异步读写(ReadFileEx和ReadFile)之overlapped
原文: https://www.cnblogs.com/L-Sunny/p/8389388.html#include "stdafx.h"
#include <windows.h>
#include <iostream>
using namespace std;
#define PAGE_SIZE 0x1000
void Sub_1(); //ReadFile 异步操作
void Sub_2(); //ReadFileEx
DWORD WINAPI Sub_1ThreadProcedure(LPVOID ParameterData);
DWORD WINAPI Sub_2ThreadProcedure(LPVOID ParameterData);
OVERLAPPED __Overlapped = { 0 };
char __BufferData = {0};
int main()
{
Sub_1();
//Sub_2();
}
void Sub_1()
{
BOOL IsOk = FALSE;
DWORD ReturnLength = 0;
HANDLE FileHandle = CreateFile(L"ReadMe.txt", GENERIC_ALL, FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL); //FILE_FLAG_OVERLAPPED 很重要在异步
//有FILE_FLAG_OVERLAPPED系统就已经默认OverLapped了如果要同步必须删除
if (FileHandle == INVALID_HANDLE_VALUE)
{
int LastError = GetLastError();
goto Exit;
}
__Overlapped.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL); //绝对要创建 IRP那里看
if (__BufferData == NULL)
{
goto Exit;
}
IsOk = ReadFile(FileHandle, __BufferData, 4, &ReturnLength, &__Overlapped); //这里是通知IO要进行异步__Overlapped
//接下来返回到线程，所以有Wait那一步，线程才会去执行 线程和当前进程无关
if (IsOk == FALSE)
{
int LastError = GetLastError();
if (LastError == ERROR_IO_PENDING)
{
printf("ERROR_IO_PENDING\r\n");
}
}
HANDLE ThreadHandle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Sub_1ThreadProcedure,
(LPVOID)FileHandle, 0, NULL);
WaitForSingleObject(ThreadHandle, INFINITE);
Exit:
if (FileHandle != NULL)
{
CloseHandle(FileHandle);
FileHandle = NULL;
}
printf("\r\n");
return;
}
DWORD WINAPI Sub_1ThreadProcedure(LPVOID ParameterData)
{
HANDLE FileHandle = (HANDLE)ParameterData;
BOOL IsOk = FALSE;
DWORD ReturnLength = 0;
while (1)
{
IsOk = WaitForSingleObject(__Overlapped.hEvent, INFINITE);
IsOk -= WAIT_OBJECT_0;
if (IsOk == 0)
{
IsOk = GetOverlappedResult(FileHandle, &__Overlapped, &ReturnLength, INFINITE);//ReturnLength读了多少字节
if (IsOk==TRUE)
{
int i = 0;
for (i = 0; i < ReturnLength; i++)
{
printf("%c", __BufferData);
}
__Overlapped.Offset += ReturnLength;//这里是每次读写的起始位置，所以要加下去
ReadFile(FileHandle, &__BufferData, 4, &ReturnLength, &__Overlapped);
}
else
{
//数据完毕
break;
}
}
else
{
return 0;
}
}
return 0;
}
void Sub_2()
{
BOOL IsOk = FALSE;
HANDLE FileHandle = CreateFile(L"ReadMe.txt", GENERIC_ALL, FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
if (FileHandle == INVALID_HANDLE_VALUE)
{
int LastError = GetLastError();
goto Exit;
}
//__Overlapped.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL); //绝对不能提供该事件
HANDLE ThreadHandle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Sub_2ThreadProcedure,
(LPVOID)FileHandle, 0, NULL);
if (__BufferData == NULL)
{
goto Exit;
}
IsOk = ReadFileEx(FileHandle, __BufferData, 4, &__Overlapped, NULL);
if (IsOk == FALSE)
{
int LastError = GetLastError();
if (LastError == ERROR_IO_PENDING)
{
//成功
}
}
WaitForSingleObject(ThreadHandle, INFINITE);
Exit:
if (FileHandle != NULL)
{
CloseHandle(FileHandle);
FileHandle = NULL;
}
printf("\r\n");
return;
}
DWORD WINAPI Sub_2ThreadProcedure(LPVOID ParameterData)
{
HANDLE FileHandle = (HANDLE)ParameterData;
DWORD ReturnLength = 0;
BOOL IsOk = FALSE;
while (1)
{
/*如果函数调用返回FALSE则可以用GetLastError来得到错误，如果返回成功则可以通过
lpNumberOfBytesTransferred参数来确定当前有多少数据已经被读或写。lpOverlapped
参数必须与调用ReadFile或WriteFile时使用同一个数据区。最后一个参数bWait表明是
否等待异步操作结束时才返回，如果设置为TRUE就可以等待文件读写完成时返回，
否则就会马上返回，利用这个特点可以利用它来等待异步文件操作的结束
（就如同等待事件变为有信号状态一样起到相同的作用）。
*/
IsOk = GetOverlappedResult(FileHandle, &__Overlapped, &ReturnLength, TRUE);
//IsOk = WaitForSingleObject(__Overlapped.hEvent, INFINITE); //?? 绝对不能这样做
if (IsOk == TRUE)
{
int i = 0;
for (i = 0; i < ReturnLength; i++)
{
printf("%c", __BufferData);
}
__Overlapped.Offset += ReturnLength;
ReadFileEx(FileHandle, &__BufferData, 4, &__Overlapped, NULL);
}
else
{
return 0;
}
}
return 0;
}
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