/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2003-2008 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.ba;

import org.apache.bcel.classfile.Attribute;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;

import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;

/**
 * @author pwilliam
 */
public class OpcodeStackScanner {

	static class EarlyExitException extends RuntimeException {
		final OpcodeStack stack;

		public EarlyExitException(OpcodeStack stack) {

			this.stack = stack;
		}
	}

	public static OpcodeStack getStackAt(JavaClass theClass, Method method, int pc) {
		Scanner scanner = new Scanner(theClass, method, pc);
		try {
			scanner.execute();
		} catch (EarlyExitException e) {
			return e.stack;
		}
		throw new IllegalArgumentException("Didn't reach pc " + pc + " of " + method);
	}

	static class Scanner extends OpcodeStackDetector {

		Scanner(JavaClass theClass, Method targetMethod, int targetPC) {
			this.theClass = theClass;
			this.targetMethod = targetMethod;
			this.targetPC = targetPC;
		}

		final JavaClass theClass;

		final Method targetMethod;

		final int targetPC;

		@Override
		public void sawOpcode(int seen) {
			if (getPC() == targetPC)
				throw new EarlyExitException(stack);
		}

		@Override
		public void visitJavaClass(JavaClass obj) {
			setupVisitorForClass(obj);
			getConstantPool().accept(this);
			doVisitMethod(targetMethod);
		}

		public void execute() {
			theClass.accept(this);
		}
	}

}