/*

 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")

 *

 * SPDX-License-Identifier: MPL-2.0 AND BSD-2-Clause

 *

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, you can obtain one at https://mozilla.org/MPL/2.0/.

 *

 * See the COPYRIGHT file distributed with this work for additional

 * information regarding copyright ownership.

 */

/*-

 * 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 <ctype.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.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)) != 0) \

      return ((0));         \

  }

#ifndef TM_YEAR_BASE

#define TM_YEAR_BASE 1900

#endif /* ifndef TM_YEAR_BASE */

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 (!isdigit((unsigned char)**buf)) {

    return 0;

  }

  do {

    result = 10 * result + *(*buf)++ - '0';

    rulim /= 10;

  } while ((result * 10 <= ulim) && rulim &&

     isdigit((unsigned char)**buf));

  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;

  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 */

  return UNCONST(bp);

}