vmsplice

       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <fcntl.h>
       #include <sys/uio.h>

       ssize_t vmsplice(int fd, const struct iovec *iov,
                        unsigned long nr_segs, unsigned int flags);

DESCRIPTION
       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 appli-
                          cation  may  not  modify this memory ever, otherwise
                          the 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 subse-
                          quent splice(2) SPLICE_F_MOVE must copy  the  pages.
                          Data  must  also  be  properly page aligned, both in
                          memory and length.

RETURN VALUE
       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.

ERRORS
       EAGAIN SPLICE_F_NONBLOCK was specified  in  flags,  and  the  operation
              would block.

       EBADF  fd either not valid, or doesn't refer to a pipe.

       EINVAL nr_segs  is  greater  than  IOV_MAX;  or  memory  not aligned if
              SPLICE_F_GIFT set.

       This  limit is IOV_MAX as defined in <limits.h>.  Currently, this limit
       is 1024.

SEE ALSO
       splice(2), tee(2)

COLOPHON
       This page is part of release 4.04 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       http://www.kernel.org/doc/man-pages/.

Linux                             2014-10-02                       VMSPLICE(2)
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