C++线程的用法《C++多线程编程实战》

最新推荐文章于 2025-06-20 11:02:22 发布

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最新推荐文章于 2025-06-20 11:02:22 发布

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分类专栏： C++ 文章标签： VS2017 C++

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本文介绍了一个CMySQL类的实现，用于连接MySQL数据库，执行读写操作，并通过多线程进行数据库测试。该类使用单例模式管理实例，并提供了连接、断开连接、读取数据和写入数据的方法。

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需要安装MySQL C Connector

CMYSQL.h

#include "pch.h"
#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>

class CMySQL
{
public:
	static CMySQL* CreateInstance(char* szHostName, char* szDatabase,
		char* szUserId, char* szPassword);
	static void ReleaseInstance();
	bool ConnectInstance();
	bool DisconnectInstance();
	bool ReadData(char* szQuery, char* szResult, size_t uBufferLenght);
	bool WriteData(char* szQuery, char* szResult, size_t uBufferLenght);
private:
	CMySQL(char* szHostName, char* szDatabase, char* szUserId, char*
		szPassword);
	~CMySQL();
	char* szHostName;
	char* szDatabase;
	char* szUserId;
	char* szPassword;
	MYSQL* mysqlConnection;
	static CMySQL* mySqlInstance;
};

CMYSQL.cpp

#include "pch.h"
#include "CMYSQL.h"
#include <string>

CMySQL* CMySQL::mySqlInstance = NULL;
CMySQL* CMySQL::CreateInstance(char* szHostName, char* szDatabase,
	char* szUserId, char* szPassword)
{
	if (mySqlInstance)
	{
		return mySqlInstance;
	}
	return new CMySQL(szHostName, szDatabase, szUserId, szPassword);
}
void CMySQL::ReleaseInstance()
{
	if (mySqlInstance)
	{
		delete mySqlInstance;
	}
}

CMySQL::CMySQL(char* szHostName, char* szDatabase, char*szUserId,
	char* szPassword)
{
	size_t length = 0;
	this->szHostName = new char[length = strlen(szHostName) + 1];
	strcpy_s(this->szHostName, length, szHostName);
	this->szDatabase = new char[length = strlen(szDatabase) + 1];
	strcpy_s(this->szDatabase, length, szDatabase);
	this->szUserId = new char[length = strlen(szUserId) + 1];
	strcpy_s(this->szUserId, length, szUserId);

	this->szPassword = new char[length = strlen(szPassword) + 1];
	strcpy_s(this->szPassword, length, szPassword);
}

CMySQL::~CMySQL()
{
	delete szHostName;
	delete szDatabase;
	delete szUserId;
	delete szPassword;
}

bool CMySQL::ConnectInstance()
{
	MYSQL* mysqlLink = NULL;

	try
	{
		mysqlConnection = mysql_init(NULL);
		mysqlLink = mysql_real_connect(mysqlConnection, szHostName,
			szUserId, szPassword, szDatabase, 3306, NULL, 0);
	}
	catch (...)
	{
		mysqlConnection = 0;
		return false;
	}
	return mysqlLink ? true : false;
}

bool CMySQL::DisconnectInstance()
{
	try
	{
		mysql_close(mysqlConnection);
		return true;
	}
	catch (...)
	{
		return false;
	}
}

bool CMySQL::ReadData(char* szQuery, char* szResult, size_t uBufferLenght)
{
	int mysqlStatus = 0;
	MYSQL_RES* mysqlResult = NULL;
	MYSQL_ROW mysqlRow = NULL;
	my_ulonglong numRows = 0;
	unsigned numFields = 0;
	try
	{
		mysqlStatus = mysql_query(mysqlConnection, szQuery);
		if (mysqlStatus)
		{
			return false;
		}
		else
		{
			mysqlResult = mysql_store_result(mysqlConnection);
		}
		if (mysqlResult)
		{
			numRow = mysql_num_rows(mysqlResult);
			numFields = mysql_num_fields(mysqlResult);
		}
		mysqlRow = mysql_fetch_row(mysqlResult);
		if (mysqlRow)
		{
			if (!mysqlRow[0])
			{
				mysql_free_result(mysqlResult);
				return false;
			}
		}
		else
		{
			mysql_free_result(mysqlResult);
			return false;
		}

		size_t szResultLength = strlen(mysqlRow[0]) + 1;
		strcpy_s(szResult, szResultLength > uBufferLenght ?
			uBufferLenght : szResultLength, mysqlRow[0]);

		if (mysqlResult)
		{
			mysql_free_result(mysqlResult);
			mysqlResult = NULL;
		}
	}
	catch (...)
	{
		return false;
	}
	return true;
}

bool CMySQL::WriteData(char* szQuery, char* szResult, size_t
	uBufferLenght)
{
	try
	{
		int mysqlStatus = mysql_query(mysqlConnection, szQuery);
		if (mysqlStatus)
		{
			size_t szResultLength = strlen("Failed!") + 1;
			strcpy_s(szResult, szResultLength > uBufferLenght ?
				uBufferLenght : szResultLength, "Failed!");
			return false;
		}
	}
	catch (...)
	{
		size_t szResultLength = strlen("Exception!") + 1;
		strcpy_s(szResult, szResultLength > uBufferLenght ?
			uBufferLenght : szResultLength, "Exception!");
		return false;
	}

	size_t szResultLength = strlen("Success") + 1;
	strcpy_s(szResult, szResultLength > uBufferLenght ?
		uBufferLenght : szResultLength, "Success");
	return true;
}

MultithreadedDBTest.cpp

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

#include "pch.h"
#include "CMYSQL.h"
#include <windows.h>

#define BLOCK_SIZE 4096
#define THREADS_NUMBER 3

typedef struct
{
	char szQuery[BLOCK_SIZE];
	char szResult[BLOCK_SIZE];
	bool bIsRead;
} QUERYDATA, *PQUERYDATA;

CRITICAL_SECTION cs;
CMySQL* mySqlInstance = NULL;

DWORD WINAPI StartAddress(LPVOID lpParameter)
{
	PQUERYDATA pQueryData = (PQUERYDATA)lpParameter;
	EnterCriticalSection(&cs);
	if (mySqlInstance->ConnectInstance())
	{
		if (pQueryData->bIsRead)
		{
			memset(pQueryData->szResult, 0, BLOCK_SIZE - 1);
			mySqlInstance->ReadData(pQueryData->szQuery,
				pQueryData->szResult, BLOCK_SIZE - 1);
		}
		else
		{
			mySqlInstance->WriteData(pQueryData->szQuery,
				pQueryData->szResult, BLOCK_SIZE - 1);
		}
		mySqlInstance->DisconnectInstance();
	}
	LeaveCriticalSection(&cs);
	return 0L;
}

int main()
{
	InitializeCriticalSection(&cs);
	mySqlInstance = CMySQL::CreateInstance(
		"mysql.services.expert.its.me", "expertit_9790OS",
		"expertit_9790", "$dbpass_1342#");
	if (mySqlInstance)
	{
		HANDLE hThreads[THREADS_NUMBER];
		QUERYDATA queryData[THREADS_NUMBER] =
		{
			{ "select address from clients where id = 3;",
			"", true },
			{ "update clients set name='Merrill & Lynch' where id=2;",
			"", false },
			{ "select name from clients where id = 2;",
			"", true }
		};
		for (int iIndex = 0; iIndex < THREADS_NUMBER; iIndex++)
		{
			hThreads[iIndex] = CreateThread(NULL, 0,
				(LPTHREAD_START_ROUTINE)StartAddress,
				&queryData[iIndex], 0, 0);
		}
		WaitForMultipleObjects(THREADS_NUMBER, hThreads, TRUE, INFINITE);
		for (int iIndex = 0; iIndex < THREADS_NUMBER; iIndex++)
		{
			printf_s("%s\n", queryData[iIndex].szResult);
		}
		CMySQL::ReleaseInstance();
	}
	DeleteCriticalSection(&cs);
    return system("pause"); 
}