TxOut BlockDataViewer::getPrevTxOut(TxIn & txin) const
{
   if (txin.isCoinbase())
      return TxOut();

   OutPoint op = txin.getOutPoint();
   Tx theTx = getTxByHash(op.getTxHash());
   if (!theTx.isInitialized())
      throw runtime_error("couldn't find prev tx");

   uint32_t idx = op.getTxOutIndex();
   return theTx.getTxOutCopy(idx);
}