作者:手机用户2502915433 | 来源:互联网 | 2023-07-04 12:12
// Copyright 2013 . All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef _DEFER_H_
#define _DEFER_H_
#include
#include
//
// 需要支持C11 -std=c++11
// defer 语句定义一个延迟执行闭包函数的对象
//
// 基于用法:
//
// FILE* fp = fopen("foo.txt", "rt");
// if(fp == NULL) return false;
// defer([&](){ printf("fclose(fp)\n"); fclose(fp); });
//
// char* buf = new char[1024];
// defer([&](){ printf("delete buf\n"); delete[] buf; });
//
// defer([](){ printf("defer a: %d\n", __LINE__); });
// defer([](){ printf("defer a: %d\n", __LINE__); });
// defer([](){ printf("defer a: %d\n", __LINE__); });
//
// {
// defer([](){ printf("defer b: %d\n", __LINE__); });
// defer([](){ printf("defer b: %d\n", __LINE__); });
// defer([](){ printf("defer b: %d\n", __LINE__); });
// }
//
// defer([](){
// printf("defer c:\n");
// for(int i = 0; i <3; ++i) {
// defer([&](){ defer([&](){
// printf("\ti = %d: begin\n", i);
// defer([&](){ printf("\ti = %d\n", i); });
// printf("\ti = %d: end\n", i);
// });});
// }
// });
//
// 注意事项:
//
// 1. defer 定义的对象在超出作用域时执行闭包函数(析构函数)
// 2. defer 定义的对象在同一个文件内部标识符不同(根据行号生成)
// 3. defer 在全局作用域使用可能会出现重名现象(行号相同)
// 4. defer 在判断语句使用可能提前执行(作用域结束时)
// 5. defer 在循环语句内使用无效(作用域结束时)
// 6. defer 和Go语言的defer并不完全等价
//
// 更多参考:
//
// http://blog.korfuri.fr/post/go-defer-in-cpp/
// http://blog.korfuri.fr/attachments/go-defer-in-cpp/defer.hh
// http://blogs.msdn.com/b/vcblog/archive/2011/09/12/10209291.aspx
// http://golang.org/doc/effective_go.html#defer
// http://golang.org/ref/spec#Defer_statements
//
#define defer _DEFER_ACTION_MAKE /* ([&](){ ... }); */
// auto _defer_action_line???_ = _DeferredActionCtor([&](){ ... })
#define _DEFER_ACTION_MAKE auto \
_DEFER_ACTION_VAR(_defer_action_line, __LINE__, _) = _DeferredActionCtor
#define _DEFER_ACTION_VAR(a, b, c) _DEFER_TOKEN_CONNECT(a, b, c)
#define _DEFER_TOKEN_CONNECT(a, b, c) a ## b ## c
// 持有闭包函数
class _DeferredAction {
private:
std::function func_;
template
friend _DeferredAction _DeferredActionCtor(T&& p);
template
_DeferredAction(T&& p): func_(std::bind(std::forward(p))) {
std::cout <<"NEW 1" <>(other.func_)) {
other.func_ = nullptr;
std::cout <<"NEW 2" <
_DeferredAction _DeferredActionCtor(T&& p) {
return _DeferredAction(std::forward(p));
}
#endif // _DEFER_H_
测试:
/*
* File: main.cpp
* Author: Vicky.H
* Email: eclipser@163.com
*/
#include "defer.h"
#include
void sayHello(const char* name) {
printf("hello %s\n", name);
}
void funTest() {
printf("funTest 1\n");
defer([]() {
printf("defer c: %d\n", __LINE__); });
defer([]() {
printf("defer c: %d\n", __LINE__); });
defer([]() {
printf("defer c: %d\n", __LINE__); });
printf("funTest 2\n");
}
/*
*
*/
int main(void) {
defer([]() {
printf("defer a: %d\n", __LINE__); });
defer([]() {
printf("defer a: %d\n", __LINE__); });
defer([]() {
printf("defer a: %d\n", __LINE__); });
defer([](){
sayHello("jack"); });
{
defer([](){ printf("defer b: %d\n", __LINE__); });
defer([](){ printf("defer b: %d\n", __LINE__); });
defer([](){ printf("defer b: %d\n", __LINE__); });
std::cout <<"in code scope" <
git: http://git.oschina.net/eclipser/defer4cpp.git
注意,以上代码需要支持C++11 : -std=c++11
输出:
NEW 1
NEW 1
NEW 1
NEW 1
NEW 1
NEW 1
NEW 1
in code scope
defer b: 42
DELETE
defer b: 41
DELETE
defer b: 40
DELETE
---------------------------
Done 1
Done 2
Done 3
---------------------------
funTest 1
NEW 1
NEW 1
NEW 1
funTest 2
defer c: 22
DELETE
defer c: 20
DELETE
defer c: 18
DELETE
hello jack
DELETE
defer a: 35
DELETE
defer a: 33
DELETE
defer a: 31
DELETE
运行 FINISHED; 退出值0; 实时: 20ms; 用户: 0ms; 系统: 0ms