+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ *
+ * Copyright © 2006 Pierre Habouzit
+ */
+
+/*
+ * Copyright notice from original mutt:
+ * Copyright (C) 1996-2000 Michael R. Elkins <me@mutt.org>
+ *
+ * This file is part of mutt-ng, see http://www.muttng.org/.
+ * It's licensed under the GNU General Public License,
+ * please see the file GPL in the top level source directory.
+ */
+
+#include "date.h"
+
+/* returns the seconds east of UTC given `g' and its corresponding gmtime()
+ representation */
+static time_t compute_tz(time_t g, struct tm *utc)
+{
+ struct tm *lt = localtime (&g);
+ time_t t;
+ int yday;
+
+ t = (lt->tm_hour - utc->tm_hour) * 3600
+ + (lt->tm_min - utc->tm_min) * 60;
+ yday = (lt->tm_yday - utc->tm_yday);
+
+ if (yday) {
+ /* This code is optimized to negative timezones (West of Greenwich) */
+ if (yday == -1 || /* UTC passed midnight before localtime */
+ yday > 1) /* UTC passed new year before localtime */
+ t -= 24 * 60 * 60;
+ else
+ t += 24 * 60 * 60;
+ }
+
+ return t;
+}
+
+/* Returns the local timezone in seconds east of UTC for the time t,
+ or for the current time if t is zero. */
+time_t mutt_local_tz(time_t t)
+{
+ struct tm *ptm;
+ struct tm utc;
+
+ if (!t)
+ t = time(NULL);
+
+ /* need to make a copy because gmtime/localtime return a pointer to
+ static memory (grr!) */
+ ptm = gmtime(&t);
+ utc = *ptm;
+ return compute_tz(t, &utc);
+}
+
+/* converts struct tm to time_t, but does not take the local timezone into
+ account unless ``local'' is nonzero */
+time_t mutt_mktime(struct tm *t, int local)
+{
+ static short const AccumDaysPerMonth[12] = {
+ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+ };
+
+ time_t g;
+
+ /* Compute the number of days since January 1 in the same year */
+ g = AccumDaysPerMonth[t->tm_mon % 12];
+
+ /* The leap years are 1972 and every 4. year until 2096,
+ * but this algoritm will fail after year 2099 */
+ g += t->tm_mday;
+ if ((t->tm_year % 4) || t->tm_mon < 2)
+ g--;
+ t->tm_yday = g;
+
+ /* Compute the number of days since January 1, 1970 */
+ g += (t->tm_year - 70) * 365;
+ g += (t->tm_year - 69) / 4;
+
+ /* Compute the number of hours */
+ g *= 24;
+ g += t->tm_hour;
+
+ /* Compute the number of minutes */
+ g *= 60;
+ g += t->tm_min;
+
+ /* Compute the number of seconds */
+ g *= 60;
+ g += t->tm_sec;
+
+ if (local)
+ g -= compute_tz(g, t);
+
+ return g;
+}
+
+/* Return 1 if month is February of leap year, else 0 */
+__attribute__((const))
+static int isLeapYearFeb(int m, int y)
+{
+ return (m == 1) /* february ? */
+ && !(y & 3) /* multiple of 4 ? */
+ && ((y % 100) || !((y + 1900) % 400));
+ /* !multiple of 100, or multiple of 400 */
+}
+
+__attribute__((const))
+static inline int nbDaysInMonth(int m, int y)
+{
+ static char const DaysPerMonth[12] = {
+ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+ };
+
+ return DaysPerMonth[m] + isLeapYearFeb(m, y);
+}
+
+void mutt_normalize_time(struct tm *tm)
+{
+ while (tm->tm_sec < 0) {
+ tm->tm_sec += 60;
+ tm->tm_min--;
+ }
+ while (tm->tm_sec >= 60) {
+ tm->tm_sec -= 60;
+ tm->tm_min++;
+ }
+ while (tm->tm_min < 0) {
+ tm->tm_min += 60;
+ tm->tm_hour--;
+ }
+ while (tm->tm_min >= 60) {
+ tm->tm_min -= 60;
+ tm->tm_hour++;
+ }
+ while (tm->tm_hour < 0) {
+ tm->tm_hour += 24;
+ tm->tm_mday--;
+ }
+ while (tm->tm_hour >= 24) {
+ tm->tm_hour -= 24;
+ tm->tm_mday++;
+ }
+ /* use loops on NNNdwmy user input values? */
+ while (tm->tm_mon < 0) {
+ tm->tm_mon += 12;
+ tm->tm_year--;
+ }
+ while (tm->tm_mon >= 12) {
+ tm->tm_mon -= 12;
+ tm->tm_year++;
+ }
+ while (tm->tm_mday <= 0) {
+ if (tm->tm_mon) {
+ tm->tm_mon--;
+ } else {
+ tm->tm_mon = 11;
+ tm->tm_year--;
+ }
+ tm->tm_mday += nbDaysInMonth(tm->tm_mon, tm->tm_year);
+ }
+
+ while (tm->tm_mday > nbDaysInMonth(tm->tm_mon, tm->tm_year)) {
+ tm->tm_mday -= nbDaysInMonth(tm->tm_mon, tm->tm_year);
+ if (tm->tm_mon < 11) {
+ tm->tm_mon++;
+ } else {
+ tm->tm_mon = 0;
+ tm->tm_year++;
+ }
+ }
+}