AIO_READ(3) AIO_READ(3)
aio_read, aio_read64 - asynchronous I/O read
#include <aio.h>
int aio_read(aiocb_t *aiocbp);
int aio_read64(aiocb64_t *aiocbp);
The aio_read() function allows the calling process to read aiocbp-
>aio_nbytes from the file associated with aiocbp->aio_fildes into the
buffer pointed to by aiocbp->aio_buf (see read(2)). The function call
returns when the read request has been initiated or, at a minimum, queued
for the file or device.
The aiocb->aio_sigevent defines how the calling process will be notified
upon I/O completion.
If sigev_notify is SIGEV_NONE, then no notification will be posted to the
calling application.
If sigev_notify is SIGEV_SIGNAL, then the signal specified in sigev_signo
will be sent to the calling process. If SA_SIGINFO is set for the signal
(see sigaction(2)) and the signal is in the range of SIGRTMIN and
SIGRTMAX then the signal will be queued to the process and the value in
sigev_value will be the si_value in the generated signal.
If sigev_notify is SIGEV_CALLBACK then the function sigev_func will be
called with sigev_value as the argument. Only one callback will be called
at a time, however programs should be careful to note that a callback may
be run in parallel with the calling process.
If sigev_notify is SIGEV_THREAD then the function sigev_notify_function
will be called by a new thread (see pthreads(5)) with sigev_value as the
argument. This thread is created when the event arrives with the
attributes specified in sigev_notify_attributes except that it is
automatically detached. The calling process should ensure there are
sufficient resources to create the thread.
All aio_read() calls must supply a complete aiocb->aio_sigevent
structure.
The aiocbp->aio_lio_opcode field is ignored by aio_read().
Prioritized I/O is not currently supported among asynchronous file
operations. aiocbp->aio_reqprio must be set to 0, otherwise the call
will fail.
Page 1
AIO_READ(3) AIO_READ(3)
After a call to aio_read the aiocbp may be used as an argument to
aio_error() and aio_return() in order to determine the error status and
return status, respectively, of the asynchronous operation while it is
proceeding. If an error condition is encountered during queueing, the
function call returns without having initiated or queued the request.
After a successful call to enqueue an asynchronous I/O operation, the
value of the file offset for the file is undefined.
If the buffer pointed to by aiocbp->aio_buf or the control block pointed
to by aiocbp changes or becomes an illegal address prior to asynchronous
I/O completion then the behavior is undefined. Simultaneous asynchronous
operations using the same aiocbp produce undefined results.
For any system action that changes the process memory space while an
asynchronous I/O is outstanding to the address range being changed, the
result of that asynchronous I/O is undefined.
The aio_read64() function is identical to aio_read() except that it takes
an aiocb64_t * (see <aio.h>). This structure allows for the
specification of a file offset greater than 2 Gigabytes.
aio_write(3), lio_listio(3), aio_error(3), aio_return(3), aio_hold(3),
aio_cancel(3), aio_sgi_init(3), aio_fsync(3), read(2), lseek(2),
close(2), _exit(2), exec(2), fork(2), pthreads(5), sysconf(3C).
The aio_read() returns the value 0 to the calling process if the I/O
operation is successfully queued; otherwise, the function shall return
the value -1 and shall set errno to indicate the error.
[EAGAIN] The requested asynchronous I/O operation was not queued
due to system resource limitations. Often this is due to
exceeding the maximum number of asynchronous I/O
operations for the system. The maximum can be checked with
a call to sysconf() with an argument of _SC_AIO_MAX.
Each of the following conditions may be detected synchronously at the
time of the call to aio_read() , or asynchronously. If any of the
conditions below are detected synchronously at the time of the call, the
aio_read() function shall return -1 and set errno to the corresponding
value. If any of the conditions below are detected asynchronously, the
return status of the asynchronous operation shall be set to -1 and the
error status of the asynchronous operation shall be set to the
corresponding value.
[EBADF] The aiocbp->aio_fildes argument is not a valid file
descriptor open for reading.
Page 2
AIO_READ(3) AIO_READ(3)
[EINVAL] The file offset value implied by aiocbp->aio_offset would
be invalid, aiocbp->aio_reqprio is not a valid value, or
aiocbp->aio_nbytes is an invalid value.
In the case that the aio_read() successfully queues the I/O operation,
the return status of the asynchronous operation shall be one of the
values normally returned by the read(2) function call. If the operation
is successfully queued, but is subsequently canceled or encounters an
error, the error status for the asynchronous operation shall contain one
of the values normally set by the read(2) function call, or one of the
following:
[EBADF] The aiocbp->aio_fildes argument is not a valid file
descriptor open for reading.
[EINVAL] The file offset value implied by aiocbp->aio_offset would
be invalid.
[ECANCELED] The requested I/O was canceled before the I/O completed
due to an explicit aio_cancel(3) request.
PPPPaaaaggggeeee 3333 [ Back ]
|
