Monitorenter


1   /*
2    * Bytecode Analysis Framework
3    * Copyright (C) 2003,2004 University of Maryland
4    * 
5    * This library is free software; you can redistribute it and/or
6    * modify it under the terms of the GNU Lesser General Public
7    * License as published by the Free Software Foundation; either
8    * version 2.1 of the License, or (at your option) any later version.
9    * 
10   * This library is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   * Lesser General Public License for more details.
14   * 
15   * You should have received a copy of the GNU Lesser General Public
16   * License along with this library; if not, write to the Free Software
17   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18   */
19  
20  package edu.umd.cs.findbugs.ba.bcp;
21  
22  import org.apache.bcel.generic.ConstantPoolGen;
23  import org.apache.bcel.generic.Instruction;
24  import org.apache.bcel.generic.InstructionHandle;
25  import org.apache.bcel.generic.MONITORENTER;
26  
27  import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
28  import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
29  
30  /**
31   * A PatternElement for matching a MONITORENTER instruction.
32   *
33   * @author DavidHovemeyer
34   */
35  public class Monitorenter extends OneVariableInstruction {
36      /**
37       * Constructor.
38       *
39       * @param varName name of the variable representing the reference
40       *                to the object being locked
41       */
42      public Monitorenter(String   varName) {
43          super(varName);
44      }
45  
46      @Override  
47           public MatchResult match(InstructionHandle handle, ConstantPoolGen cpg,
48                               ValueNumberFrame before, ValueNumberFrame after, BindingSet bindingSet) throws DataflowAnalysisException {
49  
50          // Instruction must be MONITORENTER.
51          Instruction ins = handle.getInstruction();
52          if (!(ins instanceof MONITORENTER))
53              return null;
54  
55          // Ensure the object being locked matches any previous
56          // instructions which bound our variable name to a value.
57          Variable lock = new LocalVariable(before.getTopValue());
58          return addOrCheckDefinition(lock, bindingSet);
59      }
60  }
61  
62  // vim:ts=4
63
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