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Rework offer amount calculation.

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Arthur Britto
2012-07-13 15:27:22 -07:00
parent 9d40598b2b
commit a3fb732e24
5 changed files with 65 additions and 46 deletions
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67
src/Amount.cpp
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@@ -737,41 +737,50 @@ uint64 STAmount::getRate(const STAmount& offerOut, const STAmount& offerIn)
return (ret << (64 - 8)) | r.getMantissa();
}
STAmount STAmount::getClaimed(STAmount& offerOut, STAmount& offerIn, STAmount& paid)
{ // if someone is offering (offerOut) for (offerIn), and I pay (paid), how much do I get?
// Taker gets all taker can pay for with saTakerFunds, limited by saOfferPays and saOfferFunds.
// --> saOfferFunds: Limit for saOfferPays
// --> saTakerFunds: Limit for saOfferGets
// --> saOfferPays: Request : this should be reduced as the offer is fullfilled.
// --> saOfferGets: Request : this should be reduced as the offer is fullfilled.
// --> saTakerPays: Total : Used to know the approximate ratio of the exchange.
// --> saTakerGets: Total : Used to know the approximate ratio of the exchange.
// <-- saTakerPaid: Actual
// <-- saTakerGot: Actual
// <-- bRemove: remove offer it is either fullfilled or unfunded
bool STAmount::applyOffer(
const STAmount& saOfferFunds, const STAmount& saTakerFunds,
const STAmount& saOfferPays, const STAmount& saOfferGets,
const STAmount& saTakerPays, const STAmount& saTakerGets,
STAmount& saTakerPaid, STAmount& saTakerGot)
{
saOfferGets.throwComparable(saTakerPays);
offerIn.throwComparable(paid);
assert(!saOfferFunds.isZero() && !saTakerFunds.isZero()); // Must have funds.
assert(!saOfferGets.isZero() && !saOfferPays.isZero()); // Must not be a null offer.
if (offerIn.isZero() || offerOut.isZero())
{ // If the offer is invalid or empty, you pay nothing and get nothing and the offer is dead
offerIn.zero();
offerOut.zero();
paid.zero();
return STAmount();
}
// Amount offer can pay out, limited by offer and funds.
STAmount saOfferPaysAvailable = saOfferFunds < saOfferPays ? saOfferFunds : saOfferPays;
// If you pay nothing, you get nothing. Offer is untouched
if (paid.isZero()) return STAmount();
// Amount offer needs to get to be complete, limited by offer funds.
STAmount saOfferGetsAvailable =
saOfferFunds == saOfferPays
? saOfferGets // Offer was fully funded, avoid shenanigans.
: divide(multiply(saTakerPays, saOfferPaysAvailable, uint160(1)), saTakerGets, saOfferGets.getCurrency());
if (paid >= offerIn)
{ // If you pay equal to or more than the offer amount, you get the whole offer and pay its input
STAmount ret(offerOut);
paid = offerIn;
offerOut.zero();
offerIn.zero();
return ret;
}
// partial satisfaction of a normal offer
STAmount ret = divide(multiply(paid, offerOut, uint160(1)), offerIn, offerOut.getCurrency());
offerOut -= ret;
offerIn -= paid;
if (offerOut.isZero() || offerIn.isZero())
if (saTakerFunds >= saOfferGetsAvailable)
{
offerIn.zero();
offerOut.zero();
// Taker gets all of offer available.
saTakerPaid = saOfferGetsAvailable; // Taker paid what offer could get.
saTakerGot = saOfferPaysAvailable; // Taker got what offer could pay.
return true; // No left over offer.
}
return ret;
// Taker only get's a portion of offer.
saTakerPaid = saTakerFunds; // Taker paid all he had.
saTakerGot = divide(multiply(saTakerFunds, saOfferPaysAvailable, uint160(1)), saOfferGetsAvailable, saOfferPays.getCurrency());
return saTakerGot >= saOfferPaysAvailable;
}
STAmount STAmount::getPay(const STAmount& offerOut, const STAmount& offerIn, const STAmount& needed)