How can I copy opcodes from a method to another method in Java Class file using ASM?

Question

Here are some code.

static synchronized void q(ua paramua, int paramInt) {
try {
 if (d) { if (paramInt > -16711936);
   return; }
 if (q * 514194583 > 0) { if (paramInt > -16711936);
   abf localabf = new abf(paramua);
   n.d(localabf, -984409319);
 }
 else {
   paramua.ma(false);
 }
 return; } catch (RuntimeException localRuntimeException) { throw aht.d(localRuntimeException, "ck.q(" + 41);
}
}

static synchronized void b(ua paramua)
{
  if (d) return;
  if (q * 514194583 > 0) {
    abf localabf = new abf(paramua);
    n.d(localabf, -836239689);
  }
  else {
    paramua.ma(false);
  }
}

These two methods performs equal actions. The second parameter of the first method is psudo-argument, so I want to clear original code and make this method like this...

static synchronized void q(ua paramua, int paramInt)
{
  if (d) return;
  if (q * 514194583 > 0) {
    abf localabf = new abf(paramua);
    n.d(localabf, -836239689);
  }
  else {
    paramua.ma(false);
  }
}

How can I do this action? I tried like this.

destMethodNode.instructions.clear();
destMethodNode.instructions.add(srcMethodNode.instructions);

But throws null pointer exception. What is the reason?

I would edit the source and re-compile it. It is far more likely to work. To answer your question, you cannot add a list to list, perhaps addAll() is what you intended? — Peter Lawrey, Jun 20 '12 at 14:52

score 0 · Answer 1 · answered Jun 21 '12 at 16:13

0

See "Merging Two Classes into One" section of paper from AOSD'07 linked from the ASM's project page. It provides example how to properly use MethodNode to copy method's bytecode into another method.

answered Jun 21 '12 at 16:13

Eugene Kuleshov

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How can I copy opcodes from a method to another method in Java Class file using ASM?

1 Answers1