C++ 批量打开写入文件

用到了C++17的filesystem 库

说明：这个函数主要是用来处理日志中不同Thread的日志，主要目的是将不同Thread的日志写到不同的文件中

int GetThreadTime(const char * INPUT, const char * OutputFolder)
{
	std::map<std::string, std::ofstream> mapWrite;
	std::filesystem::path pth(INPUT);
	if(exists(pth))
	{
		std::cout << INPUT <<"文件存在\n";
	}
	else
	{
		std::cout<< INPUT << "文件不存在\n";
		return 0;
	}

	if (!std::filesystem::exists(OutputFolder))
	{
		std::filesystem::create_directory(OutputFolder);
	}

	fstream fi(INPUT,ios_base::in);
	char buf[2048]{0};
	std::string str;
	char paths[256]{0};
	while (fi.getline(buf,sizeof(buf)))
	{
		str.clear();
		str = buf;
		if (str.find("CalculateDownloadCostTime") != std::string::npos)   //key value
		{
			std::string sthread;
			findThreadId(str,sthread);   //获取Thread ID，string类型
			long stattime,stoptime;
			int costtime;
			getStartTime(str,&stattime,&stoptime,&costtime);   //获取日志行中的参数，本处是开始时间，结束事件，花费时间
			auto result = mapWrite.find(sthread);
			if (result == mapWrite.end())
			{
				sprintf_s(paths,sizeof(paths),"%s%s.txt",OutputFolder,sthread.c_str());
				std::ofstream fo(paths,ios_base::app);
				fo << "threadid    " << sthread << "XXXXXXX logs\n";
				mapWrite.insert(std::pair<std::string, std::ofstream>(sthread,std::move(fo)));  //注意：本处要么用std::move要么用shared_ptr，因为map需要为对象分配内存,而且ofstream也是uncopyable
//http://coliru.stacked-crooked.com/a/c4486879ce9d4db0
//https://stackoverflow.com/questions/42920744/cant-we-manage-stdmapstring-ofstream
			}
			else
			{
				result->second << "threadid    " << sthread << "XXXXXXX logs\n";
			}

		}
		else
		{
			memset(buf,0,sizeof(buf));
			continue;
		}

		memset(buf,0,sizeof(buf));
	}
	for (auto& element : mapWrite)
	{
		element.second.close();        //批量释放句柄
	}
	return 0;
}