Changeset 20203 in webkit for trunk/JavaScriptCore/kjs

Timestamp:

Mar 14, 2007, 7:21:47 PM (18 years ago)

Author:

kmccullo

Message:

JavaScriptCore:

Reviewed by Geoff.

• rdar://problem/5045720
• DST changes in US affect JavaScript date calculations (12975) This fix was to ensure we properly test for the new changes to DST in the US. Also this fixes when we apply DST, now we correctly map most past years to current DST rules. We still have a small issue with years before 1900 or after 2100. rdar://problem/5055038

• kjs/DateMath.cpp: Fix DST to match spec better. (KJS::getCurrentUTCTime): (KJS::mimimumYearForDST): (KJS::maximumYearForDST): (KJS::equivalentYearForDST): (KJS::getDSTOffset):
• kjs/DateMath.h: Consolodated common funtionality.
• kjs/date_object.cpp: Consolodated common functionality. (KJS::formatLocaleDate): (KJS::DateObjectImp::construct):
• tests/mozilla/ecma/jsref.js: Added functions for finding the correct days when DST starts and ends.
• tests/mozilla/ecma/shell.js: Added back in the old DST functions for ease of merging with mozilla if needed.
• tests/mozilla/ecma_2/jsref.js: Added functions for finding the correct days when DST starts and ends.
• tests/mozilla/ecma_3/Date/shell.js: Added functions for finding the correct days when DST starts and ends.
• tests/mozilla/expected.html: Updated to show all date tests passing.

LayoutTests:

Reviewed by Geoff.

• rdar://problem/5045720
• DST changes in US affect JavaScript date calculations (12975) Changed layout tests to properly check for the new changes to DST in the US. Also these now test that equivalent years return the same results for DST.

• fast/js/date-DST-time-cusps-expected.txt:
• fast/js/date-big-setdate-expected.txt:
• fast/js/resources/date-DST-time-cusps.js:
• fast/js/resources/date-big-setdate.js:

Location:

trunk/JavaScriptCore/kjs

Files:

• DateMath.cpp (modified) (3 diffs)
• DateMath.h (modified) (1 diff)

trunk/JavaScriptCore/kjs/DateMath.cpp

@@ -45 +45 @@
 #include <math.h>
 #include <stdint.h>
+#include <value.h>
+
+#include <wtf/Assertions.h>
 
 #if PLATFORM(DARWIN)
@@ -268 +271 @@
 }
 
+double getCurrentUTCTime()
+{
+#if PLATFORM(WIN_OS)
+#if COMPILER(BORLAND)
+    struct timeb timebuffer;
+    ftime(&timebuffer);
+#else
+    struct _timeb timebuffer;
+    _ftime(&timebuffer);
+#endif
+    double utc = timebuffer.time * msPerSecond + timebuffer.millitm;
+#else
+    struct timeval tv;
+    gettimeofday(&tv, 0);
+    double utc = floor(tv.tv_sec * msPerSecond + tv.tv_usec / 1000);
+#endif
+    return utc;
+}
+
+// There is a hard limit at 2038 that we currently do not have a workaround
+// for (rdar://problem/5052975).
+static inline int maximumYearForDST()
+{
+    return 2037;
+}
+
+// It is ok if the cached year is not the current year (e.g. Dec 31st)
+// so long as the rules for DST did not change between the two years, if it does
+// the app would need to be restarted.
+static int mimimumYearForDST()
+{
+    // Because of the 2038 issue (see maximumYearForDST) if the current year is
+    // greater than the max year minus 27 (2010), we want to use the max year
+    // minus 27 instead, to ensure there is a range of 28 years that all years
+    // can map to.
+    static int minYear = std::min(msToYear(getCurrentUTCTime()), maximumYearForDST()-27) ;
+    return minYear;
+}
+
 /*
- * Find a year for which any given date will fall on the same weekday.
- *
- * This function should be used with caution when used other than
- * for determining DST; it hasn't been proven not to produce an
- * incorrect year for times near year boundaries.
+ * Find an equivalent year for the one given, where equivalence is deterined by
+ * the two years having the same leapness and the first day of the year, falling
+ * on the same day of the week.
+ *
+ * This function returns a year between this current year and 2037, however this
+ * function will potentially return incorrect results if the current year is after
+ * 2010, (rdar://problem/5052975), if the year passed in is before 1900 or after
+ * 2100, (rdar://problem/5055038).
  */
 int equivalentYearForDST(int year)
 {
-    int difference = 2000 - year;   // Arbitrary year around which most dates equivalence is correct
-    int quotient = difference / 28; // Integer division, no remainder.
-    int product = quotient * 28;
-    return year + product;
+    static int minYear = mimimumYearForDST();
+    static int maxYear = maximumYearForDST();
+    
+    int difference;
+    if (year > maxYear)
+        difference = minYear - year;
+    else if (year < minYear)
+        difference = maxYear - year;
+    else
+        return year;
+
+    int quotient = difference / 28;
+    int product = (quotient) * 28;
+
+    year += product;
+    ASSERT((year >= minYear && year <= maxYear) || (product - year == static_cast<int>(NaN)));
+    return year;
 }
 
@@ -377 +435 @@
     // determining DST. For this reason we shift away from years that localtime can handle but would
     // return historically accurate information.
-
-    // if before Jan 01, 2000 12:00:00 AM UTC or after Jan 01, 2038 12:00:00 AM UTC
-    if (ms < 946684800000.0 || ms > 2145916800000.0) {
-        int year = equivalentYearForDST(msToYear(ms));
-        int day = dateToDayInYear(year, msToMonth(ms), msToDayInMonth(ms));
+    int year = msToYear(ms);
+    int equvalentYear = equivalentYearForDST(year);
+    if (year != equvalentYear) {
+        int day = dateToDayInYear(equvalentYear, msToMonth(ms), msToDayInMonth(ms));
         ms = (day * msPerDay) + msToMilliseconds(ms);
     }

trunk/JavaScriptCore/kjs/DateMath.h

@@ -54 +54 @@
 double getUTCOffset();
 int equivalentYearForDST(int year);
+double getCurrentUTCTime();
 
 const char * const weekdayName[7] = { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" };