EOS源码学习（二）：DPOS投票模块

需要首先理解的名词

1. state

2. band width

3. bid

首先看下 contracts\eosio.system.hpp ：system_contract

这个文件是关于 投票和唱票的过程代码

class system_contract : public native {
         //投票人
         voters_table           _voters;
         //生产者，类似ethereum中的validator
         producers_table        _producers;
         //世界状态机
         global_state_singleton _global;
          //和band_width相关，暂时还不知道做什么用
         rammarket              _rammarket;
        
         void onblock( block_timestamp timestamp, account_name producer );
/*delegate_bandwidth.cpp*/                
         //记录from账户和receiver账户之间因为这次delegate而发生的状态机的转换，
         //如果transfer为true，receiver可以回滚状态机，否则from可以回滚，在任何时候    
         //bw : band width
         void delegatebw( account_name from, account_name receiver,
                          asset stake_net_quantity, asset stake_cpu_quantity, bool transfer );

         //撤销 delegate操作，并释放资源
         //如果delegate操作已经执行，那么会执行一个 send the tokens back to 'from'
         //from账户调用该接口之后，就丧失了投票权，所有生产者的记录都会更新
         void undelegatebw( account_name from, account_name receiver,
                            asset unstake_net_quantity, asset unstake_cpu_quantity );
     
/*voting.cpp*/ 
        ...
   };

以上这些接口都是通过main函数中 action的方式创建
example: eos\programs\cleos\main.cpp

auto undelegate_bandwidth = actionRoot->add_subcommand("undelegatebw", localized("Undelegate bandwidth"));
undelegate_bandwidth->add_option("from", from_str, localized("The account undelegating bandwidth"))->required();
undelegate_bandwidth->add_option("receiver", receiver_str, localized("The account to undelegate bandwidth from"))->required();
undelegate_bandwidth->add_option("unstake_net_quantity", unstake_net_amount, localized("The amount of EOS to undelegate for network bandwidth"))->required();
undelegate_bandwidth->add_option("unstake_cpu_quantity", unstake_cpu_amount, localized("The amount of EOS to undelegate for CPU bandwidth"))->required();
add_standard_transaction_options(undelegate_bandwidth);