# URLStreamHandlerRuntime.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 java.io.IOException;
    import java.lang.reflect.Field;
    import java.net.URL;
    import java.net.URLConnection;
    import java.net.URLStreamHandler;
    import java.util.Map;

    import org.jacoco.core.internal.instr.InstrSupport;
    import org.objectweb.asm.MethodVisitor;
    import org.objectweb.asm.Opcodes;

    /**
     * This {@link IRuntime} implementation registers a special
     * {@link URLStreamHandler} to process coverage data. The handler is not
     * actually used for opening a URL, but to get access to the runtime object.
     */
    public class URLStreamHandlerRuntime extends AbstractRuntime {

    	private static final String PROTOCOLPREFIX = "jacoco-";

    	private final String protocol;

    	private Map<String, URLStreamHandler> handlers;

    	/**
    	 * Creates a new runtime.
    	 */
    	public URLStreamHandlerRuntime() {
    		super();
    		protocol = PROTOCOLPREFIX + Integer.toHexString(hashCode());
    	}

    	@Override
    	public void startup(final RuntimeData data) throws Exception {
    		super.startup(data);
    		handlers = getHandlersReference();
    		handlers.put(protocol, handler);
    	}

    	private Map<String, URLStreamHandler> getHandlersReference()
    			throws Exception {
    		final Field field = URL.class.getDeclaredField("handlers");
    		field.setAccessible(true);
    		@SuppressWarnings("unchecked")
    		final Map<String, URLStreamHandler> map = (Map<String, URLStreamHandler>) field
    				.get(null);
    		return map;
    	}

    	public void shutdown() {
    		handlers.remove(protocol);
    	}

    	public int generateDataAccessor(final long classid, final String classname,
    			final int probecount, final MethodVisitor mv) {

    		// The data accessor performs the following steps:
    		//
    		// final URL url = new URL(protocol, null, "");
    		// final URLConnection connection = url.openConnection();
    		// final Object[] args = new Object[3];
    		// args[0] = Long.valueOf(classid);
    		// args[1] = classname;
    		// args[2] = Integer.valueOf(probecount);
    		// connection.equals(args);
    		// final byte[] probedata = (byte[]) args[0];

    		RuntimeData.generateArgumentArray(classid, classname, probecount, mv);
    		mv.visitInsn(Opcodes.DUP);

    		// Stack[1]: [Ljava/lang/Object;
    		// Stack[0]: [Ljava/lang/Object;

    		mv.visitTypeInsn(Opcodes.NEW, "java/net/URL");
    		mv.visitInsn(Opcodes.DUP);
    		mv.visitLdcInsn(protocol);
    		mv.visitInsn(Opcodes.ACONST_NULL);
    		mv.visitLdcInsn("");
    		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/net/URL", "<init>",
    				"(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)V");

    		// Stack[2]: [Ljava/net/URL;
    		// Stack[1]: [Ljava/lang/Object;
    		// Stack[0]: [Ljava/lang/Object;

    		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/net/URL",
    				"openConnection", "()Ljava/net/URLConnection;");

    		// Stack[2]: [Ljava/net/URLConnection;
    		// Stack[1]: [Ljava/lang/Object;
    		// Stack[0]: [Ljava/lang/Object;

    		mv.visitInsn(Opcodes.SWAP);

    		// Stack[2]: [Ljava/lang/Object;
    		// Stack[1]: [Ljava/net/URLConnection;
    		// Stack[0]: [Ljava/lang/Object;

    		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Object", "equals",
    				"(Ljava/lang/Object;)Z");

    		// Stack[1]: Z;
    		// Stack[0]: [Ljava/lang/Object;

    		mv.visitInsn(Opcodes.POP);

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

    		mv.visitInsn(Opcodes.ICONST_0);
    		mv.visitInsn(Opcodes.AALOAD);
    		mv.visitTypeInsn(Opcodes.CHECKCAST, InstrSupport.DATAFIELD_DESC);

    		return 7;
    	}

    	private final URLStreamHandler handler = new URLStreamHandler() {
    		@Override
    		protected URLConnection openConnection(final URL u) throws IOException {
    			return connection;
    		}
    	};

    	private final URLConnection connection = new URLConnection(null) {
    		@Override
    		public void connect() throws IOException {
    			throw new AssertionError();
    		}

    		@Override
    		public boolean equals(final Object obj) {
    			return data.equals(obj);
    		}
    	};

    }