cosmopolitan/libc/calls/clock_gettime.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=8 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/assert.h"
#include "libc/calls/internal.h"
#include "libc/calls/struct/timeval.h"
#include "libc/fmt/conv.h"
#include "libc/nt/synchronization.h"
#include "libc/sysv/errfuns.h"

/**
 * Returns nanosecond time.
 *
 * This is a high-precision timer that supports multiple definitions of
 * time. Among the more popular is CLOCK_MONOTONIC. This function has a
 * zero syscall implementation of that on modern x86.
 *
 * @param clockid can be CLOCK_REALTIME, CLOCK_MONOTONIC, etc. noting
 *     that on Linux CLOCK_MONOTONIC is redefined to use the monotonic
 *     clock that's actually monotonic lool
 * @param ts is where the result is stored
 * @return 0 on success, or -1 w/ errno
 * @error ENOSYS if clockid isn't available; in which case this function
 *     guarantees an ordinary timestamp is still stored to ts; and
 *     errno isn't restored to its original value, to detect prec. loss
 * @see strftime(), gettimeofday()
 * @asyncsignalsafe
 */
int clock_gettime(int clockid, struct timespec *ts) {
  int rc;
  axdx_t ad;
  struct NtFileTime ft;
  if (!ts) return efault();
  if (!IsWindows()) {
    if ((rc = sys_clock_gettime(clockid, ts)) == -1 && errno == ENOSYS) {
      ad = sys_gettimeofday((struct timeval *)ts, NULL, NULL);
      assert(ad.ax != -1);
      if (SupportsXnu() && ad.ax) {
        ts->tv_sec = ad.ax;
        ts->tv_nsec = ad.dx;
      }
      ts->tv_nsec *= 1000;
      rc = 0;
    }
    return rc;
  } else {
    GetSystemTimeAsFileTime(&ft);
    *ts = FileTimeToTimeSpec(ft);
    return 0;
  }
}