[C++知识库]C++文件操作

// test.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//

#include <iostream>
#include <fstream>
#include <mutex>
#include <map>
#include <string>
#include <filesystem>

//文件管理单例类
class ManagerFile
{
public:
	static ManagerFile& getInstance()
	{
		static std::once_flag s_flag;
		std::call_once(s_flag, [&]() {
			instance_.reset(new ManagerFile());
			});

		return *instance_;
	}

	//
	//************************************
	// FullName:   ManagerFile::init
	// Access:     public 
	// @Parameter: std::string name	   文件名
	// @Parameter: size_t fileMaxSize  文件大小限制
	// @Returns:   void
	// @author:    君莫笑
	// @date:      2021/10/26 15:07
	// @bref:      初始化
	//************************************
	void init(std::string name, size_t fileMaxSize);					

	//************************************
	// FullName:   ManagerFile::writeFile
	// Access:     public 
	// @Parameter: std::string name   文件名
	// @Parameter: const char * fp    写入文件的内容
	// @Parameter: const int len      写入数据长度
	// @Returns:   void
	// @author:    君莫笑
	// @date:      2021/10/26 15:08
	// @bref:      写入数据
	//************************************
	void writeFile(std::string name, const char* fp, const int len);

	//************************************
	// FullName:   ManagerFile::removeFile
	// Access:     public 
	// @Parameter: std::string name    文件名
	// @Returns:   bool
	// @author:    君莫笑
	// @date:      2021/10/26 15:09
	// @bref:      删除文件
	//************************************
	bool removeFile(std::string name);

private:
	ManagerFile() = default;

	//防止拷贝构造
	ManagerFile& operator=(const ManagerFile&) = delete;
	ManagerFile(const ManagerFile& data) = delete;
	static std::unique_ptr<ManagerFile> instance_;

private:
	std::map<std::string, std::shared_ptr<std::ofstream>> m_foutMap;
	std::map<std::string, size_t> m_currentFileSizeMap;
	size_t m_iFileMaxSize{ 0 };
	size_t m_iWriteFileMode{ 0 };
	std::mutex m_fileOpt_mx;
};

std::unique_ptr<ManagerFile> ManagerFile::instance_;

void ManagerFile::init(std::string name, size_t fileMaxSize)
{
	std::lock_guard<std::mutex> lck(m_fileOpt_mx);
	m_iFileMaxSize = fileMaxSize;
	auto itemPos = m_foutMap.find(name);
	if (itemPos != m_foutMap.end())
	{
		if (!itemPos->second)
		{
			itemPos->second.reset(new std::ofstream());
		}
	}
	else
	{
		m_foutMap[name].reset(new std::ofstream());
	}

	if (m_foutMap[name])
	{
		std::string strFileName = makeFilePathName(name);
		if (!strFileName.empty())
		{
			m_foutMap[name]->open(strFileName, std::ios::binary | std::ios::out | std::ios::trunc);
			m_currentFileSizeMap[name] = 0;	
		}
	}
}

void ManagerFile::writeFile(std::string name, const char* fp, const int len)
{
	std::lock_guard<std::mutex> lck(m_fileOpt_mx);
	auto itemPos = m_foutMap.find(name);
	if (itemPos == m_foutMap.end())
	{
		return;
	}

	if (!itemPos->second)
	{
		return;
	}

	int iCurrFileSize = 0;
	auto itr = m_currentFileSizeMap.find(name);
	if (itr == m_currentFileSizeMap.end())
	{
		return;
	}

	iCurrFileSize = itr->second;
	std::string strFileName = makeFilePathName(name);
	if (iCurrFileSize < m_iFileMaxSize)
	{
		itemPos->second->write(fp, len);
		itemPos->second->flush();
		std::filesystem::path p(strFileName);
		itr->second = std::filesystem::file_size(p);
	}
	else
	{
		itemPos->second->flush();
		itemPos->second->close();
		itr->second = 0;
		
		if (!strFileName.empty())
		{
			itemPos->second->open(strFileName, std::ios::binary | std::ios::out | std::ios::trunc);
		}
	}
}


bool ManagerFile::removeFile(std::string name)
{
	std::lock_guard<std::mutex> lck(m_fileOpt_mx);
	auto itemPos = m_foutMap.find(name);
	if (itemPos == m_foutMap.end())
	{
		return false;
	}

	if (!itemPos->second)
	{
		return false;
	}

	if (itemPos->second->is_open())
	{
		itemPos->second->flush();
		itemPos->second->close();
	}

	bool bl = false;

	std::string strFileName = makeFilePathName(name);
	if (!strFileName.empty())
	{
		std::ifstream fileTemp(strFileName.c_str());
		itemPos->second->open(strFileName, std::ios::binary | std::ios::out | std::ios::trunc);		//清空文件内容
		itemPos->second->flush();
		itemPos->second->close();
		std::this_thread::sleep_for(std::chrono::milliseconds(100));			//必须要等待，否则可能会删除文件失败
		bool bl = remove(strFileName.c_str());
	}

	if (itemPos->second && itemPos->second->is_open())
	{
		itemPos->second->close();
		itemPos->second = nullptr;
	}

	m_foutMap.erase(itemPos);
	return bl;
}

std::string ManagerFile::makeFilePathName(std::string& name)
{
	std::filesystem::path pDir= std::filesystem::current_path();
	std::string fileName = pDir.string();
	fileName += "\\";
	fileName += name;
	return fileName;
}


int main()
{
	//使用实例
	std::string strFileName = "123.txt";
	std::string strData = "test file 12345678";
	size_t iFileSize = 1024;
	ManagerFile::getInstance().init("123.txt", iFileSize);
	ManagerFile::getInstance().writeFile("123.txt", strData.c_str(), strData.length());
	return 0;
}