在寫一些大型項目的過程中經常需要一些工具函數，例如獲取隨機數、計時器、打印函數、重要常量（如最大值）、信號與槽等，由于每一個工程都自己手動實現一個實在是太傻，我將其總結放入一個文件中。

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utils.h

// Copyright(C), Edward-Elric233
// Author: Edward-Elric233
// Version: 1.0
// Date: 2022/6/27
// Description: 
#ifndef UTILS_H
#define UTILS_H#include "json.hpp"
#include <iostream>
#include <random>
#include <chrono>
#include <fstream>
#include <memory>
#include <mutex>
#include <unordered_map>
#include <functional>namespace edward {constexpr int INF = 0x3f3f3f3f;//extern std::ofstream ofs;inline void print() {std::cout << "\n";
//    ofs << "\n";
}
template<typename T, typename... Args>
void print(T&& first, Args&&... args) {std::cout << first << " ";
//    ofs << first << " ";print(std::forward<Args>(args)...);
}template<typename Iter>
void printArr(Iter begin, Iter end) {while (begin != end) {std::cout << *begin++ << " ";}std::cout << "\n";
}template<typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, const std::pair<T1, T2>& pr) {os << pr.first << " " << pr.second;return os;
}template<typename Container>
void printArr(const Container& container) {for (auto x : container) {std::cout << x << " ";}std::cout << "\n";
}class Random {
public:// random number generator.static std::mt19937 pseudoRandNumGen;static void initRand(int seed) { pseudoRandNumGen = std::mt19937(seed); }   //設置隨機數種子static int fastRand(int lb, int ub) { return (pseudoRandNumGen() % (ub - lb)) + lb; }static int fastRand(int ub) { return pseudoRandNumGen() % ub; }static int rand(int lb, int ub) { return std::uniform_int_distribution<int>(lb, ub - 1)(pseudoRandNumGen); }static int rand(int ub) { return std::uniform_int_distribution<int>(0, ub - 1)(pseudoRandNumGen); }
};class Timer {std::chrono::time_point<std::chrono::system_clock> timePoint_;
public:Timer(): timePoint_(std::chrono::system_clock::now()) {}Timer(const Timer&) = delete;~Timer() = default;void operator() (const std::string& msg) {auto duration = std::chrono::system_clock::now() - timePoint_;print(msg, static_cast<double>(duration.count()) / decltype(duration)::period::den, "s");}void reset() {timePoint_ = std::chrono::system_clock::now();}void operator() (nlohmann::json& arr) {auto duration = std::chrono::system_clock::now() - timePoint_;arr.push_back(duration.count());}};using Slot = std::shared_ptr<void>;//前置聲明
template<typename Signature>
class Signal;
template<typename Ret, typename... Args>
class Signal<Ret(Args...)>;namespace detail {//前置聲明template<typename Callback> class SlotImpl;template<typename Callback>class SignalImpl {public:using SlotList = std::unordered_map<SlotImpl<Callback> *, std::weak_ptr<SlotImpl<Callback>>>;SignalImpl(): slots_(new SlotList), mutex_() {}~SignalImpl() {}//只能在加鎖后使用void cowWithLock() {if (!slots_.unique()) {slots_.reset(new SlotList(*slots_));}}//添加槽函數void add(const std::shared_ptr<SlotImpl<Callback>> &slot) {std::lock_guard<std::mutex> lockGuard(mutex_);cowWithLock();slots_->insert({slot.get(), slot});}//供SlotImpl調用，刪除槽函數void remove(SlotImpl<Callback> *slot) {std::lock_guard<std::mutex> lockGuard(mutex_);cowWithLock();slots_->erase(slot);}std::shared_ptr<SlotList> getSlotList() {std::lock_guard<std::mutex> lockGuard(mutex_);return slots_;}private:std::mutex mutex_;//保存SlotImpl的weak_ptr//之所以不保存SlotList而是保存其shared_ptr是為了實現COWstd::shared_ptr<SlotList> slots_;};template<typename Callback>class SlotImpl {public:SlotImpl(Callback&& cb, const std::shared_ptr<SignalImpl<Callback>> &signal): cb_(cb), signal_(signal) {}~SlotImpl() {auto signal = signal_.lock();if (signal) {signal->remove(this);}}Callback cb_;private://保存SignalImpl的weak_ptrstd::weak_ptr<SignalImpl<Callback>> signal_;};
}template<typename Ret, typename... Args>
class Signal<Ret(Args...)> {
public:using Callback = std::function<Ret(Args...)>;using SignalImpl = detail::SignalImpl<Callback>;using SlotImpl = detail::SlotImpl<Callback>;Signal(): impl_(new SignalImpl) {}~Signal() {}/*!* 添加槽函數* @param cb 槽函數* @return 需要保存這個智能指針，否則會自動從槽函數列表中刪除*/template<typename Func>Slot connect(Func&& cb) {std::shared_ptr<SlotImpl> slot(new SlotImpl(std::forward<Func>(cb), impl_));impl_->add(slot);return slot;}template<typename ...ARGS>void operator() (ARGS&&... args) {auto slots = impl_->getSlotList();//使用引用避免智能指針的解引用auto &s = *slots;for (auto &&[pSlotImpl, pWkSlotImpl] : s) {auto pShrSlotImpl = pWkSlotImpl.lock();if (pShrSlotImpl) {pShrSlotImpl->cb_(std::forward<ARGS>(args)...);}}}private://保存shared_ptr的原因是需要傳遞給SlotImpl，在SlotImpl析構的時候會清除自己const std::shared_ptr<SignalImpl> impl_;
};}#endif //UTILS_H

utils.cpp

// Copyright(C), Edward-Elric233
// Author: Edward-Elric233
// Version: 1.0
// Date: 2022/6/27
// Description: 
#include "utils.h"namespace edward {std::mt19937 Random::pseudoRandNumGen(std::chrono::system_clock::now().time_since_epoch().count()); //默認使用當下時間戳初始化隨機數種子，精確到納秒//std::ofstream ofs("../test/debug.txt");}