strftime: Add support for %s (seconds since epoch)

* libc/time/strftime.c (__strftime): add support for %s (seconds from
	Unix epoch).  Fix whitespaces.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

newlib/ChangeLog

@@ -1,3 +1,8 @@
+2015-10-26  Brian Inglis  <Brian.Inglis@SystematicSw.ab.ca>
+
+	* libc/time/strftime.c (__strftime): add support for %s (seconds from
+	Unix epoch).  Fix whitespaces.
+
 2015-10-19  Nick Clifton  <nickc@redhat.com>
 
 	* libc/include/sys/_intsup.h: Add support for 16-bit and 20-bit

newlib/libc/time/strftime.c

@@ -166,6 +166,10 @@ notations, the result is an empty string. [tm_sec, tm_min, tm_hour]
 o %R
 The 24-hour time, to the minute.  Equivalent to "%H:%M". [tm_min, tm_hour]
 
+o %s
+The time elapsed, in seconds, since the start of the Unix epoch at
+1970-01-01 00:00:00 UTC.
+
 o %S
 The second, formatted with two digits (from `<<00>>' to `<<60>>').  The
 value 60 accounts for the occasional leap second. [tm_sec]
@@ -1109,6 +1113,74 @@ recurse:
 			  tim_p->tm_hour, tim_p->tm_min);
           CHECK_LENGTH ();
           break;
+	case CQ('s'):
+/*
+ * From:
+ * The Open Group Base Specifications Issue 7
+ * IEEE Std 1003.1, 2013 Edition
+ * Copyright (c) 2001-2013 The IEEE and The Open Group
+ * XBD Base Definitions
+ * 4. General Concepts
+ * 4.15 Seconds Since the Epoch
+ * A value that approximates the number of seconds that have elapsed since the
+ * Epoch. A Coordinated Universal Time name (specified in terms of seconds
+ * (tm_sec), minutes (tm_min), hours (tm_hour), days since January 1 of the year
+ * (tm_yday), and calendar year minus 1900 (tm_year)) is related to a time
+ * represented as seconds since the Epoch, according to the expression below.
+ * If the year is <1970 or the value is negative, the relationship is undefined.
+ * If the year is >=1970 and the value is non-negative, the value is related to a
+ * Coordinated Universal Time name according to the C-language expression, where
+ * tm_sec, tm_min, tm_hour, tm_yday, and tm_year are all integer types:
+ * tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
+ *     (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
+ *     ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
+ * OR
+ * ((((tm_year-69)/4 - (tm_year-1)/100 + (tm_year+299)/400 +
+ *         (tm_year-70)*365 + tm_yday)*24 + tm_hour)*60 + tm_min)*60 + tm_sec
+ */
+/* modified from %z case by hoisting offset outside if block and initializing */
+	  {
+	    long offset = 0;	/* offset < 0 => W of GMT, > 0 => E of GMT:
+				   subtract to get UTC */
+
+	    if (tim_p->tm_isdst >= 0)
+	      {
+		TZ_LOCK;
+		if (!tzset_called)
+		  {
+		    _tzset_unlocked ();
+		    tzset_called = 1;
+		  }
+
+#if defined (__CYGWIN__)
+		/* Cygwin must check if the application has been built with or
+		   without the extra tm members for backward compatibility, and
+		   then use either that or the old method fetching from tzinfo.
+		   Rather than pulling in the version check infrastructure, we
+		   just call a Cygwin function. */
+		extern long __cygwin_gettzoffset (const struct tm *tmp);
+		offset = __cygwin_gettzoffset (tim_p);
+#elif defined (__TM_GMTOFF)
+		offset = tim_p->__TM_GMTOFF;
+#else
+		__tzinfo_type *tz = __gettzinfo ();
+		/* The sign of this is exactly opposite the envvar TZ.  We
+		   could directly use the global _timezone for tm_isdst==0,
+		   but have to use __tzrule for daylight savings.  */
+		offset = -tz->__tzrule[tim_p->tm_isdst > 0].offset;
+#endif
+		TZ_UNLOCK;
+	      }
+	    len = snprintf (&s[count], maxsize - count, CQ("%lld"),
+			    (((((long long)tim_p->tm_year - 69)/4
+				- (tim_p->tm_year - 1)/100
+				+ (tim_p->tm_year + 299)/400
+				+ (tim_p->tm_year - 70)*365 + tim_p->tm_yday)*24
+			      + tim_p->tm_hour)*60 + tim_p->tm_min)*60
+			    + tim_p->tm_sec - offset);
+	    CHECK_LENGTH ();
+	  }
+          break;
 	case CQ('S'):
 #ifdef _WANT_C99_TIME_FORMATS
 	  if (alt != CQ('O') || !*alt_digits
@@ -1442,6 +1514,7 @@ const struct test  Vec0[] = {
 	{ CQ("%p"), 2+1, EXP(CQ("AM")) },
 	{ CQ("%r"), 11+1, EXP(CQ("09:53:47 AM")) },
 	{ CQ("%R"), 5+1, EXP(CQ("09:53")) },
+	{ CQ("%s"), 2+1, EXP(CQ("1230648827")) },
 	{ CQ("%S"), 2+1, EXP(CQ("47")) },
 	{ CQ("%t"), 1+1, EXP(CQ("\t")) },
 	{ CQ("%T"), 8+1, EXP(CQ("09:53:47")) },
@@ -1502,6 +1575,7 @@ const struct test  Vec1[] = {
 	{ CQ("%p"), 2+1, EXP(CQ("PM")) },
 	{ CQ("%r"), 11+1, EXP(CQ("11:01:13 PM")) },
 	{ CQ("%R"), 5+1, EXP(CQ("23:01")) },
+	{ CQ("%s"), 2+1, EXP(CQ("1215054073")) },
 	{ CQ("%S"), 2+1, EXP(CQ("13")) },
 	{ CQ("%t"), 1+1, EXP(CQ("\t")) },
 	{ CQ("%T"), 8+1, EXP(CQ("23:01:13")) },

winsup/cygwin/release/2.3.0

@@ -1,6 +1,8 @@
 What's new:
 -----------
 
+- strftime(3) supports %s (seconds since Epoch) now.
+
 - posix_madvise(POSIX_MADV_WILLNEED) now utilizes OS functionality available
   starting with Windows 8/Server 2012.  Still a no-op on older systems.
 

winsup/doc/ChangeLog

@@ -1,3 +1,7 @@
+2015-10-27  Corinna Vinschen  <corinna@vinschen.de>
+
+	* new-features.xml (ov-new2.3): Document strftime %s addition.
+
 2015-10-22  Corinna Vinschen  <corinna@vinschen.de>
 
 	* posix.xml (std-iso): New section.

winsup/doc/new-features.xml

@@ -8,6 +8,10 @@
 
 <itemizedlist mark="bullet">
 
+<listitem><para>
+strftime(3) supports %s (seconds since Epoch) now.
+</para></listitem>
+
 <listitem><para>
 posix_madvise(POSIX_MADV_WILLNEED) now utilizes OS functionality available
 starting with Windows 8/Server 2012.