RAM购买机制结合多种合约详解
945坏男人
发表于 2022-11-12 16:42:51
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// native.hpp (newaccount definition is actually in eosio.system.cpp)
(newaccount)(updateauth)(deleteauth)(linkauth)(unlinkauth)(canceldelay)(onerror)
// eosio.system.cpp0 J0 s' w, M5 {" E; g$ P2 k6 `- y1 [
(setram)(setparams)(setpriv)(rmvproducer)(bidname)
// delegate_bandwidth.cpp2 t1 H) v' F! A1 o6 o
(buyrambytes)(buyram)(sellram)(delegatebw)(undelegatebw)(refund)
// voting.cpp% p1 j8 y- R% X3 p1 z4 Y
(regproducer)(unregprod)(voteproducer)(regproxy)+ @5 H( R/ x# g9 D3 O
// producer_pay.cpp
(onblock)(claimrewards)4 F5 e) G8 Q/ [4 L, h
ram,cpu和net操作相关方法的都定义在delegate_bandwidth.cpp,其中和RAM相关的是buyrambytes(通过指定字节数购买ram),buyram(通过指定货币购买ram)。
delegate_bandwidth.cpp& u/ K5 H' q9 f1 |: g7 f
//根据当前市场的份额,将需要购买的字节数转化为指定的EOS进行购买# \, R/ _( U5 w# {
void system_contract::buyrambytes( account_name payer, account_name receiver, uint32_t bytes ) {2 L8 v, Y8 c0 B8 c# z
//在数据库中查询RAMCORE发行量,默认为100000000000000
auto itr = _rammarket.find(S(4,RAMCORE));. Y: u6 C" F! ]4 k4 y. u- u/ O
auto tmp = *itr;# @- F8 |1 A, D4 `( v, q+ q
auto eosout = tmp.convert( asset(bytes,S(0,RAM)), CORE_SYMBOL );
//通过转化后,调用buyram使用EOS购买
buyram( payer, receiver, eosout );' _3 ?5 T; G9 \- {6 L' F
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解析
RAM的交易机制采用Bancor算法,使每字节的价格保持不变,通过中间代币(RAMCORE)来保证EOS和RAM之间的交易流通性。从上源码看首先获得RAMCORE的发行量,再通过tmp.convert方法RAM->RAMCORE,RAMCORE->EOS(CORE_SYMBOL)再调用buyram进行购买。这里的CORE_SYMBOL不一定是指EOS,查看core_symbol.hpp,发现源码内定义为SYS,也就是说在没有修改的前提下,需要提前发行SYS代币,才能进行RAM购买。
core_symbol.hpp+ K+ L/ n& @3 {; `
#define CORE_SYMBOL S(4,SYS)2 B. n5 [9 K4 s/ ~4 s6 |
delegate_bandwidth.cpp6 x9 d5 d; {4 w# {2 I( C! U$ x2 c
void system_contract::buyram(account_name payer, account_name receiver, asset quant)( k( s' H8 m5 p w) y6 @
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//验证权限& \) S T4 S4 n
require_auth(payer);
//不能为0. o3 |* p! ? k. _! @$ r
eosio_assert(quant.amount > 0, "must purchase a positive amount");" P/ O: T, }. M B
auto fee = quant;* G4 j7 Q- Q4 ~8 X. `$ {
//手续费为0.5%,如果amoun为1则手续费为1,如果小于1,则手续费在amoun 0)5 G0 W( N; ]/ |5 X5 k7 J* X Q
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INLINE_ACTION_SENDER(eosio::token, transfer)
(N(eosio.token), {payer, N(active)},
{payer, N(eosio.ramfee), fee, std::string("ram fee")});
}, {- F Z( ]; q
int64_t bytes_out;
//根据ram市场里的EOS和RAM实时汇率计算出能够购买的RAM总量
const auto &market = _rammarket.get(S(4, RAMCORE), "ram market does not exist");# |: N0 ^, C' u; G
_rammarket.modify(market, 0, [&](auto &es) {- J3 g9 B* g; b9 u7 i {8 k: m: ~9 }
//转化方法请参考下半部分+ v. \' u' v: O
bytes_out = es.convert(quant_after_fee, S(0, RAM)).amount;, }2 {1 X4 Q* @8 }" E `% v2 U
});
//剩余总量大于0判断% w, G5 k8 F% R7 m& h
eosio_assert(bytes_out > 0, "must reserve a positive amount");
//更新全局变量,总共可以使用的内存大小" Z! r6 {8 A) v8 P2 Y& K
_gstate.total_ram_bytes_reserved += uint64_t(bytes_out);* P) e; R% [1 S. i: [4 T
//更新全局变量,购买RAM冻结总金额
_gstate.total_ram_stake += quant_after_fee.amount;3 x% d& T( q# r$ A S9 I
user_resources_table userres(_self, receiver);
auto res_itr = userres.find(receiver);
if (res_itr == userres.end())
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//在userres表中添加ram相关记录; _* o- ]( N8 w/ Y, |
res_itr = userres.emplace(receiver, [&](auto &res) {6 k/ O7 b+ b1 ^) {* i* @
res.owner = receiver;
res.ram_bytes = bytes_out;
});1 v" ]/ U# s/ A6 D+ d# l/ E
}
else
{
//在userres表中修改ram相关记录
userres.modify(res_itr, receiver, [&](auto &res) {
res.ram_bytes += bytes_out;- B+ _' L. R5 {7 o: j2 {! F
});
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//更新账号的RAM拥有量; k9 [2 _. ]+ `- k+ L
set_resource_limits(res_itr->owner, res_itr->ram_bytes, res_itr->net_weight.amount, res_itr->cpu_weight.amount);
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相关注释已经在代码中,这里还会用到一个比较重要的内容,那就是代币转化为RAM的公式,此方法请参考下面, 这方面还未深入研究会在接下来补充。
exchange_state.cpp' |/ K) _. \) a- s. P. N
asset exchange_state::convert_to_exchange( connector& c, asset in ) {5 x0 J! P: Z& s8 @+ o
real_type R(supply.amount); //RAM已经售出的总量7 D- B' P& u9 h' v
real_type C(c.balance.amount+in.amount); //RAM总购买金额+本次购买的量( E' y y: h/ S* `2 u6 ^9 i
real_type F(c.weight/1000.0);( t/ E2 G3 C+ z; d- j
real_type T(in.amount);
real_type ONE(1.0);
real_type E = -R * (ONE - std::pow( ONE + T / C, F) );//换算出EOS对应的RAM量
//print( "E: ", E, "\n");0 B8 V4 L7 V% G; k* h+ L
int64_t issued = int64_t(E);( M( F/ H! z* k- v9 ^/ C- o0 ]6 m! o
supply.amount += issued;//更新RAM已经售出的总量
c.balance.amount += in.amount;//更新RAM总购买金额
return asset( issued, supply.symbol );
}
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asset exchange_state::convert( asset from, symbol_type to ) {( a/ q8 L6 i3 D+ i
auto sell_symbol = from.symbol; . R1 E! V3 O1 J- w2 s; z0 s
auto ex_symbol = supply.symbol; % x0 ~2 {8 @5 W4 b( }
auto base_symbol = base.balance.symbol;
auto quote_symbol = quote.balance.symbol;
//根据币种转化可以购买的RAM量
if( sell_symbol != ex_symbol ) {/ h# E$ {! h: g }; H5 P( V
if( sell_symbol == base_symbol ) {
from = convert_to_exchange( base, from );
} else if( sell_symbol == quote_symbol ) {
from = convert_to_exchange( quote, from );1 f& r% o8 |, J7 v( p
} else {
eosio_assert( false, "invalid sell" );* V+ X2 Q$ J. @7 |( j& s2 H
}
} else {
if( to == base_symbol ) {
from = convert_from_exchange( base, from );
} else if( to == quote_symbol ) {
from = convert_from_exchange( quote, from ); ) @1 q; s/ w" t' u2 W
} else {. \7 Y6 T+ o0 [0 k- e" J1 C
eosio_assert( false, "invalid conversion" );( V& n5 T" B7 b8 t
}
}
if( to != from.symbol )8 Q4 r6 E8 c8 S) x& ~
return convert( from, to );
return from;
}; d6 Y2 d- k) Y/ m
convert_to_exchange的转化公式如下。
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ram购买的量是一个绝对值,是根据购买EOS的金额和当前市场内ram的数量计算出来的。一般来说在ram总量不增加的情况下,一样金额的EOS,所能获得的ram会越来越少。所以如果早期你购买了ram,然后过段时间后通过sellram卖掉ram可能还能挣钱。
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