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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 (
"fmt"
"reflect"
"strings"
"github.com/ethereum/go-ethereum/crypto"
)
// Callable method 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 (m Method) pack(method Method, 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
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 := len(method.Inputs)*32 + 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
}
// 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 (m Method) Sig() string {
types := make([]string, len(m.Inputs))
i := 0
for _, input := range m.Inputs {
types[i] = input.Type.String()
i++
}
return fmt.Sprintf("%v(%v)", m.Name, strings.Join(types, ","))
}
func (m Method) String() string {
inputs := make([]string, len(m.Inputs))
for i, input := range m.Inputs {
inputs[i] = fmt.Sprintf("%v %v", input.Name, input.Type)
}
outputs := make([]string, len(m.Outputs))
for i, output := range m.Outputs {
if len(output.Name) > 0 {
outputs[i] = fmt.Sprintf("%v ", output.Name)
}
outputs[i] += output.Type.String()
}
constant := ""
if m.Const {
constant = "constant "
}
return fmt.Sprintf("function %v(%v) %sreturns(%v)", m.Name, strings.Join(inputs, ", "), constant, strings.Join(outputs, ", "))
}
func (m Method) Id() []byte {
return crypto.Keccak256([]byte(m.Sig()))[:4]
}
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