From e63b2f75607905fedf00cfd9fe644b26af715ffd Mon Sep 17 00:00:00 2001
From: Leo C
Date: Mon, 1 Dec 2014 23:25:55 +0100
Subject: switch to avr-libc 1.8.1 time library

---
 time/iso_week_date_r.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 time/iso_week_date_r.c

(limited to 'time/iso_week_date_r.c')

diff --git a/time/iso_week_date_r.c b/time/iso_week_date_r.c
new file mode 100644
index 0000000..ac1feb4
--- /dev/null
+++ b/time/iso_week_date_r.c
@@ -0,0 +1,114 @@
+/*
+ * (c)2012 Michael Duane Rice All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer. 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. Neither the name of the copyright holders
+ * nor the names of contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
+ */
+
+/* $Id: iso_week_date_r.c 2394 2013-05-04 10:26:24Z swfltek $ */
+
+/*
+    Compute the ISO 8601 week date corresponding to the given year and day of year.
+    See http://en.wikipedia.org/wiki/ISO_week_date for a full description. To summarize:
+
+        Weeks are numbered from 1 to 53.
+        Week days are numbered 1 to 7, beginning with Monday as day 1.
+
+        The first week of the year contains the first Thursday in that year.
+        Dates prior to week 1 belong to the final week of the previous year.
+
+        The final week of the year contains the last Thursday in that year.
+        Dates after the final week belong to week 1 of the following year.
+
+*/
+
+#include <time.h>
+
+void
+iso_week_date_r(int y, int yday, struct week_date * iso)
+{
+    uint16_t        years, n, wday;
+    int             weeknum;
+    int isLeap;
+
+    iso->year = y;
+
+    isLeap = is_leap_year(y);
+
+    /* compute days elapsed since epoch */
+    years = y - 2000;
+    n = 365 * years + yday;
+    if (years) {
+        n++;        /* epoch was a leap year */
+        n += years / 4;
+        n -= isLeap;
+        if (years > 100)
+            n--;
+    }
+
+    /* compute ISO8601 day of week (1 ... 7, Monday = 1) */
+    wday = n + 6; /* epoch was a Saturday */
+    wday %= 7;
+    if (wday == 0)
+        wday = 7;
+
+    iso->day = wday;
+
+    /* compute tentative week number */
+    weeknum = yday + 11 - wday;
+    weeknum /= 7;
+
+    /* if 53, it could be week 1 of the following year */
+    if (weeknum == 53) {
+        /*
+            The final week must include its Thursday in the year. We determine the yday of this
+            weeks Thursday, and test whether it exceeds this years length.
+        */
+
+        /* determine final yday of this year, 364 or 365 */
+        n = 364 + isLeap;
+
+        /* compute yday of this weeks Thursday */
+        wday--;       /* convert to zero based week, Monday = 0 */
+        yday -= wday; /* yday of this weeks Monday */
+        yday += 3;    /* yday of this weeks Thursday */
+
+        /* Is this weeks Thursday included in the year? */
+        if (yday > (int) n) {
+            iso->year++;
+            weeknum = 1;
+        }
+    }
+    iso->week = weeknum;
+
+    /*
+        If zero, it is the final week of the previous year.
+        We determine that by asking for the week number of Dec 31.
+    */
+    if (weeknum == 0) {
+        y = y - 1;
+        iso_week_date_r(y, 364 + is_leap_year(y), iso);
+        iso->day = wday;
+    }
+}
-- 
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