edu.berkeley.cs.jqf.fuzz.util.Coverage Maven / Gradle / Ivy

/*
 * Copyright (c) 2017-2018 The Regents of the University of California
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package edu.berkeley.cs.jqf.fuzz.util;

import java.util.ArrayList;
import java.util.Collection;

import edu.berkeley.cs.jqf.instrument.tracing.events.BranchEvent;
import edu.berkeley.cs.jqf.instrument.tracing.events.CallEvent;
import edu.berkeley.cs.jqf.instrument.tracing.events.TraceEvent;
import edu.berkeley.cs.jqf.instrument.tracing.events.TraceEventVisitor;

/**
 * Utility class to collect branch and function coverage
 *
 * @author Rohan Padhye
 */
public class Coverage implements TraceEventVisitor {

    /** The size of the coverage map. */
    private final int COVERAGE_MAP_SIZE = (1 << 16) - 1; // Minus one to reduce collisions

    /** The coverage counts for each edge. */
    private final Counter counter = new NonZeroCachingCounter(COVERAGE_MAP_SIZE);

    /** Creates a new coverage map. */
    public Coverage() {

    }

    /**
     * Creates a copy of an existing coverage map.
     *
     * @param that the coverage map to copy
     */
    public Coverage(Coverage that) {
        for (int idx = 0; idx < COVERAGE_MAP_SIZE; idx++) {
            this.counter.setAtIndex(idx, that.counter.getAtIndex(idx));
        }
    }

    /**
     * Returns the size of the coverage map.
     *
     * @return the size of the coverage map
     */
    public int size() {
        return COVERAGE_MAP_SIZE;
    }

    /**
     * Updates coverage information based on emitted event.
     *
     * This method updates its internal counters for branch and
     * call events.
     *
     * @param e the event to be processed
     */
    public void handleEvent(TraceEvent e) {
        e.applyVisitor(this);
    }

    @Override
    public void visitBranchEvent(BranchEvent b) {
        counter.increment(b.getIid() * 31 + b.getArm());
    }

    @Override
    public void visitCallEvent(CallEvent e) {
        counter.increment(e.getIid());
    }

    /**
     * Returns the number of edges covered.
     *
     * @return the number of edges with non-zero counts
     */
    public int getNonZeroCount() {
        return counter.getNonZeroSize();
    }

    /**
     * Returns a collection of branches that are covered.
     *
     * @return a collection of keys that are covered
     */
    public Collection getCovered() {
        return counter.getNonZeroIndices();
    }


    public Collection computeNewCoverage(Coverage baseline) {
        Collection newCoverage = new ArrayList<>();
        for (int idx : this.counter.getNonZeroIndices()) {
            if (baseline.counter.getAtIndex(idx) == 0) {
                newCoverage.add(idx);
            }
        }
        return newCoverage;

    }



    /**
     * Clears the coverage map.
     */
    public void clear() {
        this.counter.clear();
    }

    private static int[] HOB_CACHE = new int[1024];

    /** Computes the highest order bit */
    private static int computeHob(int num)
    {
        if (num == 0)
            return 0;

        int ret = 1;

        while ((num >>= 1) != 0)
            ret <<= 1;

        return ret;
    }

    /** Populates the HOB cache. */
    static {
        for (int i = 0; i < HOB_CACHE.length; i++) {
            HOB_CACHE[i] = computeHob(i);
        }
    }

    /** Returns the highest order bit (perhaps using the cache) */
    private static int hob(int num) {
        if (num < HOB_CACHE.length) {
            return HOB_CACHE[num];
        } else {
            return computeHob(num);
        }
    }


    /**
     * Updates this coverage with bits from the parameter.
     *
     * @param that the run coverage whose bits to OR
     *
     * @return true iff that is not a subset
     *         of this, causing this to change.
     */
    public boolean updateBits(Coverage that) {
        boolean changed = false;
        for (int idx = 0; idx < COVERAGE_MAP_SIZE; idx++) {
            int before = this.counter.getAtIndex(idx);
            int after = before | hob(that.counter.getAtIndex(idx));
            if (after != before) {
                this.counter.setAtIndex(idx, after);
                changed = true;
            }
        }
        return changed;
    }


}