Fix Decimal.floor() + Decimal.ceiling() for most non-integral values.

Source/platform/Decimal.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 594 matching lines @@
         }
     }
 
     AlignedOperands alignedOperands;
     alignedOperands.exponent = exponent;
     alignedOperands.lhsCoefficient = lhsCoefficient;
     alignedOperands.rhsCoefficient = rhsCoefficient;
     return alignedOperands;
 }
 
+static bool isMultiplePowersOfTen(uint64_t coefficient, int n)
+{
+    return !coefficient || !(coefficient % scaleUp(1, n));
+}
+
 // Round toward positive infinity.
 // Note: Mac ports defines ceil(x) as wtf_ceil(x), so we can't use name "ceil" here.
 Decimal Decimal::ceiling() const
 {
     if (isSpecial())
         return *this;
 
     if (exponent() >= 0)
         return *this;
 
     uint64_t result = m_data.coefficient();
     const int numberOfDigits = countDigits(result);
     const int numberOfDropDigits = -exponent();
     if (numberOfDigits < numberOfDropDigits)
         return isPositive() ? Decimal(1) : zero(Positive);
 
-    result = scaleDown(result, numberOfDropDigits - 1);
-    if (sign() == Positive && result % 10 > 0)
-        result += 10;
-    result /= 10;
+    result = scaleDown(result, numberOfDropDigits);
+    if (isPositive() && !isMultiplePowersOfTen(m_data.coefficient(), numberOfDropDigits))
+        ++result;
     return Decimal(sign(), 0, result);
 }
 
 Decimal Decimal::compareTo(const Decimal& rhs) const
 {
     const Decimal result(*this - rhs);
     switch (result.m_data.formatClass()) {
     case EncodedData::ClassInfinity:
         return result.isNegative() ? Decimal(-1) : Decimal(1);
 
@@ skipping 18 matching lines @@
 
     if (exponent() >= 0)
         return *this;
 
     uint64_t result = m_data.coefficient();
     const int numberOfDigits = countDigits(result);
     const int numberOfDropDigits = -exponent();
     if (numberOfDigits < numberOfDropDigits)
         return isPositive() ? zero(Positive) : Decimal(-1);
 
-    result = scaleDown(result, numberOfDropDigits - 1);
-    if (isNegative() && result % 10 > 0)
-        result += 10;
-    result /= 10;
+    result = scaleDown(result, numberOfDropDigits);
+    if (isNegative() && !isMultiplePowersOfTen(m_data.coefficient(), numberOfDropDigits))
+        ++result;
     return Decimal(sign(), 0, result);
 }
 
 Decimal Decimal::fromDouble(double doubleValue)
 {
     if (std::isfinite(doubleValue))
         return fromString(String::numberToStringECMAScript(doubleValue));
 
     if (std::isinf(doubleValue))
         return infinity(doubleValue < 0 ? Negative : Positive);
@@ skipping 338 matching lines @@
     }
     return builder.toString();
 }
 
 Decimal Decimal::zero(Sign sign)
 {
     return Decimal(EncodedData(sign, EncodedData::ClassZero));
 }
 
 } // namespace WebCore