plucky (3) io_uring_prep_splice.3.gz

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.