/*-*- 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                              │
│                                                                              │
│ This program is free software; you can redistribute it and/or modify         │
│ it under the terms of the GNU General Public License as published by         │
│ the Free Software Foundation; version 2 of the License.                      │
│                                                                              │
│ This program is distributed in the hope that it will be useful, but          │
│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
│ General Public License for more details.                                     │
│                                                                              │
│ You should have received a copy of the GNU General Public License            │
│ along with this program; if not, write to the Free Software                  │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
│ 02110-1301 USA                                                               │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/dce.h"

/**
 * Drops hints to O/S about intended I/O behavior.
 *
 * It makes a huge difference. For example, when copying a large file,
 * it can stop the system from persisting GBs of useless memory content.
 *
 * @param len 0 means ‘til end of file
 * @param advice can be MADV_SEQUENTIAL, MADV_RANDOM, etc.
 * @return -1 on error
 * @syscall
 */
int fadvise(int fd, uint64_t offset, uint64_t len, int advice) {
  if (!IsWindows()) {
    return fadvise$sysv(fd, offset, len, advice); /* linux & freebsd */
  } else {
    return fadvise$nt(fd, offset, len, advice);
  }
}