NAME
aaiioorreeaadd - asynchronous read from a file (REALTIME)
LLIIBBRRAARRYY
Standard C Library (libc, -lc)
SYNOPSIS
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int
aaiioorreeaadd(struct aiocb *aiocbp);
DESCRIPTION
The aaiioorreeaadd() system call allows the calling process to read
aiocbp->aionbytes from the descriptor aiocbp->aiofildes, beginning at
the offset aiocbp->aiooffset, into the buffer pointed to by
aiocbp->aiobuf. 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 POSIXPRIORITIZEDIO 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->aioreqprio.
The aiocbp->aiolioopcode argument is ignored by the aaiioorreeaadd() system
call.
The aiocbp pointer may be subsequently used as an argument to
aaiioorreettuurrnn() and aaiiooeerrrroorr() 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 argu-
ments), then the call returns without having enqueued the request.
If the request is successfully enqueued, the value of aiocbp->aiooffset
can be modified during the request as context, so this value must not be
referenced after the request is enqueued.
RREESSTTRRIICCTTIIOONNSS
The Asynchronous I/O Control Block structure pointed to by aiocbp and the
buffer that the aiocbp->aiobuf member of that structure references must
remain valid until the operation has completed. For this reason, use of
auto (stack) variables for these objects is discouraged.
The asynchronous I/O control buffer aiocbp should be zeroed before the
aaiioorreeaadd() 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->aiooffset is past the offset maximum for
aiocbp->aiofildes, no I/O will occur.
RETURN VALUES
The aaiioorreeaadd() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
DIAGNOSTICS None.
EERRRROORRSS
The aaiioorreeaadd() system call will fail if:
[EAGAIN] Because of system resource limitations, the request
was not queued.
[ENOSYS] The aaiioorreeaadd() system call is not supported.
The following conditions may be synchronously detected when the
aaiioorreeaadd() system call is made, or asynchronously, at any time there-
after. If they are detected at call time, aaiioorreeaadd() returns -1 and sets
errno appropriately. Otherwise, the aaiioorreettuurrnn() system call must be
called. It will return -1; aaiiooeerrrroorr() must then be called to determine
the actual value that would have been returned in errno.
[EBADF] The aiocbp->aiofildes argument is invalid.
[EINVAL] The offset aiocbp->aiooffset is not valid, the prior-
ity specified by aiocbp->aioreqprio is not a valid
priority, or the number of bytes specified by
aiocbp->aionbytes is not valid.
[EOVERFLOW] The file is a regular file, aiocbp->aionbytes is
greater than zero, the starting offset in
aiocbp->aiooffset is before the end of the file, but
is at or beyond the aiocbp->aiofildes offset maximum.
If the request is successfully enqueued, but subsequently cancelled or an
error occurs, the value returned by the aaiioorreettuurrnn() system call is per
the read(2) system call, and the value returned by the aaiiooeerrrroorr() system
call is either one of the error returns from the read(2) system call, or
one of:
[EBADF] The aiocbp->aiofildes argument is invalid for read-
ing.
[ECANCELED] The request was explicitly cancelled via a call to
aaiiooccaanncceell().
[EINVAL] The offset aiocbp->aiooffset would be invalid.
SEE ALSO
aiocancel(2), aioerror(2), aioreturn(2), aiosuspend(2), aiowrite(2),
aio(4)
STANDARDS The aaiioorreeaadd() system call is expected to conform to the IEEE Std 1003.1
(``POSIX.1'') standard.
HISTORY The aaiioorreeaadd() system call first appeared in FreeBSD 3.0.
AUTHORS This manual page was written by Terry Lambert .
BUGS
Invalid information in aiocbp->aiocbprivate may confuse the kernel.
BSD November 17, 1998 BSD