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)6 `; N! Y# N6 \0 P* K$ ^9 [1 m
(newaccount)(updateauth)(deleteauth)(linkauth)(unlinkauth)(canceldelay)(onerror)* Q; G: `7 S# c; A+ b
// eosio.system.cpp6 z! B1 g# Q& Z/ ?# L$ z, C
(setram)(setparams)(setpriv)(rmvproducer)(bidname)
// delegate_bandwidth.cpp6 Z5 H4 R j5 H- _/ y) p, \) D3 }
(buyrambytes)(buyram)(sellram)(delegatebw)(undelegatebw)(refund)
// voting.cpp
(regproducer)(unregprod)(voteproducer)(regproxy)7 O, m }. {" J! \* i% {3 r
// producer_pay.cpp
(onblock)(claimrewards)5 S3 i: I+ k% I% Q5 W
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)。+ u; p N* |7 E
delegate_bandwidth.cpp- j% R0 A& y' S' i" J
//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
void system_contract::buyrambytes( account_name payer, account_name receiver, uint32_t bytes ) {, _& g! S& F' y. J8 s! Z1 p
//在数据库中查询RAMCORE发行量,默认为100000000000000
auto itr = _rammarket.find(S(4,RAMCORE));
auto tmp = *itr;
auto eosout = tmp.convert( asset(bytes,S(0,RAM)), CORE_SYMBOL );
//通过转化后,调用buyram使用EOS购买) l1 O/ ?' U. z) E+ G
buyram( payer, receiver, eosout );
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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。7 Y0 R' U( ~( R6 H& U# D% Q* ^
core_symbol.hpp
#define CORE_SYMBOL S(4,SYS)
delegate_bandwidth.cpp9 g) Z5 c( t! I
void system_contract::buyram(account_name payer, account_name receiver, asset quant)9 h" q& n1 U6 }' ]7 E
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//验证权限! u8 v, I+ L; D9 v1 W+ n
require_auth(payer);7 _4 E6 q3 V, T# x0 L% a) i
//不能为0) y" t4 T1 p# T0 y5 L1 F
eosio_assert(quant.amount > 0, "must purchase a positive amount");
auto fee = quant;
//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): z: V+ ~$ w. w
{
INLINE_ACTION_SENDER(eosio::token, transfer)0 k2 {3 b3 z2 F+ r2 I6 e
(N(eosio.token), {payer, N(active)},
{payer, N(eosio.ramfee), fee, std::string("ram fee")});
}
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");# A5 r$ o# E! X
_rammarket.modify(market, 0, [&](auto &es) {
//转化方法请参考下半部分! F& p2 X& r0 O
bytes_out = es.convert(quant_after_fee, S(0, RAM)).amount;7 O5 E- J0 c- R/ c# w6 x" M( z
});
//剩余总量大于0判断
eosio_assert(bytes_out > 0, "must reserve a positive amount");% y4 R: U& E. {7 G! f# o5 N/ n
//更新全局变量,总共可以使用的内存大小3 u6 B8 }, A+ M4 F' M3 ?
_gstate.total_ram_bytes_reserved += uint64_t(bytes_out);# h n2 P2 e" i( l) [7 n' t
//更新全局变量,购买RAM冻结总金额
_gstate.total_ram_stake += quant_after_fee.amount;
user_resources_table userres(_self, receiver);3 Z8 _/ e, Q L1 x1 h
auto res_itr = userres.find(receiver);
if (res_itr == userres.end())7 y" p( j. Q6 M4 S: L- z
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//在userres表中添加ram相关记录6 _0 Y( x, v O: d8 e
res_itr = userres.emplace(receiver, [&](auto &res) {
res.owner = receiver;
res.ram_bytes = bytes_out;/ y0 I c7 |! J- j, l7 n, `
});
}
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//在userres表中修改ram相关记录
userres.modify(res_itr, receiver, [&](auto &res) {
res.ram_bytes += bytes_out;- u8 K G$ p6 j
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}
//更新账号的RAM拥有量
set_resource_limits(res_itr->owner, res_itr->ram_bytes, res_itr->net_weight.amount, res_itr->cpu_weight.amount);/ U" o( \; M5 j$ y) [
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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。4 V( L1 D5 n: I) |6 P6 i
exchange_state.cpp) h; W) }8 ]0 a/ e6 K ]7 ?' X$ x
asset exchange_state::convert_to_exchange( connector& c, asset in ) {# f4 H2 z3 E' O v' j$ v
real_type R(supply.amount); //RAM已经售出的总量
real_type C(c.balance.amount+in.amount); //RAM总购买金额+本次购买的量- R. d4 P8 |6 ]7 a$ G
real_type F(c.weight/1000.0);1 T7 @" N7 ~# K/ \. `, |
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0 h! R1 e0 y C" u" E3 Y, l, o& i; G
//print( "E: ", E, "\n");
int64_t issued = int64_t(E);8 |6 o$ k! z( W6 Z
supply.amount += issued;//更新RAM已经售出的总量# j% J1 r4 I3 e, X* M
c.balance.amount += in.amount;//更新RAM总购买金额
return asset( issued, supply.symbol );
}! t+ @, W3 S+ O- ~) m1 k$ T
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asset exchange_state::convert( asset from, symbol_type to ) {
auto sell_symbol = from.symbol;
auto ex_symbol = supply.symbol; " f5 { Z2 i5 i7 i; V6 X
auto base_symbol = base.balance.symbol; * C& {- a/ t& E) y" h+ ?9 m: T! h
auto quote_symbol = quote.balance.symbol;
//根据币种转化可以购买的RAM量
if( sell_symbol != ex_symbol ) {
if( sell_symbol == base_symbol ) {
from = convert_to_exchange( base, from );
} else if( sell_symbol == quote_symbol ) {
from = convert_to_exchange( quote, from );
} else {
eosio_assert( false, "invalid sell" );
}
} else {1 B9 {. E3 D" m7 j
if( to == base_symbol ) {4 m# \) n# [* u+ w: d/ R. m5 v2 r
from = convert_from_exchange( base, from );
} else if( to == quote_symbol ) {$ e" z) R- b! ]* w% \( A2 s
from = convert_from_exchange( quote, from );
} else {
eosio_assert( false, "invalid conversion" );
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if( to != from.symbol ) \: N1 q* z( y0 `; q4 ?
return convert( from, to );& Z2 o& w0 I: p! K$ B, G1 c- H+ Z
return from; Z# X3 C. j6 K( c
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convert_to_exchange的转化公式如下。
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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