
return fmt.Errorf("abi: cannot marshal tuple in to slice %T (only []interface{} is supported)", v)
}
// 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
}
reflectValue := reflect.ValueOf(marshalledValue)
if typ.AssignableTo(reflectValue.Type()) {
value.Set(reflectValue)
} else {
return fmt.Errorf("abi: cannot unmarshal %v in to %v", reflectValue.Type(), value.Type())
}
}
return nil
}
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
}