Speed up ASCII, LATIN1, UTF8 converters, for single-byte codeunits.

sdk/lib/convert/latin1.dart

 // Copyright (c) 2013, 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.convert;
 
 /**
  * An instance of the default implementation of the [Latin1Codec].
  *
  * This instance provides a convenient access to the most common ISO Latin 1
@@ skipping 107 matching lines @@
     _sink.close();
   }
 
   void add(List<int> source) {
     addSlice(source, 0, source.length, false);
   }
 
   void _addSliceToSink(List<int> source, int start, int end, bool isLast) {
     // If _sink was a UTF-16 conversion sink, just add the slice directly with
     // _sink.addSlice(source, start, end, isLast).
-    // The code below is an incredibly stupid workaround until a real
+    // The code below is an moderately stupid workaround until a real
     // solution can be made.
-    _sink.add(new String.fromCharCodes(source.getRange(start, end)));
+    if (start == 0 && end == source.length) {
+      _sink.add(new String.fromCharCodes(source));
+    } else {
+      _sink.add(new String.fromCharCodes(source.sublist(start, end)));
+    }
     if (isLast) close();
   }
 
   void addSlice(List<int> source, int start, int end, bool isLast) {
+    // If Uint8List, just add dircetly.
+    if (source is Uint8List) {
+      _addSliceToSink(source, start, end, isLast);
+      return;
+    }
     if (start < 0 || start > source.length) {
       throw new RangeError.range(start, 0, source.length);
     }
     if (end < start || end > source.length) {
       throw new RangeError.range(end, start, source.length);
     }
     for (int i = start; i < end; i++) {
       if ((source[i] & ~_LATIN1_MASK) != 0) {
         if (_allowInvalid) {
           if (i > start) _addSliceToSink(source, start, i, false);
           // Add UTF-8 encoding of U+FFFD.
           _addSliceToSink(const[0xFFFD], 0, 1, false);
           start = i + 1;
         } else {
           throw new FormatException("Source contains non-Latin-1 characters.");
         }
       }
     }
     if (start < end) {
       _addSliceToSink(source, start, end, isLast);
     } else if (isLast) {
       close();
     }
   }
 }