自定义HID的异步操作示例

自定义HID的异步操作和同步类似，这里有两个关键的区别：

• 第一：CreateFile时wFlagsAndAttributes参数包括FILE_FLAG_OVERLAPPED标识。
• 第二：ReadFile,WriteFile必须的OVERLAPPED参数；

异步CreateFile打开HID示例：

 HANDLE tmp_DeviceHandle = CreateFile(  strDevicePath,
                                         GENERIC_READ | GENERIC_WRITE,
                                         FILE_SHARE_READ | FILE_SHARE_WRITE,
                                         NULL, 
                                         OPEN_EXISTING,
                                         FILE_FLAG_OVERLAPPEDm//和同步的FILE_ATTRIBUTE_NORMAL参数不一样
                                         NULL);
        if (tmp_DeviceHandle == INVALID_HANDLE_VALUE)
        {
            CloseHandle(tmp_DeviceHandle);
            continue;
        }

异步ReadFile从自定义HID读数据

以下内容为截取并整理github hidapi的代码片段，详见：HidApi库来进行开发，下载地址是https://github.com/yigityuce/HidApi

 OVERLAPPED ol;
 memset(&ol, 0, sizeof(ol));
 ol.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
 isok = ReadFile(tmp_DeviceHandle, data, 64, &rtn, NULL);
 if (!isok)
 {
    if (GetLastError() != ERROR_IO_PENDING) 
    {
        /* ReadFile() has failed.
           Clean up and return error. */
        CancelIo(dev->device_handle);
        dev->read_pending = FALSE;
        goto end_of_function;
    }
    else
    {
        res = WaitForSingleObject(ol.hEvent, 500);
        if (res != WAIT_OBJECT_0)
        {
            /* There was no data this time. Return zero bytes available,
               but leave the Overlapped I/O running. */
            return 0;
        }
        res = GetOverlappedResult(tmp_DeviceHandle, &ol, &rtn, TRUE/*wait*/);
    }
 }

异步WritelFile写数据到自定义HID

以下内容为截取并整理github hidapi的代码片段，详见：HidApi库来进行开发，下载地址是https://github.com/yigityuce/HidApi

 OVERLAPPED ol;
 memset(&ol, 0, sizeof(ol));
 ol.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
 isok = WritleFile(tmp_DeviceHandle, data, 64, &rtn, NULL);
 if (!isok)
 {
    if (GetLastError() != ERROR_IO_PENDING) 
    {

    }
    else
    {
        res = WaitForSingleObject(ol.hEvent, 500);
        if (res != WAIT_OBJECT_0)
        {
            /* There was no data this time. Return zero bytes available,
               but leave the Overlapped I/O running. */
            return 0;
        }

    }
 }