AIO_READ(3) | Library Functions Manual | AIO_READ(3) |
aio_read
—
#include <aio.h>
int
aio_read
(struct
aiocb *aiocbp);
aio_read
() system call allows the calling process to
read aiocbp->aio_nbytes from the descriptor
aiocbp->aio_fildes beginning at the offset
aiocbp->aio_offset into the buffer pointed to by
aiocbp->aio_buf. The call returns immediately after
the read request has been enqueued to the descriptor; the read may or may not
have completed at the time the call returns.
If _POSIX_PRIORITIZED_IO
is defined, and
the descriptor supports it, then the enqueued operation is submitted at a
priority equal to that of the calling process minus
aiocbp->aio_reqprio.
The aiocbp->aio_lio_opcode argument is
ignored by the aio_read
() system call.
The aiocbp pointer may be subsequently used
as an argument to aio_return
() and
aio_error
() in order to determine return or error
status for the enqueued operation while it is in progress.
If the request could not be enqueued (generally due to invalid arguments), then the call returns without having enqueued the request.
If the request is successfully enqueued, the value of aiocbp->aio_offset can be modified during the request as context, so this value must not be referenced after the request is enqueued.
The asynchronous I/O control buffer aiocbp
should be zeroed before the aio_read
() call to avoid
passing bogus context information to the kernel.
Modifications of the Asynchronous I/O Control Block structure or the buffer contents after the request has been enqueued, but before the request has completed, are not allowed.
If the file offset in aiocbp->aio_offset is past the offset maximum for aiocbp->aio_fildes, no I/O will occur.
aio_read
() function returns the value 0 if
successful; otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
aio_read
() system call will fail if:
EAGAIN
]The following conditions may be synchronously detected when the
aio_read
() system call is made, or asynchronously,
at any time thereafter. If they are detected at call time,
aio_read
() returns -1 and sets
errno appropriately; otherwise the
aio_return
() system call must be called, and will
return -1, and aio_error
() must be called to
determine the actual value that would have been returned in
errno.
EBADF
]EINVAL
]EOVERFLOW
]If the request is successfully enqueued, but subsequently
cancelled or an error occurs, the value returned by the
aio_return
() system call is per the
read(2) system call, and the
value returned by the aio_error
() system call is
either one of the error returns from the
read(2) system call, or one
of:
aio_read
() system call is expected to conform to the
IEEE Std 1003.1-2001 (“POSIX.1”)
standard.
aio_read
() system call first appeared in
NetBSD 5.0.
May 17, 2010 | NetBSD 9.0 |