# Intel's C++ Asynchronous I/O Library for Windows* Operating Systems

This topic only applies to Windows* OS.

Intel's C/C++ asynchronous I/O (AIO) library implementation for the Windows operating system (on IA-32 (C++ only; does not pertain to DPC++) and Intel® 64 platforms) is similar to the POSIX* AIO library implementation for the Linux* operating system.

The differences between Intel's C/C++ AIO Windows OS implementation and the standard POSIX AIO implementation are listed below:

- In struct aiocb,
  - The Windows OS compatible type `HANDLE` replaces the POSIX AIO type `unsigned int` for the file descriptor `aio_fildes.`

  - The type `intptr_t` replaces the POSIX AIO types `ssize_t` and `__off_t`.

- The structure specifying the signal event descriptor, struct sigevent is similar to the Linux* operating system implementation of the POSIX AIO library. It differs from the Linux* implementation in the following ways:
  - Signal notification and non-notification for thread call-back is supported
  - Signal notification on completion of the AIO operation is not supported

    This is true for programs that were already written for Linux/Unix and ported to Windows OS that wish to setup an AIO completion handler without the name of the handler set in the `aiocb struct`. Because of the way that signals are supported in Windows, this is impossible to implement. For new applications, or to port existing applications, the programmer should set the name of the handler before calling the `aio_read` or `aio_write` routines. For example:

        static void aio_CompletionRoutine(sigval_t sigval)
        {
            // … code …
        }

        … code …

        my_aio.aio_sigevent.sigev_notify          = SIGEV_THREAD;
        my_aio.aio_sigevent.sigev_notify_function = aio_CompletionRoutine;

### Note

The POSIX AIO library and the Microsoft* SDK provide similar AIO functions. The main difference between the POSIX AIO functions and the Windows operating system-based AIO functions is that while POSIX allows you to execute AIO operations with any file, the Windows operating system executes AIO operations only with files flagged with FILE_FLAG_OVERLAPPED.

Intel's asynchronous I/O library functions listed below are all based on POSIX AIO functions. They are defined in the aio.h file.

- aio_read()
- aio_write()
- aio_suspend()
- aio_error()
- aio_return()
- aio_fsync()
- aio_cancel()
- lio_listio()

Parent topic: Intel's C++ Asynchronous I/O Extensions for Windows* Operating Systems

- aio_read
  Performs an asynchronous read operation.
- aio_write
  Performs an asynchronous write operation.
- Example for aio_read and aio_write Functions
- aio_suspend
  Suspends the calling process until one of the asynchronous I/O operations completes.
- Example for aio_suspend Function
- aio_error
  Returns error status for asynchronous I/O requests.
- aio_return
  Returns the final return status for the asynchronous I/O request.
- Example for aio_error and aio_return Functions
- aio_fsync
  Synchronizes all outstanding asynchronous I/O operations.
- aio_cancel
  Cancels outstanding asynchronous I/O requests for the file descriptor fd.
- Example for aio_cancel Function
- lio_listio
  Performs an asynchronous read operation.
- Example for lio_listio Function
- Handling Errors Caused by Asynchronous I/O Functions