/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/struct/iovec.h"
#include "libc/calls/struct/iovec.internal.h"
#include "libc/errno.h"

/**
 * Transfers memory to pipe.
 *
 * @param flags can have SPLICE_F_{MOVE,NONBLOCK,MORE,GIFT}
 * @return number of bytes actually transferred, or -1 w/ errno
 */
ssize_t vmsplice(int fd, const struct iovec *chunks, int64_t count,
                 uint32_t flags) {
  int olderr;
  ssize_t wrote;
  olderr = errno;
  if ((wrote = sys_vmsplice(fd, chunks, count, flags)) == -1) {
    errno = olderr;
    if (count) {
      wrote = write(fd, chunks[0].iov_base, chunks[0].iov_len);
    } else {
      wrote = write(fd, NULL, 0);
    }
  }
  return wrote;
}