flags.c revision 330897 
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)
36static char sccsid[] = "@(#)flags.c	8.1 (Berkeley) 6/4/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/flags.c 330897 2018-03-14 03:19:51Z eadler $");
40
41#include <sys/types.h>
42#include <sys/file.h>
43#include <stdio.h>
44#include <errno.h>
45
46#include "local.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 0 on error.
52 */
53int
54__sflags(const char *mode, int *optr)
55{
56	int ret, m, o, known;
57
58	switch (*mode++) {
59
60	case 'r':	/* open for reading */
61		ret = __SRD;
62		m = O_RDONLY;
63		o = 0;
64		break;
65
66	case 'w':	/* open for writing */
67		ret = __SWR;
68		m = O_WRONLY;
69		o = O_CREAT | O_TRUNC;
70		break;
71
72	case 'a':	/* open for appending */
73		ret = __SWR;
74		m = O_WRONLY;
75		o = O_CREAT | O_APPEND;
76		break;
77
78	default:	/* illegal mode */
79		errno = EINVAL;
80		return (0);
81	}
82
83	do {
84		known = 1;
85		switch (*mode++) {
86		case 'b':
87			/* 'b' (binary) is ignored */
88			break;
89		case '+':
90			/* [rwa][b]\+ means read and write */
91			ret = __SRW;
92			m = O_RDWR;
93			break;
94		case 'x':
95			/* 'x' means exclusive (fail if the file exists) */
96			o |= O_EXCL;
97			break;
98		case 'e':
99			/* set close-on-exec */
100			o |= O_CLOEXEC;
101			break;
102		case 'v':
103			/* verify */
104			o |= O_VERIFY;
105			break;
106		default:
107			known = 0;
108			break;
109		}
110	} while (known);
111
112	if ((o & O_EXCL) != 0 && m == O_RDONLY) {
113		errno = EINVAL;
114		return (0);
115	}
116
117	*optr = m | o;
118	return (ret);
119}
120