Mtrace.java

/*
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 * modification, are permitted provided that the following conditions
 * are met:
 *
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 *     notice, this list of conditions and the following disclaimer.
 *
 *   - 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.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * 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 OWNER OR
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */



/* Java class to hold static methods which will be called in byte code
 *    injections of all class files.
 */

public class Mtrace {

    /* Master switch that activates methods. */

    private static int engaged = 0;

    /* At the very beginning of every method, a call to method_entry()
     *     is injected.
     */

    private static native void _method_entry(Object thr, int cnum, int mnum);
    public static void method_entry(int cnum, int mnum)
    {
        if ( engaged != 0 ) {
            _method_entry(Thread.currentThread(), cnum, mnum);
        }
    }

    /* Before any of the return bytecodes, a call to method_exit()
     *     is injected.
     */

    private static native void _method_exit(Object thr, int cnum, int mnum);
    public static void method_exit(int cnum, int mnum)
    {
        if ( engaged != 0 ) {
            _method_exit(Thread.currentThread(), cnum, mnum);
        }
    }

}