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Diffstat (limited to 'lib/libc/sys/aio_read.2')
| -rw-r--r-- | lib/libc/sys/aio_read.2 | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/lib/libc/sys/aio_read.2 b/lib/libc/sys/aio_read.2 new file mode 100644 index 000000000000..ddf4f7630239 --- /dev/null +++ b/lib/libc/sys/aio_read.2 @@ -0,0 +1,214 @@ +.\" Copyright (c) 1998 Terry Lambert +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd November 17, 1998 +.Dt AIO_READ 2 +.Os +.Sh NAME +.Nm aio_read +.Nd asynchronous read from a file (REALTIME) +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In aio.h +.Ft int +.Fn aio_read "struct aiocb *iocb" +.Sh DESCRIPTION +The +.Fn aio_read +system call allows the calling process to read +.Fa iocb->aio_nbytes +from the descriptor +.Fa iocb->aio_fildes +beginning at the offset +.Fa iocb->aio_offset +into the buffer pointed to by +.Fa iocb->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. +.Pp +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 +.Fa iocb->aio_reqprio . +.Pp +The +.Fa iocb->aio_lio_opcode +argument +is ignored by the +.Fn aio_read +system call. +.Pp +The +.Fa iocb +pointer may be subsequently used as an argument to +.Fn aio_return +and +.Fn aio_error +in order to determine return or error status for the enqueued operation +while it is in progress. +.Pp +If the request could not be enqueued (generally due to invalid arguments), +then the call returns without having enqueued the request. +.Pp +If the request is successfully enqueued, the value of +.Fa iocb->aio_offset +can be modified during the request as context, so this value must +not be referenced after the request is enqueued. +.Sh RESTRICTIONS +The Asynchronous I/O Control Block structure pointed to by +.Fa iocb +and the buffer that the +.Fa iocb->aio_buf +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. +.Pp +The asynchronous I/O control buffer +.Fa iocb +should be zeroed before the +.Fn aio_read +call to avoid passing bogus context information to the kernel. +.Pp +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. +.Pp +If the file offset in +.Fa iocb->aio_offset +is past the offset maximum for +.Fa iocb->aio_fildes , +no I/O will occur. +.Sh RETURN VALUES +.Rv -std aio_read +.Sh DIAGNOSTICS +None. +.Sh ERRORS +The +.Fn aio_read +system call will fail if: +.Bl -tag -width Er +.It Bq Er EAGAIN +The request was not queued because of system resource limitations. +.It Bq Er ENOSYS +The +.Fn aio_read +system call is not supported. +.El +.Pp +The following conditions may be synchronously detected when the +.Fn aio_read +system call is made, or asynchronously, at any time thereafter. +If they +are detected at call time, +.Fn aio_read +returns -1 and sets +.Va errno +appropriately; otherwise the +.Fn aio_return +system call must be called, and will return -1, and +.Fn aio_error +must be called to determine the actual value that would have been +returned in +.Va errno . +.Bl -tag -width Er +.It Bq Er EBADF +The +.Fa iocb->aio_fildes +argument +is invalid. +.It Bq Er EINVAL +The offset +.Fa iocb->aio_offset +is not valid, the priority specified by +.Fa iocb->aio_reqprio +is not a valid priority, or the number of bytes specified by +.Fa iocb->aio_nbytes +is not valid. +.It Bq Er EOVERFLOW +The file is a regular file, +.Fa iocb->aio_nbytes +is greater than zero, the starting offset in +.Fa iocb->aio_offset +is before the end of the file, but is at or beyond the +.Fa iocb->aio_fildes +offset maximum. +.El +.Pp +If the request is successfully enqueued, but subsequently cancelled +or an error occurs, the value returned by the +.Fn aio_return +system call is per the +.Xr read 2 +system call, and the value returned by the +.Fn aio_error +system call is either one of the error returns from the +.Xr read 2 +system call, or one of: +.Bl -tag -width Er +.It Bq Er EBADF +The +.Fa iocb->aio_fildes +argument +is invalid for reading. +.It Bq Er ECANCELED +The request was explicitly cancelled via a call to +.Fn aio_cancel . +.It Bq Er EINVAL +The offset +.Fa iocb->aio_offset +would be invalid. +.El +.Sh SEE ALSO +.Xr aio_cancel 2 , +.Xr aio_error 2 , +.Xr aio_return 2 , +.Xr aio_suspend 2 , +.Xr aio_waitcomplete 2 , +.Xr aio_write 2 , +.Xr siginfo 3 , +.Xr aio 4 +.Sh STANDARDS +The +.Fn aio_read +system call is expected to conform to the +.St -p1003.1 +standard. +.Sh HISTORY +The +.Fn aio_read +system call first appeared in +.Fx 3.0 . +.Sh AUTHORS +This +manual page was written by +.An Terry Lambert Aq terry@whistle.com . +.Sh BUGS +Invalid information in +.Fa iocb->_aiocb_private +may confuse the kernel. |