Fix bug in DateTime.parse.

sdk/lib/core/date_time.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.core;
 
 /**
  * An instant in time, such as July 20, 1969, 8:18pm GMT.
  *
  * Create a DateTime object by using one of the constructors
@@ skipping 197 matching lines @@
    * * An optional time part, separated from the date by either `T` or a space.
    *   The time part is a two digit hour,
    *   then optionally a two digit minutes value,
    *   then optionally a two digit seconds value, and
    *   then optionally a '.' followed by a one-to-six digit second fraction.
    *   The minuts and seconds may be separated from the previous parts by a ':'.
    *   Examples: "12", "12:30:24.124", "123010.50".
    * * An optional time-zone offset part,
    *   possibly separated from the previous by a space.
    *   The time zone is either 'z' or 'Z', or it is a signed two digit hour
-   *   part and an optional two digit minute part.
+   *   part and an optional two digit minute part. The sign must be either
+   *   "+" or "-", and can not be omitted.
    *   The minutes may be separted from the hours by a ':'.
    *   Examples: "Z", "-10", "01:30", "1130".
    *
    * This includes the output of both [toString] and [toIso8601String], which
    * will be parsed back into a `DateTime` object with the same time as the
    * original.
    *
    * The result is always in either local time or UTC.
    * If a time zone offset other than UTC is specified,
    * the time is converted to the equivalent UTC time.
@@ skipping 26 matching lines @@
      * time_opt ::= <empty> | (' ' | 'T') hour minutes_opt
      * minutes_opt ::= <empty> | colon_opt digit{2} seconds_opt
      * seconds_opt ::= <empty> | colon_opt digit{2} millis_opt
      * millis_opt ::= <empty> | '.' digit{1,6}
      * timezone_opt ::= <empty> | space_opt timezone
      * space_opt :: ' ' | <empty>
      * timezone ::= 'z' | 'Z' | sign digit{2} timezonemins_opt
      * timezonemins_opt ::= <empty> | colon_opt digit{2}
      */
     final RegExp re = new RegExp(
-        r'^([+-]?\d{4,6})-?(\d\d)-?(\d\d)'  // The day part.
-        r'(?:[ T](\d\d)(?::?(\d\d)(?::?(\d\d)(.\d{1,6})?)?)?' // The time part
-        r'( ?[zZ]| ?([-+])(\d\d)(?::?(\d\d))?)?)?$'); // The timezone part
+        r'^([+-]?\d{4,6})-?(\d\d)-?(\d\d)'  // Day part.
+        r'(?:[ T](\d\d)(?::?(\d\d)(?::?(\d\d)(?:\.(\d{1,6}))?)?)?' // Time part.
+        r'( ?[zZ]| ?([-+])(\d\d)(?::?(\d\d))?)?)?$'); // Timezone part.
 
     Match match = re.firstMatch(formattedString);
     if (match != null) {
       int parseIntOrZero(String matched) {
         if (matched == null) return 0;
         return int.parse(matched);
       }
 
-      double parseDoubleOrZero(String matched) {
-        if (matched == null) return 0.0;
-        return double.parse(matched);
+      // Parses fractional second digits of '.(\d{1,6})' into milliseconds.
+      // Uses first three digits (assumed to be zero if not there), and
+      // rounds up if fourth digit is 5 or greater.
+      // Should be equivalent to `(double.parse(".$matchd")*1000).round()`.
+      int parseMilliseconds(String matched) {
+        if (matched == null) return 0;
+        int length = matched.length;
+        assert(length >= 1);
+        assert(length <= 6);
+
+        int result = (matched.codeUnitAt(0) ^ 0x30);
+        if (length <= 3) {
+          int i = 1;
+          while (i < length) {
+            result *= 10;
+            result += matched.codeUnitAt(i) ^ 0x30;
+            i++;
+          }
+          while (i < 3) {
+            result *= 10;
+            i++;
+          }
+          return result;
+        }
+        // Parse the prefix from 0..3 without creating a new substring.
+        result = result * 10 + (matched.codeUnitAt(1) ^ 0x30);
+        result = result * 10 + (matched.codeUnitAt(2) ^ 0x30);
+        if (matched.codeUnitAt(3) >= 0x35) {
+          result += 1;
+        }
+        return result;
       }
 
       int years = int.parse(match[1]);
       int month = int.parse(match[2]);
       int day = int.parse(match[3]);
       int hour = parseIntOrZero(match[4]);
       int minute = parseIntOrZero(match[5]);
       int second = parseIntOrZero(match[6]);
       bool addOneMillisecond = false;
-      int millisecond = (parseDoubleOrZero(match[7]) * 1000).round();
+      int millisecond = parseMilliseconds(match[7]);
       if (millisecond == 1000) {
         addOneMillisecond = true;
         millisecond = 999;
       }
       bool isUtc = false;
       if (match[8] != null) {  // timezone part
         isUtc = true;
         if (match[9] != null) {
           // timezone other than 'Z' and 'z'.
           int sign = (match[9] == '-') ? -1 : 1;
@@ skipping 372 matching lines @@
    * In accordance with ISO 8601
    * a week starts with Monday, which has the value 1.
    *
    *     DateTime moonLanding = DateTime.parse("1969-07-20 20:18:00");
    *     assert(moonLanding.weekday == 7);
    *     assert(moonLanding.weekday == DateTime.SUNDAY);
    *
    */
   external int get weekday;
 }