【以太坊源码go-ethereum阅读】accounts/abi/method.go

// 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"
	"strings"

	"github.com/ethereum/go-ethereum/crypto"
)

// FunctionType represents different types of functions a contract might have.
// FunctionType表示合同可能具有的不同类型的功能。
type FunctionType int

const (
	// Constructor represents the constructor of the contract.
	// 构造函数代表合约的构造函数。
	// The constructor function is called while deploying a contract.
	// 在部署合约时调用构造函数。
	Constructor FunctionType = iota
	// Fallback represents the fallback function.
	// 回退表示回退功能。
	// This function is executed if no other function matches the given function
	// signature and no receive function is specified.
	// 如果没有其他函数与给定的函数签名匹配，并且没有指定接收函数，则执行此函数。
	Fallback
	// Receive represents the receive function.
	// Receive表示接收函数。
	// This function is executed on plain Ether transfers.
	// 此功能在普通以太币传输上执行。
	Receive
	// Function represents a normal function.
	// Function 表示正常函数。
	Function
)

// Method represents a callable given a `Name` and whether the method is a constant.
// Method表示给定“Name”的可调用对象，以及该方法是否为常量。
// 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 therefore requires no Tx to be sent to the
// network. A method such as `Transact` does require a Tx and thus will
// be flagged `false`.
// 如果方法是“Const”，则不需要为此特定方法调用创建事务。它可以很容易地使用本地虚拟机进行模拟。
// 例如，“Balance（）”方法只需要从存储器中检索一些东西，因此不需要向网络发送Tx。诸如“Transact-”之类的方法确实需要Tx，因此将被标记为“false”。
// Input specifies the required input parameters for this gives method.
// Input指定了此给定方法所需的输入参数。
type Method struct {
	// Name is the method name used for internal representation. It's derived from
	// the raw name and a suffix will be added in the case of a function overload.
	// Name是用于内部表示的方法名称。它源自原始名称，在函数重载的情况下会添加后缀。
	// e.g.
	// These are two functions that have the same name: 这是两个同名的函数
	// * foo(int,int)
	// * foo(uint,uint)
	// The method name of the first one will be resolved as foo while the second one
	// will be resolved as foo0.
	// 第一个方法的方法名将解析为foo，而第二个方法的名称将解析为foo0。
	Name    string
	RawName string // RawName is the raw method name parsed from ABI RawName是从ABI解析的原始方法名称

	// Type indicates whether the method is a
	// special fallback introduced in solidity v0.6.0
	// 类型表示该方法是否是solidity v0.6.0中引入的特殊回退
	Type FunctionType

	// StateMutability indicates the mutability state of method,
	// the default value is nonpayable. It can be empty if the abi
	// is generated by legacy compiler.
	// StateMutability表示方法的可变状态，默认值为nonpayable。如果abi是由遗留编译器生成的，那么它可以是空的。
	StateMutability string

	// Legacy indicators generated by compiler before v0.6.0        v0.6.0之前的编译器生成的旧指示符
	Constant bool
	Payable  bool

	Inputs  Arguments
	Outputs Arguments
	str     string
	// Sig returns the methods string signature according to the ABI spec. Sig根据ABI规范返回方法字符串签名。
	// e.g.		function foo(uint32 a, int b) = "foo(uint32,int256)"
	// Please note that "int" is substitute for its canonical representation "int256" 请注意，“int”可替代其规范表示“int256”
	Sig string
	// ID returns the canonical representation of the method's signature used by the
	// abi definition to identify method names and types.
	// ID返回abi定义用于标识方法名称和类型的方法签名的规范表示。
	ID []byte
}

// NewMethod creates a new Method.
// NewMethod将创建一个新方法。
// A method should always be created using
// NewMethod. 应始终使用NewMethod创建方法。
// It also precomputes the sig representation and the string representation
// of the method.
// 它还预先计算方法的sig表示和字符串表示。
func NewMethod(name string, rawName string, funType FunctionType, mutability string, isConst, isPayable bool, inputs Arguments, outputs Arguments) Method {
	var (
		types       = make([]string, len(inputs))
		inputNames  = make([]string, len(inputs))
		outputNames = make([]string, len(outputs))
	)
	for i, input := range inputs {
		inputNames[i] = fmt.Sprintf("%v %v", input.Type, input.Name)
		types[i] = input.Type.String()
	}
	for i, output := range outputs {
		outputNames[i] = output.Type.String()
		if len(output.Name) > 0 {
			outputNames[i] += fmt.Sprintf(" %v", output.Name)
		}
	}
	// calculate the signature and method id. Note only function
	// has meaningful signature and id.
	// 计算签名和方法id。注意，只有函数具有有意义的签名和id。
	var (
		sig string
		id  []byte
	)
	if funType == Function {
		sig = fmt.Sprintf("%v(%v)", rawName, strings.Join(types, ","))
		id = crypto.Keccak256([]byte(sig))[:4]
	}
	// Extract meaningful state mutability of solidity method.
	// 提取solidity方法的有意义状态可变性。
	// If it's default value, never print it.
	// 如果它是默认值，则永远不要打印它。
	state := mutability
	if state == "nonpayable" {
		state = ""
	}
	if state != "" {
		state = state + " "
	}
	identity := fmt.Sprintf("function %v", rawName)
	if funType == Fallback {
		identity = "fallback"
	} else if funType == Receive {
		identity = "receive"
	} else if funType == Constructor {
		identity = "constructor"
	}
	str := fmt.Sprintf("%v(%v) %sreturns(%v)", identity, strings.Join(inputNames, ", "), state, strings.Join(outputNames, ", "))

	return Method{
		Name:            name,
		RawName:         rawName,
		Type:            funType,
		StateMutability: mutability,
		Constant:        isConst,
		Payable:         isPayable,
		Inputs:          inputs,
		Outputs:         outputs,
		str:             str,
		Sig:             sig,
		ID:              id,
	}
}

func (method Method) String() string {
	return method.str
}

// IsConstant returns the indicator whether the method is read-only.
// IsConstant返回该方法是否为只读的指示符。
func (method Method) IsConstant() bool {
	return method.StateMutability == "view" || method.StateMutability == "pure" || method.Constant
}

// IsPayable returns the indicator whether the method can process
// plain ether transfers.
// IsPayable返回该方法是否可以处理纯以太传输的指标。
func (method Method) IsPayable() bool {
	return method.StateMutability == "payable" || method.Payable
}