vmsplice — splice user pages into a pipe
#define _GNU_SOURCE #include <fcntl.h> #include <sys/uio.h>
long
vmsplice( |
int | fd, |
| const struct iovec * | iov, | |
| unsigned long | nr_segs, | |
| unsigned int | flags); |
The vmsplice() system call
maps nr_segs ranges
of user memory described by iov into a pipe. The file
descriptor fd must
refer to a pipe.
The pointer iov
points to an array of iovec
structures as defined in <sys/uio.h>
struct iovec { void * iov_base;size_t iov_len;};
The flags argument
is a bit mask that is composed by ORing together zero or more
of the following values:
SPLICE_F_MOVEUnused for vmsplice();
see splice(2).
SPLICE_F_NONBLOCKDo not block on I/O; see splice(2) for further details.
SPLICE_F_MORECurrently has no effect for vmsplice(), but may be implemented in
the future; see splice(2).
SPLICE_F_GIFTThe user pages are a gift to the kernel. The
application may not modify this memory ever, or page
cache and on-disk data may differ. Gifting pages to the
kernel means that a subsequent splice(2)
SPLICE_F_MOVE can
successfully move the pages; if this flag is not
specified, then a subsequent splice(2)
SPLICE_F_MOVE must copy
the pages. Data must also be properly page aligned,
both in memory and length.
Upon successful completion, vmsplice() returns the number of bytes
transferred to the pipe. On error, vmsplice() returns −1 and
errno is set to indicate the
error.
fd either
not valid, or doesn't refer to a pipe.
nr_segs is 0
or greater than IOV_MAX;
or memory not aligned if SPLICE_F_GIFT set.
Out of memory.
vmsplice() follows the other
vectorized read/write type functions when it comes to
limitations on number of segments being passed in. This limit
is IOV_MAX as defined in
<limits.h>
At the time of this writing, that limit is 1024.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
This manpage is Copyright (C) 2006 Jens Axboe and Copyright (C) 2006 Michael Kerrisk <mtk.manpagesgmail.com> Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |