NAME

       io_uring_prep_splice - prepare an splice request

SYNOPSIS

       #include <fcntl.h>
       #include <liburing.h>

       void io_uring_prep_splice(struct io_uring_sqe *sqe,
                                 int fd_in,
                                 int64_t off_in,
                                 int fd_out,
                                 int64_t off_out,
                                 unsigned int nbytes,
                                 unsigned int splice_flags);

DESCRIPTION

       The io_uring_prep_splice(3) function prepares a splice request. The submission queue entry
       sqe is setup to use as input the file descriptor fd_in at offset off_in, splicing data  to
       the  file  descriptor  at  fd_out  and  at offset off_out.  nbytes bytes of data should be
       spliced between the two descriptors.  splice_flags are modifier flags for  the  operation.
       See splice(2) for the generic splice flags.

       If the fd_out descriptor, IOSQE_FIXED_FILE can be set in the SQE to indicate that. For the
       input file, the io_uring specific SPLICE_F_FD_IN_FIXED can  be  set  in  splice_flags  and
       fd_in given as a registered file descriptor offset.

       If fd_in refers to a pipe, off_in is ignored and must be set to -1.

       If  fd_in  does  not  refer  to  a  pipe and off_in is -1, then nbytes are read from fd_in
       starting from the file offset, which is incremented by the number of bytes read.

       If fd_in does not refer to a pipe and off_in is not -1, then the starting offset of  fd_in
       will be off_in.

       The same rules apply to fd_out and off_out.

       This function prepares an async splice(2) request. See that man page for details.

RETURN VALUE

       None

ERRORS

       The  CQE  res field will contain the result of the operation. See the related man page for
       details on possible values. Note that where synchronous system calls  will  return  -1  on
       failure  and  set  errno to the actual error value, io_uring never uses errno.  Instead it
       returns the negated errno directly in the CQE res field.

SEE ALSO

       io_uring_get_sqe(3), io_uring_submit(3), io_uring_register(2), splice(2)

NOTES

       Note that even if fd_in or fd_out refers to a pipe, the splice operation  can  still  fail
       with  EINVAL  if  one  of the fd doesn't explicitly support splice operation, e.g. reading
       from terminal is unsupported from kernel 5.7 to 5.11.