Improve performance of string buffer by modifying concatAll native to allow growable array and an i…

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);
   }
 }
 
@@ skipping 377 matching lines @@
     }
     buffer.write(onNonMatch(this.substring(startIndex)));
     return buffer.toString();
   }
 
 
   /**
    * Convert all objects in [values] to strings and concat them
    * into a result string.
    */
-  static String _interpolate(List values) {
+  static String _interpolate(List<String> values) {
     final int numValues = values.length;
-    _ObjectArray stringList = new List(numValues);
+    _ObjectArray stringList = new List<String>(numValues);
     bool isOneByteString = true;
     int totalLength = 0;
     for (int i = 0; i < numValues; i++) {
       var s = values[i].toString();
       if (isOneByteString && (s._cid == _OneByteString._classId)) {
         totalLength += s.length;
       } else {
         isOneByteString = false;
       }
       stringList[i] = s;
     }
     if (isOneByteString) {
       return _OneByteString._concatAll(stringList, totalLength);
     }
-    return _concatAllNative(stringList);
+    return _concatAllNative(stringList, 0, stringList.length);
   }
 
   Iterable<Match> allMatches(String str) {
     List<Match> result = new List<Match>();
     int length = str.length;
     int patternLength = this.length;
     int startIndex = 0;
     while (true) {
       int position = str.indexOf(this, startIndex);
       if (position == -1) {
@@ skipping 64 matching lines @@
   }
 
   List<int> get codeUnits => new _CodeUnits(this);
 
   Runes get runes => new Runes(this);
 
   String toUpperCase() native "String_toUpperCase";
 
   String toLowerCase() native "String_toLowerCase";
 
-  // Call this method if not all list elements are OneByteString-s.
-  static String _concatAllNative(_ObjectArray<String> strings)
+  // Call this method if not all list elements are known to be OneByteString(s).
+  // 'strings' must be an _ObjectArray or _GrowableObjectArray.
+  static String _concatAllNative(List<String> strings, int start, int end)
       native "Strings_concatAll";
 }
 
 
 class _OneByteString extends _StringBase implements String {
   static final int _classId = "A"._cid;
 
   factory _OneByteString._uninstantiable() {
     throw new UnsupportedError(
         "_OneByteString can only be allocated by the VM");
@@ skipping 16 matching lines @@
       return _splitWithCharCode(pattern.codeUnitAt(0));
     }
     return super.split(pattern);
   }
 
   // All element of 'strings' must be OneByteStrings.
   static _concatAll(_ObjectArray<String> strings, int totalLength) {
     // TODO(srdjan): Improve code below and raise or eliminate the limit.
     if (totalLength > 128) {
       // Native is quicker.
-      return _StringBase._concatAllNative(strings);
+      return _StringBase._concatAllNative(strings, 0, strings.length);
     }
     var res = _OneByteString._allocate(totalLength);
     final stringsLength = strings.length;
     int rIx = 0;
     for (int i = 0; i < stringsLength; i++) {
       _OneByteString e = strings[i];
       final eLength = e.length;
       for (int s = 0; s < eLength; s++) {
         res._setAt(rIx++, e.codeUnitAt(s));
       }
@@ skipping 85 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);
 }