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Simplify fee handling during transaction submission:

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Avoid custom overflow code; simply use 128-bit math to
maintain precision and return a saturated 64-bit value
as the final result.

Disallow use of negative values in the `fee_mult_max`
and `fee_div_max` fields. This change could potentially
cause submissions with negative values that would have
previously succeeded to now fail.
This commit is contained in:
Nik Bougalis
2017-01-18 03:33:46 -08:00
parent c7de7950c4
commit 8345475bc3
8 changed files with 135 additions and 106 deletions
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47
src/ripple/app/misc/impl/LoadFeeTrack.cpp
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@@ -21,11 +21,12 @@
#include <ripple/app/misc/LoadFeeTrack.h>
#include <ripple/basics/contract.h>
#include <ripple/basics/Log.h>
#include <ripple/basics/mulDiv.h>
#include <ripple/core/Config.h>
#include <ripple/ledger/ReadView.h>
#include <ripple/protocol/STAmount.h>
#include <ripple/protocol/JsonFields.h>
#include <cstdint>
#include <type_traits>
namespace ripple {
@@ -80,11 +81,47 @@ LoadFeeTrack::lowerLocalFee ()
//------------------------------------------------------------------------------
// Scale from fee units to millionths of a ripple
std::uint64_t
scaleFeeBase(std::uint64_t fee, Fees const& fees)
// NIKB TODO: Once we get C++17, we can replace lowestTerms
// with this:
//
// template <class T1, class T2,
// class = std::enable_if_t<
// std::is_integral_v<T1> &&
// std::is_integral_v<T2>>
// >
// void lowestTerms(T1& a, T2& b)
// {
// if (auto const gcd = std::gcd(a, b))
// {
// a /= gcd;
// b /= gcd;
// }
// }
template <class T1, class T2,
class = std::enable_if_t <
std::is_integral<T1>::value &&
std::is_unsigned<T1>::value &&
sizeof(T1) <= sizeof(std::uint64_t) >,
class = std::enable_if_t <
std::is_integral<T2>::value &&
std::is_unsigned<T2>::value &&
sizeof(T2) <= sizeof(std::uint64_t) >
>
void lowestTerms(T1& a, T2& b)
{
return mulDivThrow (fee, fees.base, fees.units);
if (a == 0 && b == 0)
return;
std::uint64_t x = a, y = b;
while (y != 0)
{
auto t = x % y;
x = y;
y = t;
}
a /= x;
b /= x;
}
// Scale using load as well as base rate