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
;/* Starting address */ size_t iov_len
;/* Number of bytes */ }; The
flags
argument is a bit mask that is composed by ORing together zero or more of the following values:
SPLICE_F_MOVE
Unused for
vmsplice
(); see splice(2).SPLICE_F_NONBLOCK
Do not block on I/O; see splice(2) for further details.
SPLICE_F_MORE
Currently has no effect for
vmsplice
(), but may be implemented in the future; see splice(2).SPLICE_F_GIFT
The 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.
splice(2), tee(2), feature_test_macros(7)
|