Avoid uint64_t overflow in Decimal::operator/() and fix Decimal::ceil()

Source/platform/Decimal.cpp

Index: Source/platform/Decimal.cpp
diff --git a/Source/platform/Decimal.cpp b/Source/platform/Decimal.cpp
index 35b5a8aaf4e6ccb7b197748fb647de2968e950fc..97013153dc5eabf11bde42d383cb1bb0b03d6eda 100644
--- a/Source/platform/Decimal.cpp
+++ b/Source/platform/Decimal.cpp
@@ -488,13 +488,18 @@ Decimal Decimal::operator/(const Decimal& rhs) const
     uint64_t remainder = lhs.m_data.coefficient();
     const uint64_t divisor = rhs.m_data.coefficient();
     uint64_t result = 0;
-    while (result < MaxCoefficient / 100) {
-        while (remainder < divisor) {
+    for (;;) {
+        while (remainder < divisor && result < MaxCoefficient / 10) {
             remainder *= 10;
             result *= 10;
             --resultExponent;
         }
-        result += remainder / divisor;
+        if (remainder < divisor)
+            break;
+        uint64_t quotient = remainder / divisor;
+        if (result > MaxCoefficient - quotient)
+            break;
+        result += quotient;
         remainder %= divisor;
         if (!remainder)
             break;
@@ -628,7 +633,7 @@ Decimal Decimal::ceil() const
     uint64_t result = m_data.coefficient();
     const int numberOfDigits = countDigits(result);
     const int numberOfDropDigits = -exponent();
-    if (numberOfDigits < numberOfDropDigits)
+    if (numberOfDigits <= numberOfDropDigits)
         return isPositive() ? Decimal(1) : zero(Positive);
 
     result = scaleDown(result, numberOfDropDigits);