mulDiv returns 0 if numerator is 0 and denominator isn't:

* Otherwise overflow checks result in divide by 0.
* If denominator is 0, let the divide by 0 exception throw.
* Move mulDiv out of STAmount

src/ripple/protocol/STAmount.h

@@ -418,35 +418,6 @@ inline bool isXRP(STAmount const& amount)
     return isXRP (amount.issue().currency);
 }
 
-/**
-    A utility function to compute (value)*(mul)/(div) while avoiding
-    overflow but keeping precision.
-*/
-std::uint64_t
-mulDiv(std::uint64_t value, std::uint64_t mul, std::uint64_t div);
-
-/**
-    A utility function to compute (value)*(mul)/(div) while avoiding
-    overflow but keeping precision. Will return the max uint64_t
-    value if mulDiv would overflow anyway.
-*/
-std::uint64_t
-mulDivNoThrow(std::uint64_t value, std::uint64_t mul, std::uint64_t div);
-
-template <class T1, class T2>
-void lowestTerms(T1& a,  T2& b)
-{
-    std::uint64_t x = a, y = b;
-    while (y != 0)
-    {
-        auto t = x % y;
-        x = y;
-        y = t;
-    }
-    a /= x;
-    b /= x;
-}
-
 } // ripple
 
 #endif

src/ripple/protocol/impl/STAmount.cpp

@@ -1275,40 +1275,6 @@ divRound (STAmount const& num, STAmount const& den,
     return result;
 }
 
-// compute (value)*(mul)/(div) - avoid overflow but keep precision
-std::uint64_t
-mulDiv(std::uint64_t value, std::uint64_t mul, std::uint64_t div)
-{
-    lowestTerms(value, div);
-    lowestTerms(mul, div);
-
-    if (value < mul)
-        std::swap(value, mul);
-    const auto max = std::numeric_limits<std::uint64_t>::max();
-    if (value > max / mul)
-    {
-        value /= div;
-        if (value > max / mul)
-            Throw<std::overflow_error> ("mulDiv");
-        return value * mul;
-    }
-    return value * mul / div;
-}
-
-// compute (value)*(mul)/(div) - avoid overflow but keep precision
-std::uint64_t
-mulDivNoThrow(std::uint64_t value, std::uint64_t mul, std::uint64_t div)
-{
-    try
-    {
-        return mulDiv(value, mul, div);
-    }
-    catch (std::overflow_error)
-    {
-        return std::numeric_limits<std::uint64_t>::max();
-    }
-}
-
 NetClock::time_point
 STAmountCalcSwitchovers::enableUnderflowFixCloseTime ()
 {