cosmopolitan/libc/calls/umask.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 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.      │
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│ 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/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/strace.h"
#include "libc/sysv/consts/nr.h"

/**
 * Sets file mode creation mask.
 *
 * On Windows, the value of umask() determines how Cosmopolitan goes
 * about creating synthetic `st_mode` bits. The default umask is 077
 * which is based on the assumption that Windows is being used for a
 * single user. Don't assume that Cosmopolitan Libc will help you to
 * secure a multitenant Windows computer.
 *
 * @return previous mask
 * @note always succeeds
 */
unsigned umask(unsigned newmask) {
  int oldmask;
  if (!IsWindows()) {
    oldmask = sys_umask(newmask);
  } else {
    oldmask = atomic_exchange(&__umask, newmask);
  }
  STRACE("umask(%#o) → %#o", oldmask);
  return oldmask;
}