[EOS源码分析]6.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

大家有注意到如下红色字体的log吗

$ 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...

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。

2. 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()));

}