// 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 (
"fmt"
"reflect"
"strings"
"github.com/ethereum/go-ethereum/crypto"
)
// Method represents a callable given a `Name` and whether the method is a constant.
// If the method is `Const` no transaction needs to be created for this
// particular Method call. It can easily be simulated using a local VM.
// For example a `Balance()` method only needs to retrieve something
// from the storage and therefor requires no Tx to be send to the
// network. A method such as `Transact` does require a Tx and thus will
// be flagged `true`.
// Input specifies the required input parameters for this gives method.
type Method struct {
Name string
Const bool
Inputs []Argument
Outputs []Argument
}
func (method Method) pack(args ...interface{}) ([]byte, error) {
// Make sure arguments match up and pack them
if len(args) != len(method.Inputs) {
return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
}
// variable input is the output appended at the end of packed
// output. This is used for strings and bytes types input.
var variableInput []byte
// input offset is the bytes offset for packed output
inputOffset := 0
for _, input := range method.Inputs {
if input.Type.T == ArrayTy {
inputOffset += (32 * input.Type.Size)
} else {
inputOffset += 32
}
}
var ret []byte
for i, a := range args {
input := method.Inputs[i]
// pack the input
packed, err := input.Type.pack(reflect.ValueOf(a))
if err != nil {
return nil, fmt.Errorf("`%s` %v", method.Name, err)
}
// check for a slice type (string, bytes, slice)
if input.Type.requiresLengthPrefix() {
// calculate the offset
offset := inputOffset + len(variableInput)
// set the offset
ret = append(ret, packNum(reflect.ValueOf(offset))...)
// Append the packed output to the variable input. The variable input
// will be appended at the end of the input.
variableInput = append(variableInput, packed...)
} else {
// append the packed value to the input
ret = append(ret, packed...)
}
}
// append the variable input at the end of the packed input
ret = append(ret, variableInput...)
return ret, nil
}
// unpacks a method return tuple into a struct of corresponding go types
//
// Unpacking can be done into a struct or a slice/array.
func (method Method) tupleUnpack(v interface{}, outputSlice []byte) error {
// 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()
kind = value.Kind()
)
if err := requireUnpackKind(value, typ, kind, method.Outputs, false); err != nil {
return err
}
j := 0
for i, output := range method.Outputs {
marshalledValue, err := toGoType((i+j)*32, ouptut.Type, outputSlice)
if err != nil {
return err
}
if output.Type.T == ArrayTy {
// combined index ('i' + 'j') need to be adjusted only by size of array, thus
// we need to decrement 'j' because 'i' was incremented
j += output.Type.Size - 1
}
reflectValue := reflect.ValueOf(marshalledValue)
switch kind {
case reflect.Struct:
for j := 0; j < typ.NumField(); j++ {
field := typ.Field(j)
// TODO read tags: `abi:"fieldName"`
if field.Name == strings.ToUpper(output.Name[:1])+output.Name[1:] {
if err := set(value.Field(j), reflectValue, output); err != nil {
return err
}
}
}
case reflect.Slice, reflect.Array:
v := value.Index(i)
if err := requireAssignable(v, reflectValue); err != nil {
return err
}
if err := set(v.Elem(), reflectValue, output); err != nil {
return err
}
}
}
return nil
}
func (method Method) isTupleReturn() bool { return len(method.Outputs) > 1 }
func (method Method) singleUnpack(v interface{}, output []byte) error {
// 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)
}
value := valueOf.Elem()
marshalledValue, err := toGoType(0, method.Outputs[0].Type, output)
if err != nil {
return err
}
return set(value, reflect.ValueOf(marshalledValue), method.Outputs[0])
}
// Sig returns the methods string signature according to the ABI spec.
//
// Example
//
// function foo(uint32 a, int b) = "foo(uint32,int256)"
//
// Please note that "int" is substitute for its canonical representation "int256"
func (method Method) Sig() string {
types := make([]string, len(method.Inputs))
i := 0
for _, input := range method.Inputs {
types[i] = input.Type.String()
i++
}
return fmt.Sprintf("%v(%v)", method.Name, strings.Join(types, ","))
}
func (method Method) String() string {
inputs := make([]string, len(method.Inputs))
for i, input := range method.Inputs {
inputs[i] = fmt.Sprintf("%v %v", input.Name, input.Type)
}
outputs := make([]string, len(method.Outputs))
for i, output := range method.Outputs {
if len(output.Name) > 0 {
outputs[i] = fmt.Sprintf("%v ", output.Name)
}
outputs[i] += output.Type.String()
}
constant := ""
if method.Const {
constant = "constant "
}
return fmt.Sprintf("function %v(%v) %sreturns(%v)", method.Name, strings.Join(inputs, ", "), constant, strings.Join(outputs, ", "))
}
func (method Method) Id() []byte {
return crypto.Keccak256([]byte(method.Sig()))[:4]
}
