Scala example source code file (ProfilerVisitor.java)

This example Scala source code file (ProfilerVisitor.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

acc_abstract, asm, classvisitor, methodvisitor, opcodes, override, profilervisitor, string

The ProfilerVisitor.java Scala example source code

/* NEST (New Scala Test)
 * Copyright 2007-2013 LAMP/EPFL
 * @author Grzegorz Kossakowski
 */

package scala.tools.partest.javaagent;

import scala.tools.asm.ClassVisitor;
import scala.tools.asm.MethodVisitor;
import scala.tools.asm.Opcodes;

public class ProfilerVisitor extends ClassVisitor implements Opcodes {

  private static String profilerClass = "scala/tools/partest/instrumented/Profiler";

  public ProfilerVisitor(final ClassVisitor cv) {
    super(ASM4, cv);
  }

  private String className = null;

  @Override
  public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
    className = name;
    super.visit(version, access, name, signature, superName, interfaces);
  }

  public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
    // delegate the method call to the next
    // chained visitor
    MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions);
    if (!profilerClass.equals(className)) {
      // only instrument non-abstract methods
      if((access & ACC_ABSTRACT) == 0) {
        assert(className != null);
        /* The following instructions do not modify compressed stack frame map so
         * we don't need to worry about recalculating stack frame map. Specifically,
         * let's quote "ASM 4.0, A Java bytecode engineering library" guide (p. 40):
         *
         *   In order to save space, a compiled method does not contain one frame per
         *   instruction: in fact it contains only the frames for the instructions
         *   that correspond to jump targets or exception handlers, or that follow
         *   unconditional jump instructions. Indeed the other frames can be easily
         *   and quickly inferred from these ones.
         *
         * Instructions below are just loading constants and calling a method so according
         * to definition above they do not contribute to compressed stack frame map.
         */
        mv.visitLdcInsn(className);
        mv.visitLdcInsn(name);
        mv.visitLdcInsn(desc);
        mv.visitMethodInsn(INVOKESTATIC, profilerClass, "methodCalled",
            "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)V");
      }
    }
    return mv;
  }

}