SyntaxTreeOptimizer.java revision 56ed4167b942ec265f9cee70ac4d71d10b3835ce 
1/*
2 * Copyright (C) 2010 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.clearsilver.jsilver.syntax;
18
19import com.google.clearsilver.jsilver.syntax.analysis.DepthFirstAdapter;
20import com.google.clearsilver.jsilver.syntax.node.AMultipleCommand;
21import com.google.clearsilver.jsilver.syntax.node.AOptimizedMultipleCommand;
22
23/**
24 * Visitor that can be applied to the AST to optimize it by replacing nodes with more efficient
25 * implementations than the default SableCC generated versions.
26 */
27public class SyntaxTreeOptimizer extends DepthFirstAdapter {
28
29  /**
30   * Replace AMultipleCommand nodes with AOptimizedMultipleCommands, which iterates over children
31   * faster.
32   */
33  @Override
34  public void caseAMultipleCommand(AMultipleCommand originalNode) {
35    // Recurse through child nodes first. Because the optimised node doesn't
36    // handle replacement, go leaves-first.
37    super.caseAMultipleCommand(originalNode);
38    // Replace this node with the optimized version.
39    originalNode.replaceBy(new AOptimizedMultipleCommand(originalNode));
40  }
41
42}
43