push some date functions in the lib-lib.

[apps/madmutt.git] / lib-lib / date.c

diff --git a/lib-lib/date.c b/lib-lib/date.c
new file mode 100644 (file)
index 0000000..4bc6873
--- /dev/null
+++ b/lib-lib/date.c
@@ -0,0 +1,188 @@
+/*
+ *  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++;
+        }
+    }
+}