hugesharedstringconstants.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004-2006 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 java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantString;
import org.apache.bcel.classfile.ConstantValue;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.IntAnnotation;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;

public class HugeSharedStringConstants extends BytecodeScanningDetector {

	/**
	 * 
	 */
	private static final int SIZE_OF_HUGE_CONSTANT = 500;

	String getStringKey(String s) {
		return s.length() + ":" + s.hashCode();
	}

	HashMap<String, SortedSet<String>> map = new HashMap<String, SortedSet<String>>();

	HashMap<String, XField> definition = new HashMap<String, XField>();

	HashMap<String, Integer> stringSize = new HashMap<String, Integer>();

	BugReporter bugReporter;

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

	@Override
	public void visit(ConstantString s) {
		String value = s.getBytes(getConstantPool());
		if (value.length() < SIZE_OF_HUGE_CONSTANT)
			return;
		String key = getStringKey(value);
		SortedSet<String> set = map.get(key);
		if (set == null) {
			set = new TreeSet<String>();
			map.put(key, set);
		}
		set.add(getDottedClassName());
	}

	@Override
	public void visit(ConstantValue s) {
		if (!visitingField())
			return;
		int i = s.getConstantValueIndex();
		Constant c = getConstantPool().getConstant(i);
		if (c instanceof ConstantString) {
			String value = ((ConstantString) c).getBytes(getConstantPool());
			if (value.length() < SIZE_OF_HUGE_CONSTANT)
				return;
			String key = getStringKey(value);
			definition.put(key, XFactory.createXField(this));
			stringSize.put(key, value.length());
		}

	}

	@Override
	public void report() {
		for (Map.Entry<String, SortedSet<String>> e : map.entrySet()) {
			Set<String> occursIn = e.getValue();
			if (occursIn.size() == 1)
				continue;
			XField field = definition.get(e.getKey());
			if (field == null) continue;
			Integer length = stringSize.get(e.getKey());
			int overhead = length * (occursIn.size()-1);
			if (overhead < 3*SIZE_OF_HUGE_CONSTANT) continue;
			String className = field.getClassName();

			BugInstance bug = new BugInstance(this, "HSC_HUGE_SHARED_STRING_CONSTANT",
					overhead > 20*SIZE_OF_HUGE_CONSTANT ? HIGH_PRIORITY : 
						( overhead > 8*SIPUSH ? NORMAL_PRIORITY : LOW_PRIORITY))
						.addClass(className).addField(field).addInt(length).addInt(occursIn.size()).describe(IntAnnotation.INT_OCCURRENCES);
			for (String c : occursIn)
				if (!c.equals(className))
					bug.addClass(c);

			bugReporter.reportBug(bug);

		}

	}

}