EOS REX 安全系列之从源码开始玩转 REX(二)

void system_contract::sellrex( const name& from, const asset& rex )   {      require_auth( from );
      runrex(2);
      auto bitr = _rexbalance.require_find( from.value, "user must first buyrex" );      check( rex.amount > 0 && rex.symbol == bitr->rex_balance.symbol,             "asset must be a positive amount of (REX, 4)" );      process_rex_maturities( bitr ); ///先收获成熟的rex      check( rex.amount <= bitr->matured_rex, "insufficient available rex" );///只能卖成熟的rex
      auto current_order = fill_rex_order( bitr, rex );///拿到出租EOS得到的分红      asset pending_sell_order = update_rex_account( from, current_order.proceeds, current_order.stake_change );      //订单状态不成功      if ( !current_order.success ) {         /**          * REX order couldn't be filled and is added to queue.          * If account already has an open order, requested rex is added to existing order.          */         auto oitr = _rexorders.find( from.value );         if ( oitr == _rexorders.end() ) {            oitr = _rexorders.emplace( from, [&]( auto& order ) {               order.owner         = from;               order.rex_requested = rex;               order.is_open       = true;               order.proceeds      = asset( 0, core_symbol() );               order.stake_change  = asset( 0, core_symbol() );               order.order_time    = current_time_point();            });         } else {            _rexorders.modify( oitr, same_payer, [&]( auto& order ) {               order.rex_requested.amount += rex.amount;            });         }         pending_sell_order.amount = oitr->rex_requested.amount;       }      check( pending_sell_order.amount <= bitr->matured_rex, "insufficient funds for current and scheduled orders" );      // dummy action added so that sell order proceeds show up in action trace      if ( current_order.success ) {         dispatch_inline( null_account, "sellresult"_n, { }, std::make_tuple( current_order.proceeds ) );      }   }

rex_order_outcome system_contract::fill_rex_order( const rex_balance_table::const_iterator& bitr, const asset& rex )   {      auto rexitr = _rexpool.begin();      const int64_t S0 = rexitr->total_lendable.amount;      const int64_t R0 = rexitr->total_rex.amount;      const int64_t p  = (uint128_t(rex.amount) * S0) / R0; ///越多人借用资源收益越高      const int64_t R1 = R0 - rex.amount; ///更新rex pool中rex的数量      const int64_t S1 = S0 - p; ///更新rex pool中EOS的数量      asset proceeds( p, core_symbol() ); ///获得的收益      asset stake_change( 0, core_symbol() );      bool  success = false; ///默认订单完成状态为0
      check( proceeds.amount > 0, "proceeds are negligible" );
      const int64_t unlent_lower_bound = rexitr->total_lent.amount;      //计算能未质押的rex pool中的EOS的数量，用于接下来观察是否足够支付用户产生的rex利润      const int64_t available_unlent   = rexitr->total_unlent.amount - unlent_lower_bound; // available_unlent <= 0 is possible       //rexpool中的钱足够支付rex利润      if ( proceeds.amount <= available_unlent ) {         const int64_t init_vote_stake_amount = bitr->vote_stake.amount;         const int64_t current_stake_value    = ( uint128_t(bitr->rex_balance.amount) * S0 ) / R0;         _rexpool.modify( rexitr, same_payer, [&]( auto& rt ) {            rt.total_rex.amount      = R1;///更新rex pool中的rex的数量            rt.total_lendable.amount = S1; ///更新lenableEOS数量            rt.total_unlent.amount   = rt.total_lendable.amount - rt.total_lent.amount; ///减少unlent数据         });         //对用户的rexbalance账户进行操作         _rexbalance.modify( bitr, same_payer, [&]( auto& rb ) {            rb.vote_stake.amount   = current_stake_value - proceeds.amount;            rb.rex_balance.amount -= rex.amount;            rb.matured_rex        -= rex.amount; ///减少已经成熟的rex的数量         });         stake_change.amount = bitr->vote_stake.amount - init_vote_stake_amount;         success = true;      ///不够钱支付的情况      } else {         proceeds.amount = 0;      }
      return { success, proceeds, stake_change };   }