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| <h4 class="subsection">13.10.2 Getting the Status of AIO Operations</h4> |
| |
| <p>As already described in the documentation of the functions in the last |
| section, it must be possible to get information about the status of an I/O |
| request. When the operation is performed truly asynchronously (as with |
| <code>aio_read</code> and <code>aio_write</code> and with <code>lio_listio</code> when the |
| mode is <code>LIO_NOWAIT</code>), one sometimes needs to know whether a |
| specific request already terminated and if so, what the result was. |
| The following two functions allow you to get this kind of information. |
| |
| <!-- aio.h --> |
| <!-- POSIX.1b --> |
| <div class="defun"> |
| — Function: int <b>aio_error</b> (<var>const struct aiocb *aiocbp</var>)<var><a name="index-aio_005ferror-1298"></a></var><br> |
| <blockquote><p>This function determines the error state of the request described by the |
| <code>struct aiocb</code> variable pointed to by <var>aiocbp</var>. If the |
| request has not yet terminated the value returned is always |
| <code>EINPROGRESS</code>. Once the request has terminated the value |
| <code>aio_error</code> returns is either 0 if the request completed |
| successfully or it returns the value which would be stored in the |
| <code>errno</code> variable if the request would have been done using |
| <code>read</code>, <code>write</code>, or <code>fsync</code>. |
| |
| <p>The function can return <code>ENOSYS</code> if it is not implemented. It |
| could also return <code>EINVAL</code> if the <var>aiocbp</var> parameter does not |
| refer to an asynchronous operation whose return status is not yet known. |
| |
| <p>When the sources are compiled with <code>_FILE_OFFSET_BITS == 64</code> this |
| function is in fact <code>aio_error64</code> since the LFS interface |
| transparently replaces the normal implementation. |
| </p></blockquote></div> |
| |
| <!-- aio.h --> |
| <!-- Unix98 --> |
| <div class="defun"> |
| — Function: int <b>aio_error64</b> (<var>const struct aiocb64 *aiocbp</var>)<var><a name="index-aio_005ferror64-1299"></a></var><br> |
| <blockquote><p>This function is similar to <code>aio_error</code> with the only difference |
| that the argument is a reference to a variable of type <code>struct |
| aiocb64</code>. |
| |
| <p>When the sources are compiled with <code>_FILE_OFFSET_BITS == 64</code> this |
| function is available under the name <code>aio_error</code> and so |
| transparently replaces the interface for small files on 32 bit |
| machines. |
| </p></blockquote></div> |
| |
| <!-- aio.h --> |
| <!-- POSIX.1b --> |
| <div class="defun"> |
| — Function: ssize_t <b>aio_return</b> (<var>const struct aiocb *aiocbp</var>)<var><a name="index-aio_005freturn-1300"></a></var><br> |
| <blockquote><p>This function can be used to retrieve the return status of the operation |
| carried out by the request described in the variable pointed to by |
| <var>aiocbp</var>. As long as the error status of this request as returned |
| by <code>aio_error</code> is <code>EINPROGRESS</code> the return of this function is |
| undefined. |
| |
| <p>Once the request is finished this function can be used exactly once to |
| retrieve the return value. Following calls might lead to undefined |
| behavior. The return value itself is the value which would have been |
| returned by the <code>read</code>, <code>write</code>, or <code>fsync</code> call. |
| |
| <p>The function can return <code>ENOSYS</code> if it is not implemented. It |
| could also return <code>EINVAL</code> if the <var>aiocbp</var> parameter does not |
| refer to an asynchronous operation whose return status is not yet known. |
| |
| <p>When the sources are compiled with <code>_FILE_OFFSET_BITS == 64</code> this |
| function is in fact <code>aio_return64</code> since the LFS interface |
| transparently replaces the normal implementation. |
| </p></blockquote></div> |
| |
| <!-- aio.h --> |
| <!-- Unix98 --> |
| <div class="defun"> |
| — Function: int <b>aio_return64</b> (<var>const struct aiocb64 *aiocbp</var>)<var><a name="index-aio_005freturn64-1301"></a></var><br> |
| <blockquote><p>This function is similar to <code>aio_return</code> with the only difference |
| that the argument is a reference to a variable of type <code>struct |
| aiocb64</code>. |
| |
| <p>When the sources are compiled with <code>_FILE_OFFSET_BITS == 64</code> this |
| function is available under the name <code>aio_return</code> and so |
| transparently replaces the interface for small files on 32 bit |
| machines. |
| </p></blockquote></div> |
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