1  /*-
  2   * SPDX-License-Identifier: BSD-3-Clause
  3   *
  4   * Copyright (c) 1990, 1993
  5   *	The Regents of the University of California.  All rights reserved.
  6   *
  7   * This code is derived from software contributed to Berkeley by
  8   * Chris Torek.
  9   *
 10   * Redistribution and use in source and binary forms, with or without
 11   * modification, are permitted provided that the following conditions
 12   * are met:
 13   * 1. Redistributions of source code must retain the above copyright
 14   *    notice, this list of conditions and the following disclaimer.
 15   * 2. Redistributions in binary form must reproduce the above copyright
 16   *    notice, this list of conditions and the following disclaimer in the
 17   *    documentation and/or other materials provided with the distribution.
 18   * 3. Neither the name of the University nor the names of its contributors
 19   *    may be used to endorse or promote products derived from this software
 20   *    without specific prior written permission.
 21   *
 22   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 23   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 24   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 25   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 26   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 27   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 28   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 29   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 30   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 31   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 32   * SUCH DAMAGE.
 33   */
 34  
 35  #if defined(LIBC_SCCS) && !defined(lint)
 36  static char sccsid[] = "@(#)flags.c	8.1 (Berkeley) 6/4/93";
 37  #endif /* LIBC_SCCS and not lint */
 38  #include "bsd_compat.h"
 39  __FBSDID("$FreeBSD: head/lib/libc/stdio/flags.c 326025 2017-11-20 19:49:47Z pfg $");
 40  
 41  #include <sys/types.h>
 42  #include <sys/file.h>
 43  #include <stdio.h>
 44  #include <errno.h>
 45  #include <fcntl.h>
 46  #include "private/utils.h"
 47  
 48  /*
 49   * Return the (stdio) flags for a given mode.  Store the flags
 50   * to be passed to an _open() syscall through *optr.
 51   * Return 1 on error.
 52   */
 53  int
 54  checkflags(const char *mode, int *optr)
 55  {
 56  	int ret, m, o, known;
 57  	ret = 0;
 58  
 59  	switch (*mode++) {
 60  
 61  	case 'r':	/* open for reading */
 62  		ret = 1;
 63  		m = O_RDONLY;
 64  		o = 0;
 65  		break;
 66  
 67  	case 'w':	/* open for writing */
 68  		ret = 1;
 69  		m = O_WRONLY;
 70  		o = O_CREAT | O_TRUNC;
 71  		break;
 72  
 73  	case 'a':	/* open for appending */
 74  		ret = 1;
 75  		m = O_WRONLY;
 76  		o = O_CREAT | O_APPEND;
 77  		break;
 78  
 79  	default:	/* illegal mode */
 80  		errno = EINVAL;
 81  		return (0);
 82  	}
 83  
 84  	do {
 85  		known = 1;
 86  		switch (*mode++) {
 87  		case 'b':
 88  			/* 'b' (binary) is ignored */
 89  			break;
 90  		case '+':
 91  			/* [rwa][b]\+ means read and write */
 92  			ret = 1;
 93  			m = O_RDWR;
 94  			break;
 95  		case 'x':
 96  			/* 'x' means exclusive (fail if the file exists) */
 97  			o |= O_EXCL;
 98  			break;
 99  		case 'e':
100  			/* set close-on-exec */
101  			o |= O_CLOEXEC;
102  			break;
103  		default:
104  			known = 0;
105  			break;
106  		}
107  	} while (known);
108  
109  	if ((o & O_EXCL) != 0 && m == O_RDONLY) {
110  		errno = EINVAL;
111  		return (1);
112  	}
113  
114  	*optr = m | o;
115  	return (ret);
116  }