wrongmapiterator.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004,2005 Dave Brosius <[e-mail]>
 * Copyright (C) 2004,2005 University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.detect;


import edu.umd.cs.findbugs.*;
import org.apache.bcel.classfile.Method;

public class WrongMapIterator extends BytecodeScanningDetector implements   StatelessDetector {
	private BugReporter bugReporter;
	private static final int SAW_NOTHING = 0;
	private static final int SAW_MAP_LOAD1 = 1;
	private static final int SAW_KEYSET = 2;
	private static final int SAW_KEYSET_STORE = 3;    
	private static final int SAW_ITERATOR = 4;
	private static final int SAW_ITERATOR_STORE = 5;
	private static final int SAW_ITERATOR_LOAD = 6;
	private static final int SAW_NEXT = 7;
	private static final int SAW_CHECKCAST_ON_NEXT = 8;
	private static final int SAW_KEY_STORE = 9;
	private static final int NEED_KEYSET_LOAD = 10;
	private static final int SAW_MAP_LOAD2 = 11;    
	private static final int SAW_KEY_LOAD = 12;

	private int state;
	private int loadedRegister;
	private int mapRegister;
	private int keySetRegister;
	private int iteratorRegister;
	private int keyRegister;


	public WrongMapIterator(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}



	@Override
		 public void visit(Method obj) {
		state = SAW_NOTHING;
		loadedRegister = -1;
		mapRegister = -1;
		keySetRegister = -1;
		iteratorRegister = -1;
		keyRegister = -1;
	}

	@Override
	public void sawOpcode(int seen) {
		switch (state)
		{
			case SAW_NOTHING:
				loadedRegister = getLoadStoreRegister( seen, true );
				if (loadedRegister >= 0)
					state = SAW_MAP_LOAD1;
			break;

			case SAW_MAP_LOAD1:
				if (((seen == INVOKEINTERFACE) || (seen == INVOKEVIRTUAL))
				&&  ("keySet".equals(getNameConstantOperand()))
				&&  ("()Ljava/util/Set;".equals(getSigConstantOperand()))) {
					mapRegister = loadedRegister;
					state = SAW_KEYSET;
				}
				else {
					state = SAW_NOTHING;
				}
			break;

			case SAW_KEYSET:
				keySetRegister = getLoadStoreRegister( seen, false );
				if (keySetRegister >= 0)
					state = SAW_KEYSET_STORE;
				else if ((seen == INVOKEINTERFACE)
				&&  ("iterator".equals(getNameConstantOperand()))
				&&  ("()Ljava/util/Iterator;".equals(getSigConstantOperand())))
					state = SAW_ITERATOR;
				else
					state = SAW_NOTHING;
			break;

			case SAW_KEYSET_STORE:	
				if ((seen == INVOKEINTERFACE)
				&&  ("iterator".equals(getNameConstantOperand()))
				&&  ("()Ljava/util/Iterator;".equals(getSigConstantOperand())))
					state = SAW_ITERATOR;
				else
					state = NEED_KEYSET_LOAD;
			break;

			case NEED_KEYSET_LOAD:
				loadedRegister = getLoadStoreRegister( seen, true );
				if (loadedRegister == iteratorRegister)
					state = SAW_ITERATOR;
			break;

			case SAW_ITERATOR:
				iteratorRegister = getLoadStoreRegister( seen, false );
				if (iteratorRegister >= 0)
					state = SAW_ITERATOR_STORE;
				else
					state = SAW_NOTHING;
			break;

			case SAW_ITERATOR_STORE:
				loadedRegister = getLoadStoreRegister( seen, true );
				if (loadedRegister == iteratorRegister)
					state = SAW_ITERATOR_LOAD;
			break;

			case SAW_ITERATOR_LOAD:
				if ((seen == INVOKEINTERFACE)
				&&  ("next".equals(getNameConstantOperand()))
				&&  ("()Ljava/lang/Object;".equals(getSigConstantOperand())))
					state = SAW_NEXT;
				else
					state = SAW_ITERATOR_STORE;
			break;

			case SAW_NEXT:
				if (seen == CHECKCAST)
					state = SAW_CHECKCAST_ON_NEXT;
				   else {
					   keyRegister = getLoadStoreRegister( seen, false );
					   if (keyRegister >= 0)
						   state = SAW_KEY_STORE;
					   else
						   state = SAW_NOTHING;
				   }
			 break;

			case SAW_CHECKCAST_ON_NEXT:
				keyRegister = getLoadStoreRegister( seen, false );
				if (keyRegister >= 0)
					state = SAW_KEY_STORE;
			break;

			case SAW_KEY_STORE:
				loadedRegister = getLoadStoreRegister( seen, true );
				if (loadedRegister == mapRegister)
					state = SAW_MAP_LOAD2;
			break;

			case SAW_MAP_LOAD2:
				loadedRegister = getLoadStoreRegister( seen, true );
				if (loadedRegister == keyRegister)
					state = SAW_KEY_LOAD;
				else
					state = SAW_KEY_STORE;
			break;

			case SAW_KEY_LOAD:
				if (((seen == INVOKEINTERFACE) || (seen == INVOKEVIRTUAL))
				&&  ("get".equals(getNameConstantOperand()))
				&&  ("(Ljava/lang/Object;)Ljava/lang/Object;".equals(getSigConstantOperand()))) {
					MethodAnnotation ma = MethodAnnotation.fromVisitedMethod(this);
					bugReporter.reportBug(
						new BugInstance("WMI_WRONG_MAP_ITERATOR", NORMAL_PRIORITY)
														.addClass(this)
														.addMethod(ma)
														.addSourceLine(this, getPC()));
					state = SAW_NOTHING;
				}
			break;
		}
	}

	private int getLoadStoreRegister(int seen, boolean doLoad)
	{
		switch (seen)
		{
			case ALOAD_0:
			case ALOAD_1:
			case ALOAD_2:
			case ALOAD_3:
				if (doLoad)
					return seen - ALOAD_0;
			break;

			case ALOAD:
				if (doLoad)
					return getRegisterOperand();
			break;

			case ASTORE_0:
			case ASTORE_1:
			case ASTORE_2:
			case ASTORE_3:
				if (!doLoad)
					return seen - ASTORE_0;
			break;

			case ASTORE:
				if (!doLoad)
					return getRegisterOperand();
			break;
		}

		return -1;
	}
}