EOS 检查交易是否合约发起避免合约攻击

// code为本合约名
void check_trx(const name &code)
{
    auto tx_size = transaction_size();
    char tx[tx_size];
    auto read_size = read_transaction(tx, tx_size);
    eosio_assert( tx_size == read_size, "read_transaction failed");
    auto trx = eosio::unpack<eosio::transaction>( tx, read_size );
    eosio::action first_action = trx.actions.front();
    eosio_assert(trx.actions.size() == 1 && first_action.name == name("transfer") && first_action.account == code, "wrong transaction");
}