org.jacoco.core.internal.Java9Support.java Source code

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Here is the source code for org.jacoco.core.internal.Java9Support.java

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/*******************************************************************************
 * Copyright (c) 2009, 2016 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:
 *    Evgeny Mandrikov - initial API and implementation
 *
 *******************************************************************************/
package org.jacoco.core.internal;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.objectweb.asm.Opcodes;

/**
 * Patching for Java 9 classes, so that ASM can read them.
 */
public final class Java9Support {

    /**
     * Version of the Java 9 class file format.
     */
    public static final int V1_9 = Opcodes.V1_8 + 1;

    private Java9Support() {
    }

    /**
     * Reads all bytes from an input stream into a byte array.
     *
     * @param is
     *             the input stream to read from
     * @return a byte array containing all the bytes from the stream
     * @throws IOException
     *             if an I/O error occurs
     */
    public static byte[] readFully(final InputStream is) throws IOException {
        if (is == null) {
            throw new IllegalArgumentException();
        }
        final byte[] buf = new byte[1024];
        final ByteArrayOutputStream out = new ByteArrayOutputStream();
        while (true) {
            int r = is.read(buf);
            if (r == -1) {
                break;
            }
            out.write(buf, 0, r);
        }
        return out.toByteArray();
    }

    private static void putShort(byte[] b, int index, int s) {
        b[index] = (byte) (s >>> 8);
        b[index + 1] = (byte) s;
    }

    private static short readShort(byte[] b, int index) {
        return (short) (((b[index] & 0xFF) << 8) | (b[index + 1] & 0xFF));
    }

    /**
     * Determines whether class definition contains {@link #V1_9} version.
     *
     * @param buffer
     *             definition of the class
     * @return <code>true</code> if class definition contains Java 9 version
     */
    public static boolean isPatchRequired(byte[] buffer) {
        return readShort(buffer, 6) == V1_9;
    }

    /**
     * Returns new definition of class with version {@link Opcodes#V1_8},
     * if it has version {@link #V1_9}.
     *
     * @param buffer
     *             definition of the class
     * @return new definition of the class
     */
    public static byte[] downgradeIfRequired(byte[] buffer) {
        return isPatchRequired(buffer) ? downgrade(buffer) : buffer;
    }

    /**
     * Replaces version in the definition of class on {@link Opcodes#V1_8}.
     *
     * @param b
     *             definition of the class
     * @return new definition of the class
     */
    public static byte[] downgrade(byte[] b) {
        byte[] result = new byte[b.length];
        System.arraycopy(b, 0, result, 0, b.length);
        putShort(result, 6, Opcodes.V1_8);
        return result;
    }

    /**
     * Replaces version in the definition of class on {@link #V1_9}.
     *
     * @param b
     *             definition of the class
     */
    public static void upgrade(byte[] b) {
        putShort(b, 6, V1_9);
    }

}