ExecutionDataAccess.java

    1/*******************************************************************************
    2 * Copyright (c) 2009, 2010 Mountainminds GmbH & Co. KG and Contributors
    3 * All rights reserved. This program and the accompanying materials
    4 * are made available under the terms of the Eclipse Public License v1.0
    5 * which accompanies this distribution, and is available at
    6 * http://www.eclipse.org/legal/epl-v10.html
    7 *
    8 * Contributors:
    9 *    Marc R. Hoffmann - initial API and implementation
   10 *    
   11 * $Id: $
   12 *******************************************************************************/
   13package org.jacoco.core.runtime;
   14
   15import org.jacoco.core.data.ExecutionDataStore;
   16import org.jacoco.core.instr.InstrSupport;
   17import org.objectweb.asm.MethodVisitor;
   18import org.objectweb.asm.Opcodes;
   19
   20/**
   21 * This class implements the access from instrumented classes to execution data
   22 * storage in the runtime. Instead of directly referencing JaCoCo implementation
   23 * classes the access is decoupled through a JRE API. This avoids dependencies
   24 * from instrumented classes on JaCoCo APIs.
   25 * 
   26 * The JRE interface method used is {@link Object#equals(Object)} where the
   27 * passed argument is an {@link Object} array containing the class id (
   28 * {@link Long}), the class vm name ({@link String}) and the probe count (
   29 * {@link Integer}). After the method call the probe array instance is stored in
   30 * the first slot of the {@link Object} array.
   31 * 
   32 * @author Marc R. Hoffmann
   33 * @version $Revision: $
   34 */
   35class ExecutionDataAccess {
   36
   37    private final ExecutionDataStore store;
   38
   39    ExecutionDataAccess(final ExecutionDataStore store) {
   40        this.store = store;
   41    }
   42
   43    /**
   44     * Retrieves the execution probe array for a given class. The passed
   45     * {@link Object} array instance is used for parameters and the return value
   46     * as follows. Call parameters:
   47     * 
   48     * <ul>
   49     * <li>args[0]: class id ({@link Long})
   50     * <li>args[1]: vm class name ({@link String})
   51     * <li>args[2]: probe count ({@link Integer})
   52     * </ul>
   53     * 
   54     * Return value:
   55     * 
   56     * <ul>
   57     * <li>args[0]: probe array (<code>boolean[]</code>)
   58     * </ul>
   59     * 
   60     * @param args
   61     *            parameter array of length 3
   62     */
   63    public void getExecutionData(final Object[] args) {
   64        final Long classid = (Long) args[0];
   65        final String name = (String) args[1];
   66        final int probecount = ((Integer) args[2]).intValue();
   67        synchronized (store) {
   68            args[0] = store.getData(classid, name, probecount);
   69        }
   70    }
   71
   72    /**
   73     * Generates code that creates the argument array for the
   74     * <code>getExecutionData()</code> method. The array instance is left on the
   75     * operand stack. The generated code requires a stack size of 5.
   76     * 
   77     * @param classid
   78     *            class identifier
   79     * @param classname
   80     *            VM class name
   81     * @param probecount
   82     *            probe count for this class
   83     * @param mv
   84     *            visitor to emit generated code
   85     */
   86    public static void generateArgumentArray(final long classid,
   87            final String classname, final int probecount, final MethodVisitor mv) {
   88        mv.visitInsn(Opcodes.ICONST_3);
   89        mv.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");
   90
   91        // Class Id:
   92        mv.visitInsn(Opcodes.DUP);
   93        mv.visitInsn(Opcodes.ICONST_0);
   94        mv.visitLdcInsn(Long.valueOf(classid));
   95        mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Long", "valueOf",
   96                "(J)Ljava/lang/Long;");
   97        mv.visitInsn(Opcodes.AASTORE);
   98
   99        // Class Name:
  100        mv.visitInsn(Opcodes.DUP);
  101        mv.visitInsn(Opcodes.ICONST_1);
  102        mv.visitLdcInsn(classname);
  103        mv.visitInsn(Opcodes.AASTORE);
  104
  105        // Probe Count:
  106        mv.visitInsn(Opcodes.DUP);
  107        mv.visitInsn(Opcodes.ICONST_2);
  108        InstrSupport.push(mv, probecount);
  109        mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Integer",
  110                "valueOf", "(I)Ljava/lang/Integer;");
  111        mv.visitInsn(Opcodes.AASTORE);
  112    }
  113
  114    /**
  115     * Generates the code that calls the runtime data access through the JRE API
  116     * method {@link Object#equals(Object)}. The code pops a {@link Object}
  117     * instance from the stack and pushes the probe array of type
  118     * <code>boolean[]</code> on the operand stack. The generated code requires
  119     * a stack size of 6.
  120     * 
  121     * @param classid
  122     * @param classname
  123     * @param probecount
  124     * @param mv
  125     */
  126    public static void generateAccessCall(final long classid,
  127            final String classname, final int probecount, final MethodVisitor mv) {
  128        // stack[0]: Ljava/lang/Object;
  129
  130        generateArgumentArray(classid, classname, probecount, mv);
  131
  132        // stack[1]: [Ljava/lang/Object;
  133        // stack[0]: Ljava/lang/Object;
  134
  135        mv.visitInsn(Opcodes.DUP_X1);
  136
  137        // stack[2]: [Ljava/lang/Object;
  138        // stack[1]: Ljava/lang/Object;
  139        // stack[0]: [Ljava/lang/Object;
  140
  141        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Object", "equals",
  142                "(Ljava/lang/Object;)Z");
  143        mv.visitInsn(Opcodes.POP);
  144
  145        // stack[0]: [Ljava/lang/Object;
  146
  147        mv.visitInsn(Opcodes.ICONST_0);
  148        mv.visitInsn(Opcodes.AALOAD);
  149
  150        // stack[0]: [Z
  151
  152        mv.visitTypeInsn(Opcodes.CHECKCAST, InstrSupport.DATAFIELD_DESC);
  153    }
  154
  155    /**
  156     * In violation of the regular semantic of {@link Object#equals(Object)}
  157     * this implementation is used as the interface to the execution data store.
  158     * 
  159     * @param args
  160     *            the arguments as an {@link Object} array
  161     * @return has no meaning
  162     */
  163    @Override
  164    public boolean equals(final Object args) {
  165        getExecutionData((Object[]) args);
  166        return false;
  167    }
  168
  169}