IO操作-同步异步

最新推荐文章于 2025-09-27 10:17:33 发布

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这篇博客介绍了如何在Windows环境下使用C++进行文件的同步和异步写入操作。通过`CreateFile`函数创建文件，然后利用`WriteFile`进行同步写入，而异步写入则结合了`OVERLAPPED`结构和`WriteFileEx`函数，配合完成例程实现。示例代码详细展示了同步和两种不同方式的异步写入过程。

// 同步
#include <Windows.h>
#include <stdio.h>

int main()
{
	HANDLE hFile = CreateFile(L"Sync.txt", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hFile == INVALID_HANDLE_VALUE)
	{
		printf("创建文件失败\n");
		return -1;
	}

	DWORD dwWriteBytes = 0;
	BOOL bRet = WriteFile(hFile, L"测试同步文件", sizeof(wchar_t)* wcslen(L"测试同步文件") + 2, &dwWriteBytes, NULL);
	if (bRet == FALSE || dwWriteBytes == 0)
	{
		printf("写入文件失败\n");
	}

	CloseHandle(hFile);

	return 0;
}

// 异步1
#include <Windows.h>
#include <stdio.h>

int main()
{
	OVERLAPPED over = { 0 };
	over.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);

	HANDLE hFile = CreateFile(L"async.txt",
		GENERIC_READ | GENERIC_WRITE,
		FILE_SHARE_READ | FILE_SHARE_WRITE,
		NULL,
		CREATE_ALWAYS,
		FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
		NULL);
	if (hFile == INVALID_HANDLE_VALUE)
	{
		printf("创建文件失败\n");
		return -1;
	}

	DWORD dwWriteBytes = 0;
	BOOL bRet = WriteFile(hFile, L"异步写入文件", sizeof(wchar_t)* wcslen(L"异步写入文件") + 2, &dwWriteBytes, &over);
	if (bRet == FALSE && GetLastError() != ERROR_IO_PENDING)
	{
		printf("写入文件失败\n");
	}

	WaitForSingleObject(over.hEvent, INFINITE);

	CloseHandle(hFile);

	return 0;
}

//异步2
#include <Windows.h>
#include <stdio.h>

// 完成例程
VOID CALLBACK ReadCompleteRoutine(DWORD dwErrorCode, DWORD dwNumberOfBytesWrite, LPOVERLAPPED lpOverlapped);

int main()
{
	OVERLAPPED over = { 0 };
	HANDLE hFile = CreateFile(L"asyncex.txt",
		GENERIC_READ | GENERIC_WRITE,
		FILE_SHARE_READ | FILE_SHARE_WRITE,
		NULL,
		CREATE_ALWAYS,
		FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
		NULL);

	if (INVALID_HANDLE_VALUE == hFile)
	{
		printf("创建文件失败\n");
		return -1;
	}

	DWORD dwWriteBytes = 0;
	BOOL bRet = WriteFileEx(hFile, L"IO异步操作", sizeof(wchar_t)* wcslen(L"IO异步操作") + 2, &over, ReadCompleteRoutine);
	if (bRet == FALSE && GetLastError() != ERROR_IO_PENDING)
	{
		printf("写入文件失败\n");
	}

	SleepEx(10, TRUE);
	CloseHandle(hFile);

	getchar();

	return 0;
}

VOID CALLBACK ReadCompleteRoutine(DWORD dwErrorCode, DWORD dwNumberOfBytesWrite, LPOVERLAPPED lpOverlapped)
{
	printf("写入字节数:%d\n", dwNumberOfBytesWrite);
}