Rewrite MakeDay function from JS to C++.

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 3986)
+++ src/runtime.cc	(working copy)
@@ -4930,6 +4930,38 @@
 }
 
 
+static Object* Runtime_DateMakeDay(Arguments args) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 3);
+
+  CONVERT_SMI_CHECKED(year, args[0]);
+  CONVERT_SMI_CHECKED(month, args[1]);
+  CONVERT_SMI_CHECKED(date, args[2]);
+
+  static const int day_from_month[] = {0, 31, 59, 90, 120, 151,
+                                       181, 212, 243, 273, 304, 334};
+  static const int day_from_month_leap[] = {0, 31, 60, 91, 121, 152,
+                                            182, 213, 244, 274, 305, 335};
+
+  year += month / 12;
+  month %= 12;
+  if (month < 0) {
+    year--;
+    month += 12;
+  }
+
+  static const int base_day = 365*1970 + 1969/4 - 1969/100 + 1969/400;
+
+  int day_from_year = 365*year + (year - 1)/4 - (year - 1)/100 + (year - 1)/400 - base_day;

[Mads Ager (chromium), 2010/03/02 13:04:08]

Line too long, please reformat.  Also, please have a space around arithmetic
operations and use parenthesis to make the precedence explicit.

[Oleg Eterevsky, 2010/03/02 13:28:23]

I tried to reformat it to make it more readable, avoiding extra parentheses.
Hope, it's ok now.

On 2010/03/02 13:04:08, Mads Ager wrote:

+
+  if (year % 4 || (year % 100 == 0 && year % 400 != 0)) {
+    return Smi::FromInt(day_from_year + day_from_month[month] + date - 1);
+  } else {
+    return Smi::FromInt(day_from_year + day_from_month_leap[month] + date - 1);
+  }
+}
+
+
 static Object* Runtime_NewArgumentsFast(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 3);