以下是strptime的开源实现。如果许可证符合您的合法身份，您可以使用它。
无耻地从here盗取。
/* $NetBSD: strptime.c,v 1.28 2008/04/28 20:23:01 martin Exp $ */
/*-
* Copyright (c) 1997, 1998, 2005, 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code was contributed to The NetBSD Foundation by Klaus Klein.
* Heavily optimised by David Laight
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: strptime.c,v 1.28 2008/04/28 20:23:01 martin Exp $");
#endif
#include "namespace.h"
#include <sys/localedef.h>
#include <ctype.h>
#include <locale.h>
#include <string.h>
#include <time.h>
#include <tzfile.h>
#ifdef __weak_alias
__weak_alias(strptime,_strptime)
#endif
#define _ctloc(x) (_CurrentTimeLocale->x)
/*
* We do not implement alternate representations. However, we always
* check whether a given modifier is allowed for a certain conversion.
*/
#define ALT_E 0x01
#define ALT_O 0x02
#define LEGAL_ALT(x) { if (alt_format & ~(x)) return NULL; }
static const char gmt[4] = { "GMT" };
static const u_char *conv_num(const unsigned char *, int *, uint, uint);
static const u_char *find_string(const u_char *, int *, const char * const *,
const char * const *, int);
char *
strptime(const char *buf, const char *fmt, struct tm *tm)
{
unsigned char c;
const unsigned char *bp;
int alt_format, i, split_year = 0;
const char *new_fmt;
bp = (const u_char *)buf;
while (bp != NULL && (c = *fmt++) != '\0') {
/* Clear `alternate' modifier prior to new conversion. */
alt_format = 0;
i = 0;
/* Eat up white-space. */
if (isspace(c)) {
while (isspace(*bp))
bp++;
continue;
}
if (c != '%')
goto literal;
again: switch (c = *fmt++) {
case '%': /* "%%" is converted to "%". */
literal:
if (c != *bp++)
return NULL;
LEGAL_ALT(0);
continue;
/*
* "Alternative" modifiers. Just set the appropriate flag
* and start over again.
*/
case 'E': /* "%E?" alternative conversion modifier. */
LEGAL_ALT(0);
alt_format |= ALT_E;
goto again;
case 'O': /* "%O?" alternative conversion modifier. */
LEGAL_ALT(0);
alt_format |= ALT_O;
goto again;
/*
* "Complex" conversion rules, implemented through recursion.
*/
case 'c': /* Date and time, using the locale's format. */
new_fmt = _ctloc(d_t_fmt);
goto recurse;
case 'D': /* The date as "%m/%d/%y". */
new_fmt = "%m/%d/%y";
LEGAL_ALT(0);
goto recurse;
case 'F': /* The date as "%Y-%m-%d". */
new_fmt = "%Y-%m-%d";
LEGAL_ALT(0);
goto recurse;
case 'R': /* The time as "%H:%M". */
new_fmt = "%H:%M";
LEGAL_ALT(0);
goto recurse;
case 'r': /* The time in 12-hour clock representation. */
new_fmt =_ctloc(t_fmt_ampm);
LEGAL_ALT(0);
goto recurse;
case 'T': /* The time as "%H:%M:%S". */
new_fmt = "%H:%M:%S";
LEGAL_ALT(0);
goto recurse;
case 'X': /* The time, using the locale's format. */
new_fmt =_ctloc(t_fmt);
goto recurse;
case 'x': /* The date, using the locale's format. */
new_fmt =_ctloc(d_fmt);
recurse:
bp = (const u_char *)strptime((const char *)bp,
new_fmt, tm);
LEGAL_ALT(ALT_E);
continue;
/*
* "Elementary" conversion rules.
*/
case 'A': /* The day of week, using the locale's form. */
case 'a':
bp = find_string(bp, &tm->tm_wday, _ctloc(day),
_ctloc(abday), 7);
LEGAL_ALT(0);
continue;
case 'B': /* The month, using the locale's form. */
case 'b':
case 'h':
bp = find_string(bp, &tm->tm_mon, _ctloc(mon),
_ctloc(abmon), 12);
LEGAL_ALT(0);
continue;
case 'C': /* The century number. */
i = 20;
bp = conv_num(bp, &i, 0, 99);
i = i * 100 - TM_YEAR_BASE;
if (split_year)
i += tm->tm_year % 100;
split_year = 1;
tm->tm_year = i;
LEGAL_ALT(ALT_E);
continue;
case 'd': /* The day of month. */
case 'e':
bp = conv_num(bp, &tm->tm_mday, 1, 31);
LEGAL_ALT(ALT_O);
continue;
case 'k': /* The hour (24-hour clock representation). */
LEGAL_ALT(0);
/* FALLTHROUGH */
case 'H':
bp = conv_num(bp, &tm->tm_hour, 0, 23);
LEGAL_ALT(ALT_O);
continue;
case 'l': /* The hour (12-hour clock representation). */
LEGAL_ALT(0);
/* FALLTHROUGH */
case 'I':
bp = conv_num(bp, &tm->tm_hour, 1, 12);
if (tm->tm_hour == 12)
tm->tm_hour = 0;
LEGAL_ALT(ALT_O);
continue;
case 'j': /* The day of year. */
i = 1;
bp = conv_num(bp, &i, 1, 366);
tm->tm_yday = i - 1;
LEGAL_ALT(0);
continue;
case 'M': /* The minute. */
bp = conv_num(bp, &tm->tm_min, 0, 59);
LEGAL_ALT(ALT_O);
continue;
case 'm': /* The month. */
i = 1;
bp = conv_num(bp, &i, 1, 12);
tm->tm_mon = i - 1;
LEGAL_ALT(ALT_O);
continue;
case 'p': /* The locale's equivalent of AM/PM. */
bp = find_string(bp, &i, _ctloc(am_pm), NULL, 2);
if (tm->tm_hour > 11)
return NULL;
tm->tm_hour += i * 12;
LEGAL_ALT(0);
continue;
case 'S': /* The seconds. */
bp = conv_num(bp, &tm->tm_sec, 0, 61);
LEGAL_ALT(ALT_O);
continue;
case 'U': /* The week of year, beginning on sunday. */
case 'W': /* The week of year, beginning on monday. */
/*
* XXX This is bogus, as we can not assume any valid
* information present in the tm structure at this
* point to calculate a real value, so just check the
* range for now.
*/
bp = conv_num(bp, &i, 0, 53);
LEGAL_ALT(ALT_O);
continue;
case 'w': /* The day of week, beginning on sunday. */
bp = conv_num(bp, &tm->tm_wday, 0, 6);
LEGAL_ALT(ALT_O);
continue;
case 'Y': /* The year. */
i = TM_YEAR_BASE; /* just for data sanity... */
bp = conv_num(bp, &i, 0, 9999);
tm->tm_year = i - TM_YEAR_BASE;
LEGAL_ALT(ALT_E);
continue;
case 'y': /* The year within 100 years of the epoch. */
/* LEGAL_ALT(ALT_E | ALT_O); */
bp = conv_num(bp, &i, 0, 99);
if (split_year)
/* preserve century */
i += (tm->tm_year / 100) * 100;
else {
split_year = 1;
if (i <= 68)
i = i + 2000 - TM_YEAR_BASE;
else
i = i + 1900 - TM_YEAR_BASE;
}
tm->tm_year = i;
continue;
case 'Z':
tzset();
if (strncmp((const char *)bp, gmt, 3) == 0) {
tm->tm_isdst = 0;
#ifdef TM_GMTOFF
tm->TM_GMTOFF = 0;
#endif
#ifdef TM_ZONE
tm->TM_ZONE = gmt;
#endif
bp += 3;
} else {
const unsigned char *ep;
ep = find_string(bp, &i,
(const char * const *)tzname,
NULL, 2);
if (ep != NULL) {
tm->tm_isdst = i;
#ifdef TM_GMTOFF
tm->TM_GMTOFF = -(timezone);
#endif
#ifdef TM_ZONE
tm->TM_ZONE = tzname[i];
#endif
}
bp = ep;
}
continue;
/*
* Miscellaneous conversions.
*/
case 'n': /* Any kind of white-space. */
case 't':
while (isspace(*bp))
bp++;
LEGAL_ALT(0);
continue;
default: /* Unknown/unsupported conversion. */
return NULL;
}
}
return __UNCONST(bp);
}
static const u_char *
conv_num(const unsigned char *buf, int *dest, uint llim, uint ulim)
{
uint result = 0;
unsigned char ch;
/* The limit also determines the number of valid digits. */
uint rulim = ulim;
ch = *buf;
if (ch < '0' || ch > '9')
return NULL;
do {
result *= 10;
result += ch - '0';
rulim /= 10;
ch = *++buf;
} while ((result * 10 <= ulim) && rulim && ch >= '0' && ch <= '9');
if (result < llim || result > ulim)
return NULL;
*dest = result;
return buf;
}
static const u_char *
find_string(const u_char *bp, int *tgt, const char * const *n1,
const char * const *n2, int c)
{
int i;
unsigned int len;
/* check full name - then abbreviated ones */
for (; n1 != NULL; n1 = n2, n2 = NULL) {
for (i = 0; i < c; i++, n1++) {
len = strlen(*n1);
if (strncasecmp(*n1, (const char *)bp, len) == 0) {
*tgt = i;
return bp + len;
}
}
}
/* Nothing matched */
return NULL;
}