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

/**
 * Checks if effective user can access path in particular ways.
 *
 * @param dirfd is normally AT_FDCWD but if it's an open directory and
 *     file is a relative path, then file is opened relative to dirfd
 * @param path is a filename or directory
 * @param amode can be `R_OK`, `W_OK`, `X_OK`, or `F_OK`
 * @param flags can have `AT_EACCESS` and/or `AT_SYMLINK_NOFOLLOW`
 * @return 0 if ok, or -1 and sets errno
 * @raise EINVAL if `mode` has bad value
 * @raise EPERM if pledge() is in play without rpath promise
 * @raise EACCES if access for requested `mode` would be denied
 * @raise ENOTDIR if a directory component in `path` exists as non-directory
 * @raise ENOENT if component of `path` doesn't exist or `path` is empty
 * @raise ENOTSUP if `path` is a zip file and `dirfd` isn't `AT_FDCWD`
 * @note on Linux `flags` is only supported on Linux 5.8+
 * @asyncsignalsafe
 */
int faccessat(int dirfd, const char *path, int amode, int flags) {
  int e, rc;
  struct ZiposUri zipname;
  if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
    rc = efault();
  } else if (__isfdkind(dirfd, kFdZip)) {
    rc = enotsup();
  } else if (_weaken(__zipos_open) &&
             _weaken(__zipos_parseuri)(path, &zipname) != -1) {
    rc = _weaken(__zipos_access)(&zipname, amode);
  } else if (!IsWindows()) {
    e = errno;
    if (!flags) goto NoFlags;
    if ((rc = sys_faccessat2(dirfd, path, amode, flags)) == -1) {
      if (errno == ENOSYS) {
        errno = e;
      NoFlags:
        rc = sys_faccessat(dirfd, path, amode, flags);
      }
    }
  } else {
    rc = sys_faccessat_nt(dirfd, path, amode, flags);
  }
  STRACE("faccessat(%s, %#s, %#o, %#x) â %d% m", DescribeDirfd(dirfd), path,
         amode, flags, rc);
  return rc;
}
