/*-*- 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/sock/select.h"
#include "libc/calls/cp.internal.h"
#include "libc/calls/struct/itimerval.internal.h"
#include "libc/calls/struct/timespec.h"
#include "libc/calls/struct/timeval.h"
#include "libc/calls/struct/timeval.internal.h"
#include "libc/dce.h"
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/describeflags.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/sock/internal.h"
#include "libc/sysv/errfuns.h"

/**
 * Does what poll() does except with bitset API.
 *
 * This system call is supported on all platforms. However, on Windows,
 * this is polyfilled to translate into poll(). So it's recommended that
 * poll() be used instead.
 *
 * @raise ECANCELED if thread was cancelled in masked mode
 * @raise EINTR if signal was delivered
 * @cancellationpoint
 * @asyncsignalsafe
 * @threadsafe
 * @norestart
 */
int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
           struct timeval *timeout) {
  int rc;
  struct timeval tv, *tvp;
  POLLTRACE("select(%d, %p, %p, %p, %s) → ...", nfds, readfds, writefds,
            exceptfds, DescribeTimeval(0, timeout));

  // the linux kernel modifies timeout
  if (timeout) {
    if (IsAsan() && !__asan_is_valid(timeout, sizeof(*timeout))) {
      return efault();
    }
    tv = *timeout;
    tvp = &tv;
  } else {
    tvp = 0;
  }

  BEGIN_CANCELLATION_POINT;
  if (nfds < 0) {
    rc = einval();
  } else if (IsAsan() &&
             ((readfds && !__asan_is_valid(readfds, FD_SIZE(nfds))) ||
              (writefds && !__asan_is_valid(writefds, FD_SIZE(nfds))) ||
              (exceptfds && !__asan_is_valid(exceptfds, FD_SIZE(nfds))))) {
    rc = efault();
  } else if (!IsWindows()) {
#ifdef __aarch64__
    struct timespec ts, *tsp;
    if (timeout) {
      ts.tv_sec = timeout->tv_sec;
      ts.tv_nsec = timeout->tv_usec * 1000;
      tsp = &ts;
    } else {
      tsp = 0;
    }
    rc = sys_pselect(nfds, readfds, writefds, exceptfds, tsp, 0);
#else
    rc = sys_select(nfds, readfds, writefds, exceptfds, tvp);
#endif
  } else {
    rc = sys_select_nt(nfds, readfds, writefds, exceptfds, tvp, 0);
  }
  END_CANCELLATION_POINT;

  POLLTRACE("select(%d, %p, %p, %p, [%s]) → %d% m", nfds, readfds, writefds,
            exceptfds, DescribeTimeval(rc, tvp), rc);
  return rc;
}