[Fb-contrib-commit] fb-contrib/src/com/mebigfatguy/fbcontrib/detect PossibleMemoryBloat.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-serv24111/src/com/mebigfatguy/fbcontrib/detect

Added Files:
	PossibleMemoryBloat.java 
Log Message:
initial checkin - new PMB detector

--- NEW FILE: PossibleMemoryBloat.java ---
package com.mebigfatguy.fbcontrib.detect;

import java.util.HashSet;
import java.util.Set;

import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.FieldAnnotation;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.ba.ClassContext;

/**
 * looks for classes that maintain collections or StringBuffer/StringBuilders in static member
 * variables, and that do not appear to provide a way to clear or remove items from this members.
 * Such member variables are likely causes of memory bloat.
 *
 */
public class PossibleMemoryBloat extends BytecodeScanningDetector implements StatelessDetector {
	private static final Set<String> bloatableSigs = new HashSet<String>();
	static {
		bloatableSigs.add("Ljava/util/ArrayList;");
		bloatableSigs.add("Ljava/util/Collection;");
		bloatableSigs.add("Ljava/util/HashMap;");
		bloatableSigs.add("Ljava/util/HashSet;");
		bloatableSigs.add("Ljava/util/Hashtable;");
		bloatableSigs.add("Ljava/util/IdentityHashMap;");
		bloatableSigs.add("Ljava/util/LinkedHashMap;");
		bloatableSigs.add("Ljava/util/LinkedList;");
		bloatableSigs.add("Ljava/util/List;");
		bloatableSigs.add("Ljava/util/Map;");
		bloatableSigs.add("Ljava/util/Set;");
		bloatableSigs.add("Ljava/util/SortedSet;");
		bloatableSigs.add("Ljava/util/SortedMap;");
		bloatableSigs.add("Ljava/util/Stack;");
		bloatableSigs.add("Ljava/lang/StringBuffer;");
		bloatableSigs.add("Ljava/lang/StringBuilder;");
		bloatableSigs.add("Ljava/util/TreeMap;");
		bloatableSigs.add("Ljava/util/TreeSet;");
		bloatableSigs.add("Ljava/util/Vector;");
	}
	private static final Set<String> clearingMethods = new HashSet<String>();
	static {
		clearingMethods.add("clear");
		clearingMethods.add("delete");
		clearingMethods.add("deleteCharAt");
		clearingMethods.add("pop");
		clearingMethods.add("remove");
		clearingMethods.add("setLength");
	}
	private BugReporter bugReporter;
	private Set<FieldAnnotation> bloatableFields = new HashSet<FieldAnnotation>();
	private OpcodeStack stack = new OpcodeStack();
	
	/**
     * constructs a PMB detector given the reporter to report bugs on
     * @param bugReporter the sync of bug reports
	 */
	public PossibleMemoryBloat(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();
	}
	
	/**
	 * collects static fields that are likely bloatable objects and if found
	 * allows the visitor to proceed, at the end report all leftover fields
	 * 
	 * @param obj the class context object of the currently parsed java class
	 */
	@Override
	public void visitClassContext(ClassContext classContext) {
		bloatableFields.clear();
		JavaClass cls = classContext.getJavaClass();
		Field[] fields = cls.getFields();
		for (Field f : fields) {
			if (f.isStatic()) {
				String sig = f.getSignature();
				if (bloatableSigs.contains(sig)) {
					bloatableFields.add(FieldAnnotation.fromBCELField(cls.getClassName(), f));
				}
			}
		}
		
		if (bloatableFields.size() > 0) {
			super.visitClassContext(classContext);

			for (FieldAnnotation fa : bloatableFields) {
				bugReporter.reportBug(new BugInstance(this, "PMB_POSSIBLE_MEMORY_BLOAT", NORMAL_PRIORITY)
							.addClass(this)
							.addField(fa));
			}
		}
	}
	
	/**
	 * implements the visitor to reset the opcode stack
	 * 
	 * @param obj the context object of the currently parsed code block
	 */
	@Override
	public void visitCode(Code obj) {
		stack.resetForMethodEntry(this);
		if (bloatableFields.size() > 0)
			super.visitCode(obj);
	}
	
	/**
	 * implements the visitor to look for methods that empty a bloatable field
	 * if found, remove these fields from the current list
	 * 
	 * @param obj the context object of the currently parsed instruction
	 */
	@Override
	public void sawOpcode(int seen) {
		try {
			stack.mergeJumps(this);
			
			if (bloatableFields.size() == 0)
				return;
			
			if ((seen == INVOKEVIRTUAL)
			||  (seen == INVOKEINTERFACE)) {
				String sig = getSigConstantOperand();
				int argCount = Type.getArgumentTypes(sig).length;
				if (stack.getStackDepth() > argCount) {
					OpcodeStack.Item itm = stack.getStackItem(argCount);
					FieldAnnotation fa = itm.getField();
					if (fa != null) {
						if (bloatableFields.contains(fa)) {
							String methodName = getNameConstantOperand();
							if (clearingMethods.contains(methodName)) {
								bloatableFields.remove(fa);
							}
						}
					}
				}
			}
		}
		finally {
			stack.sawOpcode(this, seen);
		}
	}
}