Windows 非同步IO和 完成連接埠（IOCP）

 

見過網上好多的完成連接埠和網路通訊的文章，呵呵，這裡就簡單的說說檔案非同步IO和完成連接埠，這裡僅僅說說讀取操作。下面是一些總結，很少有人提及，認真的看過MSDN文檔之後得出的，歡迎指正。

1. 要對檔案非同步IO操作，需要在檔案建立的時候指定FILE_FLAG_OVERLAPPED屬性的；
2. 非同步ReadFileEx是不能讀取和IO完成連接埠綁定的檔案控制代碼的；
3. 非同步ReadFileEx對OVERLAPPED的hEvent忽視；
4. 非同步完成後可以出發回調，回調介面需要指定WINAPI屬性，實際上就是_stdcall，如果不指定則預設是_cdecl屬性，回調完成後，會崩潰的；
5. 最後需要等待。

這裡簡單的附上一段非同步代碼：

 

#include <process.h>#include <Windows.h>VOID WINAPI rt(  __in     DWORD dwErrorCode,  __in     DWORD dwNumberOfBytesTransfered,  __inout  LPOVERLAPPED lpOverlapped){    printf("rt call back\n");}int _tmain(int argc, _TCHAR* argv[]){    OVERLAPPED *ol = new OVERLAPPED;    memset(ol, 0, sizeof *ol);    HANDLE file = CreateFile("ReadMe.txt",         GENERIC_READ,         0,         NULL,         OPEN_EXISTING ,         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED ,        NULL);    if(file == INVALID_HANDLE_VALUE)    {        goto mem_free1;    }    size_t buf_len = 1024;    char *buf = new char[buf_len];    if(!buf)    {        goto mem_free1;    }    if(!ReadFileEx(file, buf, buf_len, ol, rt))    {        goto mem_free;    }    SleepEx(INFINITE, TRUE);mem_free:    delete []buf;mem_free1:    delete ol;        CloseHandle(file);return 0;}

 

對於ReadFile，主線程在觸發非同步作業之後，就需要有另外的線程來做輔助工作，可以使用event事件，這裡主要介紹完成連接埠，沒有多少好說的，也貼上代碼吧：

 

#include <process.h>#include <windows.h>//建立一個IO完成連接埠HANDLE CreateNewCompletionPort(DWORD dwNumberOfConcurrentThreads){    return( CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, NULL, dwNumberOfConcurrentThreads));}//將裝置與完成連接埠管理起來BOOL AssociateDeviceWithCompletionPort(HANDLE hCompletionPort, HANDLE hDevice,  DWORD dwCompletionKey) {    HANDLE h = CreateIoCompletionPort(hDevice,   hCompletionPort, dwCompletionKey,   0);    return (h == hCompletionPort);}void reader(void *in){    HANDLE     port    = (HANDLE)in;    DWORD      rcv_len = 0;    ULONG_PTR  my_key  = 0;    OVERLAPPED *ol1    = NULL;    while(1)    {        if(!GetQueuedCompletionStatus(port, &rcv_len, &my_key, &ol1, INFINITE))        {            int err = GetLastError();            continue;        }        else        {            _endthread();        }    }}int _tmain(int argc, _TCHAR* argv[]){    int key = 12345;    HANDLE port = CreateNewCompletionPort(4);    if(!port)    {        int err = GetLastError();        return 0;    }    HANDLE file = CreateFile("ReadMe.txt",         GENERIC_READ,         0,         NULL,         OPEN_EXISTING ,         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED ,        NULL);    if(file == INVALID_HANDLE_VALUE)    {        CloseHandle(port);    }    OVERLAPPED *ol = new OVERLAPPED;    memset(ol, 0, sizeof *ol);        if(!AssociateDeviceWithCompletionPort(port, file, key))    {        int err = GetLastError();        CloseHandle(port);        CloseHandle(file);        delete ol;        return 0;    }    int buf_len = 1000;    char *buf = new char[buf_len];    if(!buf)    {        CloseHandle(port);        CloseHandle(file);        delete ol;        return 0;    }    HANDLE h_thread = (HANDLE)_beginthread(reader, 0, port);    if(!ReadFile(file, buf, buf_len, NULL, ol))    {        int err = GetLastError();        if(err != ERROR_IO_PENDING)        {            CloseHandle(port);            CloseHandle(file);            delete ol;            WaitForSingleObject(h_thread, INFINITE);            return 0;        }    }    WaitForSingleObject(h_thread, INFINITE);    CloseHandle(port);    CloseHandle(file);    delete ol;    delete []buf;    return 0;}