Optimize int.parse with a radix.

runtime/lib/string_patch.dart

 // Copyright (c) 2012, 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.
 
 patch class String {
   /* patch */ factory String.fromCharCodes(Iterable<int> charCodes) {
     return _StringBase.createFromCharCodes(charCodes);
   }
 
   /* patch */ factory String.fromCharCode(int charCode) {
@@ skipping 242 matching lines @@
     if ((startIndex + 1) == endIndex) {
       return this[startIndex];
     }
     return _substringUncheckedNative(startIndex, endIndex);
   }
 
   String _substringUncheckedNative(int startIndex, int endIndex)
       native "StringBase_substringUnchecked";
 
   // Checks for one-byte whitespaces only.
-  static bool _isOneByteWhitespace(int codePoint) {
-    return
-      (codePoint == 32) || // Space.
-      ((codePoint <= 13) ? (9 <= codePoint)  // CR, LF, TAB, etc.
-                         : ((codePoint == 0x85) ||  // NEL
-                            (codePoint == 0xA0)));  // NBSP
+  static bool _isOneByteWhitespace(int codeUnit) {
+    if (codeUnit <= 32) {
+      return ((codeUnit == 32) || // Space.
+              ((codeUnit <= 13) && (codeUnit >= 9)));  // CR, LF, TAB, etc.
+    }
+    if (codeUnit < 0x85) return false;

[srdjan, 2014/09/24 20:05:35]

Is that check worth it? With two below you have three checks instead of two and
more complex code.

[Lasse Reichstein Nielsen, 2014/09/24 20:26:30]

Ack, probably not for the one-byte case. I copied it from the two-byte case
where it's guarding a much more complex test.

[Lasse Reichstein Nielsen, 2014/09/25 14:37:16]

Fixed.
Any chance of optimizing so that (codeunit < 0x85) followed by (codeunit ==
0x85) always boils down to one compare instruction? :)

+    return (codeUnit == 0x85) || (codeUnit == 0xA0);
   }
 
   // Characters with Whitespace property (Unicode 6.2).
   // 0009..000D    ; White_Space # Cc       <control-0009>..<control-000D>
   // 0020          ; White_Space # Zs       SPACE
   // 0085          ; White_Space # Cc       <control-0085>
   // 00A0          ; White_Space # Zs       NO-BREAK SPACE
   // 1680          ; White_Space # Zs       OGHAM SPACE MARK
   // 180E          ; White_Space # Zs       MONGOLIAN VOWEL SEPARATOR
   // 2000..200A    ; White_Space # Zs       EN QUAD..HAIR SPACE
   // 2028          ; White_Space # Zl       LINE SEPARATOR
   // 2029          ; White_Space # Zp       PARAGRAPH SEPARATOR
   // 202F          ; White_Space # Zs       NARROW NO-BREAK SPACE
   // 205F          ; White_Space # Zs       MEDIUM MATHEMATICAL SPACE
   // 3000          ; White_Space # Zs       IDEOGRAPHIC SPACE
   //
   // BOM: 0xFEFF
   static bool _isTwoByteWhitespace(int codeUnit) {
-    if (codeUnit <= 0xA0) return _isOneByteWhitespace(codeUnit);
+    if (codeUnit <= 32) {
+      return (codeUnit == 32) ||
+             ((codeUnit <= 13) && (codeUnit >= 9));
+    }
+    if (codeUnit < 0x85) return false;
+    if ((codeUnit == 0x85) || (codeUnit == 0xA0)) return true;
     return (codeUnit <= 0x200A)
             ? ((codeUnit == 0x1680) ||
                (codeUnit == 0x180E) ||
                (0x2000 <= codeUnit))
             : ((codeUnit == 0x2028) ||
                (codeUnit == 0x2029) ||
                (codeUnit == 0x202F) ||
                (codeUnit == 0x205F) ||
                (codeUnit == 0x3000) ||
                (codeUnit == 0xFEFF));
@@ skipping 720 matching lines @@
 class _CodeUnits extends Object with ListMixin<int>,
                                      UnmodifiableListMixin<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }