[EOS源码分析] EOS特殊智能合约eosio

这里说的eosio智能合约不是泛指eos的智能合约，它是一个特殊的具体的合约。它本事可大了，我们一起来看看它有哪些功能

负责智能合约部署

$ cleos set contract hello.code ../eos-contract/hello -p hello.code
Publishing contract...
executed transaction: daabe65267af4b9a11e5ff90a165bbaac68469630f499bcea1ef0eb7da6d970c  1792 bytes  2558 us
#         eosio <= eosio::setcode               {"account":"hello.code","vmtype":0,"vmversion":0,"code":"0061736d01000000013b0c60027f7e006000017e600...
#         eosio <= eosio::setabi                {"account":"hello.code","abi":"00010c6163636f756e745f6e616d65046e616d6501026869000104757365720c61636...

注意下 eosio <= eosio::setcode和eosio <= eosio::setabi
这段log很明显的说明了

$ cleos set contract eosio build/contracts/eosio.bios -p eosio

等价于调用eosio智能合约的setcode和setabi函数

$ cleos push action eosio setcode '[eosio.bios.wasm]' -p eosio
$ cleos push action eosio setabi eosio '[eosio.bios.abi] -p eosio

也就说合约部署是通过调用eosio合约来实现的
对应的源码：
set contract会产生setcode和setabi两个action

add_standard_transaction_options(contractSubcommand, "account@active");
   add_standard_transaction_options(codeSubcommand, "account@active");
   add_standard_transaction_options(abiSubcommand, "account@active");
   contractSubcommand->set_callback([&] {
      shouldSend = false;
      set_code_callback();
      set_abi_callback();
      std::cout << localized("Publishing contract...") << std::endl;
      send_actions(std::move(actions), 10000, packed_transaction::zlib);
   });

chain::action create_setcode(const name& account, const bytes& code) {
   return action {
      tx_permission.empty() ? vector<chain::permission_level>{{account,config::active_name}} : get_account_permissions(tx_permission),
      setcode{
         .account   = account,
         .vmtype    = 0,
         .vmversion = 0,
         .code      = code
      }
   };
}

struct setcode {
   account_name                     account;
   uint8_t                          vmtype = 0;
   uint8_t                          vmversion = 0;
   bytes                            code;

   static account_name get_account() {
      return config::system_account_name;
   }

   static action_name get_name() {
      return N(setcode);
   }
};

const static uint64_t system_account_name    = N(eosio);

set_code和set_abi都是通过调用system_account_name即eosio智能合约来执行的

负责账号创建

同样我们看看create account，其实就是调用eosio合约的newaccount函数

$ cleos create account eosio hello.code EOS7KBTMkUq4VPakqsZUnZfBbMbS2U7cn9qSa3q6G5ZzEeUeNSVgv EOS7KBTMkUq4VPakqsZUnZfBbMbS2U7cn9qSa3q6G5ZzEeUeNSVgv
executed transaction: 01aff4356a6277eec777494fc6aeaf97164c53997c46fe853247ed7e100f4987  200 bytes  911 us
#         eosio <= eosio::newaccount            {"creator":"eosio","name":"hello.code","owner":{"threshold":1,"keys":[{"key":"EOS7KBTMkUq4VPakqsZUnZ...

负责权限管理

这次是调用eosio的updateauth函数

$ cleos set account permission testaccount active '{"threshold" : 1, "keys" : [], "accounts" : [{"permission":{"actor":"bob","permission":"active"},"weight":1}, {"permission":{"actor":"stacy","permission":"active"},"weight":1}]}’ owner
executed transaction: b1bc9680a9ba615a6de8c3f7c692d7d28ff97edae245bb40f948692b14ea6c15  160 bytes  189 us
#         eosio <= eosio::updateauth            {"account":"testaccount","permission":"active","parent":"owner","auth":{"threshold":1,"keys":[],"acc...
warning: transaction executed locally, but may not be confirmed by the network yet

蛋生鸡，鸡生蛋问题

既然eosio是一个智能合约，而它又负责合约部署，那它自己是谁部署的呢？我们先来看下这个结构图

eosio contract负责系统服务，比如部署合约，创建账号。infra contracts层比如eosio.token和eosio.msig类似库作用的合约，比如多签名，发行代币，方便dapp层使用。Dapp才是用户直接接触的，每个开发人员编写程序然后部署，这些程序都是DApp。

eosio contract由3个部分构成

nativeaction

nativeactions就是前面提到的setcode, setabi, newaccount功能的函数集。这部分代码是hardcode在EOS系统代码里的，也就说不需要部署这一步骤，所以就解决了蛋生鸡，鸡生蛋问题。

eosio.bios, eosio.system
eosio.bios是一个智能合约的代码，是通过智能合约部署方式绑定到eosio contract上的。那你可能会说，eosio.bios部署后，nativeactions部分是不是就失效了啊。确实可以这样实现，由于setcode这些action需要永久生效，这就需要eosio.bios包含nativeactions这些函数，这样就出现了相同一份代码分散在两个模块，独立性和维护不够好。所以，目前的实现是通过特殊处理让nativeactions的函数有最高优先级，永不覆盖，哪怕eosio.bios实现了同样的函数(比如set_code, set_abi)。但是eosio.system和eosio.bios是一个级别的，都是contract, 是水火不相容的，一旦将eosio.system绑定到eosio这个账号，eosio.bios就失效了，所以eosio.bios的函数要么是临时用途的，要么就需要bios.system重新实现，比如setalimits会失效，而setpriv会在eosio.system重新实现。这个和cpu启动一样，一开始bios(bootloader)代码运行，然后引导system代码，当system加载后，bios(bootloader)代码失效。所以从这个设计和名字可以看出，EOS确实是在按照操作系统的逻辑设计。

eosio.bios的接口

EOSIO_ABI( eosio::bios, (setpriv)(setalimits)(setglimits)(setprods)(reqauth) )

eosio.sytem的接口

EOSIO_ABI( eosiosystem::system_contract,
(setram)
// delegate_bandwith.cpp
(delegatebw)(undelegatebw)(refund)
(buyram)(buyrambytes)(sellram)
// voting.cpp
// producer_pay.cpp
(regproxy)(regproducer)(unregprod)(voteproducer)
(claimrewards)
// native.hpp
(onblock)
(newaccount)(updateauth)(deleteauth)(linkauth)(unlinkauth)(postrecovery)(passrecovery)(vetorecovery)(onerror)(canceldelay)
//this file
(setpriv)
)

nativeaction解读

nativeaction注册

nativeaction是通过SET_APP_HANDLER注册的

#define SET_APP_HANDLER( receiver, contract, action) \
   set_apply_handler( #receiver, #contract, #action, &BOOST_PP_CAT(apply_, BOOST_PP_CAT(contract, BOOST_PP_CAT(_,action) ) ) )

   SET_APP_HANDLER( eosio, eosio, newaccount );
   SET_APP_HANDLER( eosio, eosio, setcode );
   SET_APP_HANDLER( eosio, eosio, setabi );
   SET_APP_HANDLER( eosio, eosio, updateauth );
   SET_APP_HANDLER( eosio, eosio, deleteauth );
   SET_APP_HANDLER( eosio, eosio, linkauth );
   SET_APP_HANDLER( eosio, eosio, unlinkauth );
/*
   SET_APP_HANDLER( eosio, eosio, postrecovery );
   SET_APP_HANDLER( eosio, eosio, passrecovery );
   SET_APP_HANDLER( eosio, eosio, vetorecovery );
*/

   SET_APP_HANDLER( eosio, eosio, canceldelay );
   void set_apply_handler( account_name receiver, account_name contract, action_name action, apply_handler v ) {
      apply_handlers[receiver][make_pair(contract,action)] = v;
   }

对应的函数名是apply_eosio_xxx,比如apply_eosio_setcode,apply_eosio_newaccount

nativeaction函数调用

系统会先检测action的名字是否注册在native handler里，如果在则直接调用，不在的话，执行合约代码，并跳转到相应的action函数

    class apply_context { 
        { 
        public:
          apply_context(controller& con, transaction_context& trx_ctx, const action& a, uint32_t depth=0)
          :control(con)
          ,db(con.db())
          ,trx_context(trx_ctx)
          ,act(a)
          //合约的账号
          ,receiver(act.account)
          ,used_authorizations(act.authorization.size(), false)
    }

    action_trace apply_context::exec_one()
    {
       auto start = fc::time_point::now();

       const auto& cfg = control.get_global_properties().configuration;
       try {
          //获取智能合约对象
          const auto &a = control.get_account(receiver);
          privileged = a.privileged;
          //检测该action是否是native action,如果是则调用native handler
          auto native = control.find_apply_handler(receiver, act.account, act.name);
          if (native) {
             //hative handler(action)存在，则调用
             (*native)(*this);
          }
          //只要不是setcode调用，允许nativehandler和contract部署的代码都执行
          if( a.code.size() > 0
              && !(act.account == config::system_account_name && act.name == N(setcode) && receiver == config::system_account_name) ) {
             try {
                control.get_wasm_interface().apply(a.code_version, a.code, *this);
             } catch ( const wasm_exit& ){}
          }
         ….

       } FC_CAPTURE_AND_RETHROW((_pending_console_output.str()));
    }

转载自:http://blog.csdn.net/itleaks

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