text: /*-*- 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/bits/weaken.h"
  #include "libc/calls/calls.h"
  #include "libc/calls/internal.h"
  #include "libc/calls/struct/metastat.internal.h"
  #include "libc/dce.h"
  #include "libc/errno.h"
  #include "libc/intrin/asan.internal.h"
  #include "libc/sysv/consts/at.h"
  #include "libc/sysv/errfuns.h"
  #include "libc/zipos/zipos.internal.h"
  
  /**
   * Returns true if file exists and is a regular file.
   *
   * This function is equivalent to:
   *
   *     return fstatat(AT_FDCWD, path, &st, AT_SYMLINK_NOFOLLOW) != -1 &&
   *            S_ISREG(st.st_mode);
   *
   * Except faster and with fewer dependencies.
   *
   * @see isdirectory(), ischardev(), issymlink()
   */
  bool isregularfile(const char *path) {
    int rc, e;
    union metastat st;
    struct ZiposUri zipname;
    if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
    if (weaken(__zipos_open) && weaken(__zipos_parseuri)(path, &zipname) != -1) {
      e = errno;
      if (weaken(__zipos_stat)(&zipname, &st.cosmo) != -1) {
        return S_ISREG(st.cosmo.st_mode);
      } else {
        errno = e;
        return false;
      }
    } else if (IsMetal()) {
      return false;
    } else if (!IsWindows()) {
      e = errno;
      if (__sys_fstatat(AT_FDCWD, path, &st, AT_SYMLINK_NOFOLLOW) != -1) {
        return S_ISREG(METASTAT(st, st_mode));
      } else {
        errno = e;
        return false;
      }
    } else {
      return isregularfile_nt(path);
    }
  }
  