Clean-ups and tweaks

include/xrpl/basics/Number.h

@@ -632,7 +632,7 @@ private:
 
     /** Breaks down the number into components, potentially de-normalizing it.
      *
-     * Ensures that the mantissa always has range_.log digits.
+     * Ensures that the mantissa always has range_.log + 1 digits.
      *
      */
     template <detail::UnsignedMantissa Rep = internalrep>
@@ -641,7 +641,7 @@ private:
 
     /** Breaks down the number into components, potentially de-normalizing it.
      *
-     * Ensures that the mantissa always has range_.log digits.
+     * Ensures that the mantissa always has range_.log + 1 digits.
      *
      */
     template <detail::UnsignedMantissa Rep = internalrep>

src/libxrpl/basics/Number.cpp

@@ -293,7 +293,8 @@ Number::Guard::doRound(rep& drops, std::string_view location)
     auto r = round();
     if (r == 1 || (r == 0 && (drops & 1) == 1))
     {
-        if (drops >= maxMantissa())
+        auto const& range = range_.get();
+        if (drops >= range.max)
         {
             static_assert(sizeof(internalrep) == sizeof(rep));
             // This should be impossible, because it's impossible to represent
@@ -1120,7 +1121,7 @@ Number::root(MantissaRange const& range, Number f, unsigned d)
 
         // Scale f into the range (0, 1) such that the scale change (e) is a
         // multiple of the root (d)
-        auto e = exponent + Number::mantissaLog() + 1;
+        auto e = exponent + range.log + 1;
         auto const di = static_cast<int>(d);
         auto ex = [e = e, di = di]()  // Euclidean remainder of e/d
         {
@@ -1213,7 +1214,7 @@ root2(Number f)
 
         // Scale f into the range (0, 1) such that f's exponent is a
         // multiple of d
-        auto e = exponent + Number::mantissaLog() + 1;
+        auto e = exponent + range.log + 1;
         if (e % 2 != 0)
             ++e;
         f = f.shiftExponent(-e);  // f /= 10^e;

src/test/basics/Number_test.cpp

@@ -228,6 +228,25 @@ public:
                     // result will overflow. With addition using uint128_t,
                     // there's no problem. After normalizing, the resulting
                     // mantissa ends up less than largestMantissa.
+                    Number{
+                        false,
+                        Number::largestMantissa,
+                        0,
+                        Number::normalized{}},
+                    Number{
+                        false,
+                        Number::largestMantissa,
+                        0,
+                        Number::normalized{}},
+                    Number{
+                        false,
+                        Number::largestMantissa * 2,
+                        0,
+                        Number::normalized{}},
+                },
+                {
+                    // These mantissas round down, so adding them together won't
+                    // have any consequences.
                     Number{
                         false,
                         9'999'999'999'999'999'990ULL,
@@ -604,7 +623,6 @@ public:
                          Number::normalized{}},
                      __LINE__},
                     // Maximum actual mantissa range - same as int64
-                    // 99'999'999'999'999'999'800'000'000'000'000'000'100
                     {Number{false, maxMantissa, 0, Number::normalized{}},
                      Number{false, maxMantissa, 0, Number::normalized{}},
                      Number{85'070'591'730'234'615'84, 19},