typedef struct acnts {
    account_name name0;
    account_name name1;
    account_name name2;
    account_name name3;
} account_names;

void batchtransfer(symbol_name symbol, account_name from, account_names to, uint64_t balance)
{
    require_auth(from);
    account fromaccount;

    require_recipient(from);
    require_recipient(to.name0);
    require_recipient(to.name1);
    require_recipient(to.name2);
    require_recipient(to.name3);

    eosio_assert(is_balance_within_range(balance), "invalid balance");
    eosio_assert(balance > 0, "must transfer positive balance");

    uint64_t amount = balance * 4; //乘法溢出

    int itr = db_find_i64(_self, symbol, N(table), from);
    eosio_assert(itr >= 0, "Sub-- wrong name");
    db_get_i64(itr, &fromaccount, (account));
    eosio_assert(fromaccount.balance >= amount, "overdrawn balance");

    sub_balance(symbol, from, amount);

    add_balance(symbol, to.name0, balance);
    add_balance(symbol, to.name1, balance);
    add_balance(symbol, to.name2, balance);
    add_balance(symbol, to.name3, balance);
}

void token::transfer( account_name from,
                      account_name to,
                      asset        quantity,
                      string       memo )
{
    eosio_assert( from != to, "cannot transfer to self" );
    eosio_assert( is_account( to ), "to account does not exist");
    auto sym = quantity.symbol.name();
    stats statstable( _self, sym );
    const auto& st = statstable.get( sym );

    require_recipient( from );
    require_recipient( to );

    eosio_assert( quantity.is_valid(), "invalid quantity" );
    eosio_assert( quantity.amount > 0, "must transfer positive quantity" );
    eosio_assert( quantity.symbol == st.supply.symbol, "symbol precision mismatch" );
    eosio_assert( memo.size() <= 256, "memo has more than 256 bytes" );

    auto payer = has_auth( to ) ? to : from;

    sub_balance( from, quantity );
    add_balance( to, quantity, payer );
}

// extend from EOSIO_ABI
#define EOSIO_ABI_EX( TYPE, MEMBERS ) \
extern "C" { \
   void apply( uint64_t receiver, uint64_t code, uint64_t action ) { \
      auto self = receiver; \
      if( action == N(onerror)) { \
         /* onerror is only valid if it is for the "eosio" code account and authorized by "eosio"'s "active permission */ \
         eosio_assert(code == N(eosio), "onerror action's are only valid from the \"eosio\" system account"); \
      } \
      if( code == self || code == N(eosio.token) || action == N(onerror) ) { \
         TYPE thiscontract( self ); \
         switch( action ) { \
            EOSIO_API( TYPE, MEMBERS ) \
         } \
         /* does not allow destructor of thiscontract to run: eosio_exit(0); */ \
      } \
   } \
}

EOSIO_ABI_EX(eosio::charity, (hi)(transfer))

// source code: https://gitlab.com/EOSBetCasino/eosbetdice_public/blob/master/EOSBetDice.cpp#L115
void transfer(uint64_t sender, uint64_t receiver) {

	auto transfer_data = unpack_action_data<st_transfer>();

	if (transfer_data.from == _self || transfer_data.from == N(eosbetcasino)){
		return;
	}

	eosio_assert( transfer_data.quantity.is_valid(), "Invalid asset");
}

// source code: https://github.com/loveblockchain/eosdice/blob/3c6f9bac570cac236302e94b62432b73f6e74c3b/eosbocai2222.hpp#L174
uint8_t random(account_name name, uint64_t game_id)
{
    auto eos_token = eosio::token(N(eosio.token));
    asset pool_eos = eos_token.get_balance(_self, symbol_type(S(4, EOS)).name());
    asset ram_eos = eos_token.get_balance(N(eosio.ram), symbol_type(S(4, EOS)).name());
    asset betdiceadmin_eos = eos_token.get_balance(N(betdiceadmin), symbol_type(S(4, EOS)).name());
    asset newdexpocket_eos = eos_token.get_balance(N(newdexpocket), symbol_type(S(4, EOS)).name());
    asset chintailease_eos = eos_token.get_balance(N(chintailease), symbol_type(S(4, EOS)).name());
    asset eosbiggame44_eos = eos_token.get_balance(N(eosbiggame44), symbol_type(S(4, EOS)).name());
    asset total_eos = asset(0, EOS_SYMBOL);
    //攻击者可通过inline_action改变余额total_eos，从而控制结果
    total_eos = pool_eos + ram_eos + betdiceadmin_eos + newdexpocket_eos + chintailease_eos + eosbiggame44_eos;
    auto mixd = tapos_block_prefix() * tapos_block_num() + name + game_id - current_time() + total_eos.amount;
    const char *mixedChar = reinterpret_cast<const char *>(&mixd);

    checksum256 result;
    sha256((char *)mixedChar, sizeof(mixedChar), &result);

    uint64_t random_num = *(uint64_t *)(&result.hash[0]) + *(uint64_t *)(&result.hash[8]) + *(uint64_t *)(&result.hash[16]) + *(uint64_t *)(&result.hash[24]);
    return (uint8_t)(random_num % 100 + 1);
}