Speed up DateTime members, by caching the results.

Speed up DateTime members, by caching the results.

The result is stored in a list of ints. This turned out to be the most efficient way to store it, compared to packing in ints.

BUG=
R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=35303

[Anders Johnsen, 2014-04-22 13:37:53]

This speeds up the following:

import 'dart:io';

void main() {
  var date = new DateTime.now();
  for (int i = 0; i < 100000; i++) {
    HttpDate.format(date);
  }
  var sw = new Stopwatch()..start();
  for (int i = 0; i < 1000000; i++) {
    HttpDate.format(date);
  }
  print(sw.elapsedMicroseconds / 1000000);
}


from 2.122s

to 1.411s

[srdjan, 2014-04-22 19:55:46]

lgtm

https://codereview.chromium.org/247373004/diff/20001/runtime/lib/date_patch.dart
File runtime/lib/date_patch.dart (right):

https://codereview.chromium.org/247373004/diff/20001/runtime/lib/date_patch.d...
runtime/lib/date_patch.dart:150: return _parts[_MILLISECOND_INDEX];
You could write:

 int get millisecond =>  _parts[_MILLISECOND_INDEX];
....

get _parts {
  if (__parts == null) { __parts = _computeUpperPart(_localDateInUtcMs); }
  return __parts;
}

[Anders Johnsen, 2014-04-23 05:58:54]

https://codereview.chromium.org/247373004/diff/20001/runtime/lib/date_patch.dart
File runtime/lib/date_patch.dart (right):

https://codereview.chromium.org/247373004/diff/20001/runtime/lib/date_patch.d...
runtime/lib/date_patch.dart:150: return _parts[_MILLISECOND_INDEX];
On 2014/04/22 19:55:46, srdjan wrote:
> You could write:
> 
>  int get millisecond =>  _parts[_MILLISECOND_INDEX];
> ....
> 
> get _parts {
>   if (__parts == null) { __parts = _computeUpperPart(_localDateInUtcMs); }
>   return __parts;
> }

Done.

[Anders Johnsen, 2014-04-23 06:17:45]

Committed patchset #3 manually as r35303 (presubmit successful).