[Fb-contrib-commit] fb-contrib/src/com/mebigfatguy/fbcontrib/detect LocalSynchronizedCollection.java,NONE,1.1

[Dave B. <dbr...@us...>]

Update of /cvsroot/fb-contrib/fb-contrib/src/com/mebigfatguy/fbcontrib/detect
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv9538/src/com/mebigfatguy/fbcontrib/detect

Added Files:
	LocalSynchronizedCollection.java 
Log Message:
intial checkin - new LSYC detector

--- NEW FILE: LocalSynchronizedCollection.java ---
/*
 * fb-contrib - Auxilliary detectors for Java programs
 * Copyright (C) 2005-2006 Dave Brosius
 * 
 * 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 com.mebigfatguy.fbcontrib.detect;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.apache.bcel.classfile.Code;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.SourceLineAnnotation;
import edu.umd.cs.findbugs.StatelessDetector;

/**
 * looks for allocations of synchronized collections that are stored in local variables, and 
 * never stored in fields or returned from methods. As local variables are by definition
 * thread safe, using synchronized collections in this context makes no sense.
 */
public class LocalSynchronizedCollection extends BytecodeScanningDetector implements StatelessDetector {
	private static Set<String> syncCtors = new HashSet<String>();
	static {
		syncCtors.add("java/util/Vector");
		syncCtors.add("java/util/Hashtable");
	}
	private static Set<String> syncMethods = new HashSet<String>();
	static {
		syncMethods.add("synchronizedCollection");
		syncMethods.add("synchronizedList");
		syncMethods.add("synchronizedMap");
		syncMethods.add("synchronizedSet");
		syncMethods.add("synchronizedSortedMap");
		syncMethods.add("synchronizedSortedSet");
	}
	
	private BugReporter bugReporter;
	private OpcodeStack stack = new OpcodeStack();
	private Map<Integer, SourceLineAnnotation> syncRegs = new HashMap<Integer, SourceLineAnnotation>();
	
	/**
     * constructs a LSYC detector given the reporter to report bugs on
     * @param bugReporter the sync of bug reports
	 */
	public LocalSynchronizedCollection(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}
	
	/**
	 * clone this detector so that it can be a StatelessDetector
	 * 
	 * @return a clone of this object
	 */
	@Override
	public Object clone() throws CloneNotSupportedException {
		return super.clone();
	}	
	
	/**
	 * implements the visitor to reset the stack
	 * 
	 * @param obj the context object of the currently parsed code block
	 */
	@Override
	public void visitCode(Code obj) {
		stack.resetForMethodEntry(this);
		syncRegs.clear();
		super.visitCode(obj);
		
		for (Map.Entry<Integer, SourceLineAnnotation> entry : syncRegs.entrySet()) {
			bugReporter.reportBug(new BugInstance(this, "LSYC_LOCAL_SYNCHRONIZED_COLLECTION", NORMAL_PRIORITY)
						.addClass(this)
						.addMethod(this)
						.addSourceLine(entry.getValue()));
				
		}
	}
	
	/**
	 * implements the visitor to find stores to locals of synchronized collections
	 * 
	 * @param seen the opcode of the currently parsed instruction
	 */
	@Override
	public void sawOpcode(int seen) {
		Integer tosIsSyncColReg = null;
		try {
			stack.mergeJumps(this);
			
			if (seen == INVOKESPECIAL) {
				if ("<init>".equals(getNameConstantOperand())) {
					if (syncCtors.contains(getClassConstantOperand())) {
						tosIsSyncColReg = new Integer(-1);
					}
				}
			} else if (seen == INVOKESTATIC) {
				if ("java/util/Collections".equals(getClassConstantOperand())) {
					if (syncMethods.contains(getNameConstantOperand())) {
						tosIsSyncColReg = new Integer(-1);
					}
				}
			} else if ((seen == ASTORE) || ((seen >= ASTORE_0) && (seen <= ASTORE_3))) {
				if (stack.getStackDepth() > 0) {
					OpcodeStack.Item item = stack.getStackItem(0);
					if (item.getUserValue() != null) {
						int reg = getAStoreReg(seen);
						if (!syncRegs.containsKey(reg))
							syncRegs.put(new Integer(reg), SourceLineAnnotation.fromVisitedInstruction(this));
					}
				}
			} else if ((seen == ALOAD) || ((seen >= ALOAD_0) && (seen <= ALOAD_3))) {
				int reg = getALoadReg(seen);
				if (syncRegs.containsKey(new Integer(reg)))
					tosIsSyncColReg = new Integer(reg);
			} else if ((seen == PUTFIELD) || (seen == ARETURN)) {
				if (stack.getStackDepth() > 0) {
					OpcodeStack.Item item = stack.getStackItem(0);
					syncRegs.remove(item.getUserValue());
				}				
			}			
		} finally {
			stack.sawOpcode(this, seen);
			if (tosIsSyncColReg != null) {
				if (stack.getStackDepth() > 0) {
					OpcodeStack.Item item = stack.getStackItem(0);
					item.setUserValue(tosIsSyncColReg);
				}
			}
		}
	}

	/**
	 * returns the register used to store a reference
	 * 
	 * @param seen the opcode of the store
	 * @return the register stored into
	 */
	private int getAStoreReg(int seen) {
		if (seen == ASTORE)
			return getRegisterOperand();
		return seen - ASTORE_0;
	}
	
	/**
	 * returns the register used to load a reference
	 * 
	 * @param seen the opcode of the load
	 * @return the register loaded from
	 */	
	private int getALoadReg(int seen) {
		if (seen == ALOAD)
			return getRegisterOperand();
		return seen - ALOAD_0;
	}	
}