Optimize latin1-decoder.

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 87 matching lines @@
    * [StringConversionSink].
    */
   ByteConversionSink startChunkedConversion(Sink<String> sink) {
     StringConversionSink stringSink;
     if (sink is StringConversionSink) {
       stringSink = sink;
     } else {
       stringSink = new StringConversionSink.from(sink);
     }
     // TODO(lrn): Use stringSink.asUtf16Sink() if it becomes available.
-    return new _Latin1DecoderSink(_allowInvalid, stringSink);
+    if (!_allowInvalid) return new _Latin1DecoderSink(stringSink);
+    return new _Latin1AllowInvalidDecoderSink(stringSink);
   }
 }
 
 class _Latin1DecoderSink extends ByteConversionSinkBase {
-  final bool _allowInvalid;
   StringConversionSink _sink;
-  _Latin1DecoderSink(this._allowInvalid, this._sink);
+  _Latin1DecoderSink(this._sink);
 
   void close() {
     _sink.close();
   }
 
   void add(List<int> source) {
     addSlice(source, 0, source.length, false);
   }
 
   void _addSliceToSink(List<int> source, int start, int end, bool isLast) {
@@ skipping 10 matching lines @@
   }
 
   void addSlice(List<int> source, int start, int end, bool isLast) {
     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.");
-        }
+      int char = source[i];
+      if (char < 0 || char > _LATIN1_MASK) {

[Lasse Reichstein Nielsen, 2014/08/08 07:29:01]

This test seems to be ~10% faster than the "&" test *if it is almost always
true*, which is the expected case here.

+        throw new FormatException("Source contains non-Latin-1 characters.");
       }
     }
     if (start < end) {
+      _addSliceToSink(source, start, end, isLast);
+    }
+    if (isLast) {
+      close();
+    }
+  }
+}
+
+class _Latin1AllowInvalidDecoderSink extends _Latin1DecoderSink {
+  _Latin1AllowInvalidDecoderSink(StringSink sink): super(sink);
+
+  void addSlice(List<int> source, int start, int end, bool isLast) {
+    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++) {
+      int char = source[i];
+      if (char < 0 || char > _LATIN1_MASK) {
+        if (i > start) _addSliceToSink(source, start, i, false);
+        // Add UTF-8 encoding of U+FFFD.
+        _addSliceToSink(const[0xFFFD], 0, 1, false);
+        start = i + 1;
+      }
+    }
+    if (start < end) {
       _addSliceToSink(source, start, end, isLast);
     }
     if (isLast) {
       close();
     }
   }
 }