Hello,

i'm working with javassist for quite some time now and I must say it is really impressive what this thing can do, and with what ease!

Anyways, I'm confronted with one problem:
My tool inserts an arbitrary series of conditional branches and some code afterwards. This means I have to precalculate the number of bytes inserted for all following conditions and the code in respect to set the branch offset. All works well unless I load a string constant using addLdc(String). In this case I am unable to precalculate whether there are 3 bytes (ldc) or 4 bytes (ldc_w) inserted, since this depends on the ConstTables state at insertion time.

I've developed a workaround for my case by extending the Bytecode class and altering its behaviour with

private ArrayList<Integer> m_branches;
...

public void addBranch(int code, int branchOffset) {
 // branch opcode is inserted at offset getSize()
 m_branches.add(getSize());
 addOpcode(code);
 add16bit(branchOffset);
}

private void adjustBranches(int end, int shift) {
 for (Integer pos : m_branches) {
 int branchOffset = read16bit(pos + 1);
 if ((pos + branchOffset) <= end) continue;
 write16bit(pos + 1, branchOffset + shift);
 }
}

@Override
public void addLdc(int i) {
 if (i > 0xFF) {
 adjustBranches(getSize(), 1);
 addOpcode(LDC_W);
 addIndex(i);
 } else {
 addOpcode(LDC);
 add(i);
 }
}

I think this is could be extended to a general solution, if it would be well defined how many bytes one should asume to be inserted.

Is there a way around this problem that I've overseen or is this really a "bug"?

---

By the way, is there any reason there is no

public void add16bit(int value) {
 value = value % 65536;
 add(value >> 8);
 add(value % 256);
}

defined in Bytecode? Since it is required for inserting branch offsets...