// Overlapped.cpp : 定义控制台应用程序的入口点。

#include "stdafx.h"

#include <windows.h>

#include <iostream>

using namespace std;

VOID CALLBACK CompletionRoutine(

_In_ DWORD ErrorCode,

_In_ DWORD ReturnLength,

_Inout_ LPOVERLAPPED Overlapped);

HANDLE __FileHandle = NULL;

char __BufferData[20] = {0};

int main()

{

BOOL IsOk = FALSE;

OVERLAPPED Overlapped = { 0 };

__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;

}

//通知IO有异步IO和Overlapped的设置，读四个字节每次

//不用等待是因为没有创建事件当然不用搞

//OverLapped这里的作用是利用Overlapped->Offset 往下加字节设置位置读取字节

IsOk = ReadFileEx(__FileHandle, __BufferData, 4,&Overlapped,

(LPOVERLAPPED_COMPLETION_ROUTINE)CompletionRoutine);

if (IsOk == FALSE)

{

int LastError = GetLastError();

if (LastError == ERROR_IO_PENDING)

{

}

}

Exit:

SleepEx(0,TRUE);//只有为TRUE时候，等待完成历程返回时退出

if (__FileHandle != NULL)

{

CloseHandle(__FileHandle);

__FileHandle = NULL;

}

printf("Input AnyKey To Exit\r\n");

getchar();

return 0;

}

VOID CALLBACK CompletionRoutine(

_In_ DWORD ErrorCode,

_In_ DWORD ReturnLength,

_Inout_ LPOVERLAPPED Overlapped

)

{

if (ErrorCode == ERROR_SUCCESS)

{

int i = 0;

for (i = 0; i < ReturnLength; i++)

{

printf("%c", __BufferData[i]);

}

Overlapped->Offset += ReturnLength;//

ReadFileEx(__FileHandle, __BufferData, 4, Overlapped,

(LPOVERLAPPED_COMPLETION_ROUTINE)CompletionRoutine);

}

else if (ErrorCode==ERROR_HANDLE_EOF)

{

//数据完成

printf("\r\n");

GetFileSize

}

else

{

}

}