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

Source/platform/DecimalTest.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 224 matching lines @@
     EXPECT_EQ(Decimal(0), encode(1, -10, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(11, -1, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(13, -1, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(15, -1, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(19, -1, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(151, -2, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(101, -2, Negative).ceil());
     EXPECT_EQ(Decimal(0), encode(199, -3, Negative).ceil());
     EXPECT_EQ(Decimal(-1), encode(199, -2, Negative).ceil());
     EXPECT_EQ(Decimal(-2), encode(209, -2, Negative).ceil());
+    EXPECT_EQ(Decimal(1), encode(UINT64_C(123456789012345678), -18, Positive).ceil());
 }
 
 TEST_F(DecimalTest, CeilingBigExponent)
 {
     EXPECT_EQ(encode(1, 1000, Positive), encode(1, 1000, Positive).ceil());
     EXPECT_EQ(encode(1, 1000, Negative), encode(1, 1000, Negative).ceil());
 }
 
 TEST_F(DecimalTest, CeilingSmallExponent)
 {
@@ skipping 231 matching lines @@
     EXPECT_DECIMAL_ENCODED_DATA_EQ(UINT64_C(100000000000000000), 0, Negative, encode(UINT64_C(100000000000000000), 0, Negative));
 }
 
 TEST_F(DecimalTest, Division)
 {
     EXPECT_EQ(encode(0, 0, Positive), Decimal(0) / Decimal(1));
     EXPECT_EQ(encode(2, 0, Negative), Decimal(2) / Decimal(-1));
     EXPECT_EQ(encode(5, -1, Negative), Decimal(-1) / Decimal(2));
     EXPECT_EQ(encode(99, 0, Positive), Decimal(99) / Decimal(1));
     EXPECT_EQ(Decimal(1), Decimal(-50) / Decimal(-50));
-    EXPECT_EQ(encode(UINT64_C(33333333333333333), -17, Positive), Decimal(1) / Decimal(3));
+    EXPECT_EQ(encode(UINT64_C(333333333333333333), -18, Positive), Decimal(1) / Decimal(3));
     EXPECT_EQ(encode(UINT64_C(12345678901234), -1, Positive), encode(UINT64_C(12345678901234), 0, Positive) / Decimal(10));
+    EXPECT_EQ(encode(UINT64_C(500005000050000500), -18, Positive), Decimal(50000) / Decimal(99999));
 }
 
 TEST_F(DecimalTest, DivisionBigExponent)
 {
     EXPECT_EQ(encode(1, 1022, Positive), encode(1, 1022, Positive) / encode(1, 0, Positive));
     EXPECT_EQ(encode(1, 0, Positive), encode(1, 1022, Positive) / encode(1, 1022, Positive));
     EXPECT_EQ(Decimal::infinity(Positive), encode(1, 1022, Positive) / encode(1, -1000, Positive));
 }
 
 TEST_F(DecimalTest, DivisionSmallExponent)
@@ skipping 606 matching lines @@
     EXPECT_DECIMAL_STREQ("0.001", encode(UINT64_C(99999999999999999), -20, Positive));
     EXPECT_DECIMAL_STREQ("1e-83", encode(UINT64_C(99999999999999999), -100, Positive));
 }
 
 TEST_F(DecimalTest, ToStringSpecialValues)
 {
     EXPECT_DECIMAL_STREQ("Infinity", Decimal::infinity(Positive));
     EXPECT_DECIMAL_STREQ("-Infinity", Decimal::infinity(Negative));
     EXPECT_DECIMAL_STREQ("NaN", Decimal::nan());
 }