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
flagsargument 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_MOVEcan successfully move the pages; if this flag is not specified, then a subsequent splice(2)SPLICE_F_MOVEmust 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)
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