tm.c

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/*
 * Copyright (C) 2014  Internet Systems Consortium, Inc. ("ISC")
 *
 * 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC 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.
 */

/*-
 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code was contributed to The NetBSD Foundation by Klaus Klein.
 *
 * 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 <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <ctype.h>

#include <isc/tm.h>
#include <isc/util.h>

/*
 * Portable conversion routines for struct tm, replacing
 * timegm() and strptime(), which are not available on all
 * platforms and don't always behave the same way when they
 * are.
 */

/*
 * 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 (0); }

#ifndef TM_YEAR_BASE
#define TM_YEAR_BASE 1900
#endif

static const char *day[7] = {
        "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
        "Friday", "Saturday"
};
static const char *abday[7] = {
        "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};
static const char *mon[12] = {
        "January", "February", "March", "April", "May", "June", "July",
        "August", "September", "October", "November", "December"
};
static const char *abmon[12] = {
        "Jan", "Feb", "Mar", "Apr", "May", "Jun",
        "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
static const char *am_pm[2] = {
        "AM", "PM"
};

static int
conv_num(const char **buf, int *dest, int llim, int ulim) {
        int result = 0;

        /* The limit also determines the number of valid digits. */
        int rulim = ulim;

        if (**buf < '0' || **buf > '9')
                return (0);

        do {
                result *= 10;
                result += *(*buf)++ - '0';
                rulim /= 10;
        } while ((result * 10 <= ulim) &&
                 rulim && **buf >= '0' && **buf <= '9');

        if (result < llim || result > ulim)
                return (0);

        *dest = result;
        return (1);
}

time_t
isc_tm_timegm(struct tm *tm) {
        time_t ret;
        int i, yday = 0, leapday;
        int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30 };

        leapday = ((((tm->tm_year + 1900 ) % 4) == 0 &&
                    ((tm->tm_year + 1900 ) % 100) != 0) ||
                   ((tm->tm_year + 1900 ) % 400) == 0) ? 1 : 0;
        mdays[1] += leapday;

        yday = tm->tm_mday - 1;
        for (i = 1; i <= tm->tm_mon; i++)
                yday += mdays[i - 1];
        ret = tm->tm_sec +
              (60 * tm->tm_min) +
              (3600 * tm->tm_hour) +
              (86400 * (yday +
                       ((tm->tm_year - 70) * 365) +
                       ((tm->tm_year - 69) / 4) -
                       ((tm->tm_year - 1) / 100) +
                       ((tm->tm_year + 299) / 400)));
        return (ret);
}

char *
isc_tm_strptime(const char *buf, const char *fmt, struct tm *tm) {
        char c, *ret;
        const char *bp;
        size_t len = 0;
        int alt_format, i, split_year = 0;

        REQUIRE(buf != NULL);
        REQUIRE(fmt != NULL);
        REQUIRE(tm != NULL);

        memset(tm, 0, sizeof(struct tm));

        bp = buf;

        while ((c = *fmt) != '\0') {
                /* Clear `alternate' modifier prior to new conversion. */
                alt_format = 0;

                /* Eat up white-space. */
                if (isspace((unsigned char) c)) {
                        while (isspace((unsigned char) *bp))
                                bp++;

                        fmt++;
                        continue;
                }

                if ((c = *fmt++) != '%')
                        goto literal;


again:          switch (c = *fmt++) {
                case '%':       /* "%%" is converted to "%". */
literal:
                        if (c != *bp++)
                                return (0);
                        break;

                /*
                 * "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. */
                        LEGAL_ALT(ALT_E);
                        if (!(bp = isc_tm_strptime(bp, "%x %X", tm)))
                                return (0);
                        break;

                case 'D':       /* The date as "%m/%d/%y". */
                        LEGAL_ALT(0);
                        if (!(bp = isc_tm_strptime(bp, "%m/%d/%y", tm)))
                                return (0);
                        break;

                case 'R':       /* The time as "%H:%M". */
                        LEGAL_ALT(0);
                        if (!(bp = isc_tm_strptime(bp, "%H:%M", tm)))
                                return (0);
                        break;

                case 'r':       /* The time in 12-hour clock representation. */
                        LEGAL_ALT(0);
                        if (!(bp = isc_tm_strptime(bp, "%I:%M:%S %p", tm)))
                                return (0);
                        break;

                case 'T':       /* The time as "%H:%M:%S". */
                        LEGAL_ALT(0);
                        if (!(bp = isc_tm_strptime(bp, "%H:%M:%S", tm)))
                                return (0);
                        break;

                case 'X':       /* The time, using the locale's format. */
                        LEGAL_ALT(ALT_E);
                        if (!(bp = isc_tm_strptime(bp, "%H:%M:%S", tm)))
                                return (0);
                        break;

                case 'x':       /* The date, using the locale's format. */
                        LEGAL_ALT(ALT_E);
                        if (!(bp = isc_tm_strptime(bp, "%m/%d/%y", tm)))
                                return (0);
                        break;

                /*
                 * "Elementary" conversion rules.
                 */
                case 'A':       /* The day of week, using the locale's form. */
                case 'a':
                        LEGAL_ALT(0);
                        for (i = 0; i < 7; i++) {
                                /* Full name. */
                                len = strlen(day[i]);
                                if (strncasecmp(day[i], bp, len) == 0)
                                        break;

                                /* Abbreviated name. */
                                len = strlen(abday[i]);
                                if (strncasecmp(abday[i], bp, len) == 0)
                                        break;
                        }

                        /* Nothing matched. */
                        if (i == 7)
                                return (0);

                        tm->tm_wday = i;
                        bp += len;
                        break;

                case 'B':       /* The month, using the locale's form. */
                case 'b':
                case 'h':
                        LEGAL_ALT(0);
                        for (i = 0; i < 12; i++) {
                                /* Full name. */
                                len = strlen(mon[i]);
                                if (strncasecmp(mon[i], bp, len) == 0)
                                        break;

                                /* Abbreviated name. */
                                len = strlen(abmon[i]);
                                if (strncasecmp(abmon[i], bp, len) == 0)
                                        break;
                        }

                        /* Nothing matched. */
                        if (i == 12)
                                return (0);

                        tm->tm_mon = i;
                        bp += len;
                        break;

                case 'C':       /* The century number. */
                        LEGAL_ALT(ALT_E);
                        if (!(conv_num(&bp, &i, 0, 99)))
                                return (0);

                        if (split_year) {
                                tm->tm_year = (tm->tm_year % 100) + (i * 100);
                        } else {
                                tm->tm_year = i * 100;
                                split_year = 1;
                        }
                        break;

                case 'd':       /* The day of month. */
                case 'e':
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_mday, 1, 31)))
                                return (0);
                        break;

                case 'k':       /* The hour (24-hour clock representation). */
                        LEGAL_ALT(0);
                        /* FALLTHROUGH */
                case 'H':
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_hour, 0, 23)))
                                return (0);
                        break;

                case 'l':       /* The hour (12-hour clock representation). */
                        LEGAL_ALT(0);
                        /* FALLTHROUGH */
                case 'I':
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_hour, 1, 12)))
                                return (0);
                        if (tm->tm_hour == 12)
                                tm->tm_hour = 0;
                        break;

                case 'j':       /* The day of year. */
                        LEGAL_ALT(0);
                        if (!(conv_num(&bp, &i, 1, 366)))
                                return (0);
                        tm->tm_yday = i - 1;
                        break;

                case 'M':       /* The minute. */
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_min, 0, 59)))
                                return (0);
                        break;

                case 'm':       /* The month. */
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &i, 1, 12)))
                                return (0);
                        tm->tm_mon = i - 1;
                        break;

                case 'p':       /* The locale's equivalent of AM/PM. */
                        LEGAL_ALT(0);
                        /* AM? */
                        if (strcasecmp(am_pm[0], bp) == 0) {
                                if (tm->tm_hour > 11)
                                        return (0);

                                bp += strlen(am_pm[0]);
                                break;
                        }
                        /* PM? */
                        else if (strcasecmp(am_pm[1], bp) == 0) {
                                if (tm->tm_hour > 11)
                                        return (0);

                                tm->tm_hour += 12;
                                bp += strlen(am_pm[1]);
                                break;
                        }

                        /* Nothing matched. */
                        return (0);

                case 'S':       /* The seconds. */
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_sec, 0, 61)))
                                return (0);
                        break;

                case 'U':       /* The week of year, beginning on sunday. */
                case 'W':       /* The week of year, beginning on monday. */
                        LEGAL_ALT(ALT_O);
                        /*
                         * 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.
                         */
                         if (!(conv_num(&bp, &i, 0, 53)))
                                return (0);
                         break;

                case 'w':       /* The day of week, beginning on sunday. */
                        LEGAL_ALT(ALT_O);
                        if (!(conv_num(&bp, &tm->tm_wday, 0, 6)))
                                return (0);
                        break;

                case 'Y':       /* The year. */
                        LEGAL_ALT(ALT_E);
                        if (!(conv_num(&bp, &i, 0, 9999)))
                                return (0);

                        tm->tm_year = i - TM_YEAR_BASE;
                        break;

                case 'y':       /* The year within 100 years of the epoch. */
                        LEGAL_ALT(ALT_E | ALT_O);
                        if (!(conv_num(&bp, &i, 0, 99)))
                                return (0);

                        if (split_year) {
                                tm->tm_year = ((tm->tm_year / 100) * 100) + i;
                                break;
                        }
                        split_year = 1;
                        if (i <= 68)
                                tm->tm_year = i + 2000 - TM_YEAR_BASE;
                        else
                                tm->tm_year = i + 1900 - TM_YEAR_BASE;
                        break;

                /*
                 * Miscellaneous conversions.
                 */
                case 'n':       /* Any kind of white-space. */
                case 't':
                        LEGAL_ALT(0);
                        while (isspace((unsigned char) *bp))
                                bp++;
                        break;


                default:        /* Unknown/unsupported conversion. */
                        return (0);
                }


        }

        /* LINTED functional specification */
        DE_CONST(bp, ret);
        return (ret);
}

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