wcsftime.c revision 103218 
1/*-
2 * Copyright (c) 2002 Tim J. Robbins
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/lib/libc/locale/wcsftime.c 103218 2002-09-11 08:57:11Z tjr $");
29
30#include <limits.h>
31#include <stdlib.h>
32#include <time.h>
33#include <wchar.h>
34
35/*
36 * Convert date and time to a wide-character string.
37 *
38 * This is the wide-character counterpart of strftime(). So that we do not
39 * have to duplicate the code of strftime(), we convert the format string to
40 * multibyte, call strftime(), then convert the result back into wide
41 * characters.
42 *
43 * This technique loses in the presence of stateful multibyte encoding if any
44 * of the conversions in the format string change conversion state. When
45 * stateful encoding is implemented, we will need to reset the state between
46 * format specifications in the format string.
47 */
48size_t
49wcsftime(wchar_t * __restrict wcs, size_t maxsize,
50    const wchar_t * __restrict format, const struct tm * __restrict timeptr)
51{
52	static const mbstate_t initial;
53	mbstate_t state;
54	char *dst, *sformat;
55	size_t n, sflen;
56
57	/*
58	 * Convert the supplied format string to a multibyte representation
59	 * for strftime(), which only handles single-byte characters.
60	 */
61	state = initial;
62	sflen = wcsrtombs(NULL, &format, 0, &state);
63	if (sflen == (size_t)-1)
64		return (0);
65	sformat = alloca(sflen + 1);
66	state = initial;
67	wcsrtombs(sformat, &format, sflen + 1, &state);
68
69	/*
70	 * Allocate memory for longest multibyte sequence that will fit
71	 * into the caller's buffer and call strftime() to fill it.
72	 * Then, copy and convert the result back into wide characters in
73	 * the caller's buffer.
74	 */
75	if (SIZE_T_MAX / MB_CUR_MAX <= maxsize)
76		/* maxsize is prepostorously large - avoid int. overflow. */
77		return (0);
78	dst = alloca(maxsize * MB_CUR_MAX);
79	if (strftime(dst, maxsize, sformat, timeptr) == 0)
80		return (0);
81	state = initial;
82	n = mbsrtowcs(wcs, (const char **)&dst, maxsize, &state);
83	if (n == (size_t)-2 || n == (size_t)-1 || dst != NULL)
84		return (0);
85
86	return (n);
87}
88