# SystemPropertiesRuntime.java

    /*******************************************************************************
     * Copyright (c) 2009, 2013 Mountainminds GmbH & Co. KG and Contributors
     * All rights reserved. This program and the accompanying materials
     * are made available under the terms of the Eclipse Public License v1.0
     * which accompanies this distribution, and is available at
     * http://www.eclipse.org/legal/epl-v10.html
     *
     * Contributors:
     *    Marc R. Hoffmann - initial API and implementation
     *
     *******************************************************************************/
    package org.jacoco.core.runtime;

    import org.objectweb.asm.MethodVisitor;
    import org.objectweb.asm.Opcodes;

    /**
     * This {@link IRuntime} implementation makes the execution data available
     * through a special entry in the {@link System#getProperties()} hash table. The
     * advantage is, that the instrumented classes do not get dependencies to other
     * classes than the JRE library itself.
     *
     * This runtime may cause problems in environments with security restrictions,
     * in applications that replace the system properties or in applications that
     * fail if non-String values are placed in the system properties.
     */
    public class SystemPropertiesRuntime extends AbstractRuntime {

    	private static final String KEYPREFIX = "jacoco-";

    	private final String key;

    	/**
    	 * Creates a new runtime.
    	 */
    	public SystemPropertiesRuntime() {
    		super();
    		this.key = KEYPREFIX + Integer.toHexString(hashCode());
    	}

    	public int generateDataAccessor(final long classid, final String classname,
    			final int probecount, final MethodVisitor mv) {
    		mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/System",
    				"getProperties", "()Ljava/util/Properties;");

    		// Stack[0]: Ljava/util/Properties;

    		mv.visitLdcInsn(key);

    		// Stack[1]: Ljava/lang/String;
    		// Stack[0]: Ljava/util/Properties;

    		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/util/Properties",
    				"get", "(Ljava/lang/Object;)Ljava/lang/Object;");

    		// Stack[0]: Ljava/lang/Object;

    		RuntimeData.generateAccessCall(classid, classname, probecount, mv);

    		// Stack[0]: [Z

    		return 6; // Maximum local stack size is 3
    	}

    	@Override
    	public void startup(final RuntimeData data) throws Exception {
    		super.startup(data);
    		System.getProperties().put(key, data);
    	}

    	public void shutdown() {
    		System.getProperties().remove(key);
    	}

    }