Move SaturatedArithmetic from Blink to base

base/numerics/saturated_arithmetic_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <limits>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/numerics/saturated_arithmetic.h"
+#include "build/build_config.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+TEST(SaturatedArithmeticTest, Addition) {
+  int int_max = std::numeric_limits<int>::max();
+  int int_min = std::numeric_limits<int>::min();
+
+  EXPECT_EQ(0, SaturatedAddition(0, 0));
+  EXPECT_EQ(1, SaturatedAddition(0, 1));
+  EXPECT_EQ(100, SaturatedAddition(0, 100));
+  EXPECT_EQ(150, SaturatedAddition(100, 50));
+
+  EXPECT_EQ(-1, SaturatedAddition(0, -1));
+  EXPECT_EQ(0, SaturatedAddition(1, -1));
+  EXPECT_EQ(50, SaturatedAddition(100, -50));
+  EXPECT_EQ(-50, SaturatedAddition(50, -100));
+
+  EXPECT_EQ(int_max - 1, SaturatedAddition(int_max - 1, 0));
+  EXPECT_EQ(int_max, SaturatedAddition(int_max - 1, 1));
+  EXPECT_EQ(int_max, SaturatedAddition(int_max - 1, 2));
+  EXPECT_EQ(int_max - 1, SaturatedAddition(0, int_max - 1));
+  EXPECT_EQ(int_max, SaturatedAddition(1, int_max - 1));
+  EXPECT_EQ(int_max, SaturatedAddition(2, int_max - 1));
+  EXPECT_EQ(int_max, SaturatedAddition(int_max - 1, int_max - 1));
+  EXPECT_EQ(int_max, SaturatedAddition(int_max, int_max));
+
+  EXPECT_EQ(int_min, SaturatedAddition(int_min, 0));
+  EXPECT_EQ(int_min + 1, SaturatedAddition(int_min + 1, 0));
+  EXPECT_EQ(int_min + 2, SaturatedAddition(int_min + 1, 1));
+  EXPECT_EQ(int_min + 3, SaturatedAddition(int_min + 1, 2));
+  EXPECT_EQ(int_min, SaturatedAddition(int_min + 1, -1));
+  EXPECT_EQ(int_min, SaturatedAddition(int_min + 1, -2));
+  EXPECT_EQ(int_min + 1, SaturatedAddition(0, int_min + 1));
+  EXPECT_EQ(int_min, SaturatedAddition(-1, int_min + 1));
+  EXPECT_EQ(int_min, SaturatedAddition(-2, int_min + 1));
+
+  EXPECT_EQ(int_max / 2 + 10000, SaturatedAddition(int_max / 2, 10000));
+  EXPECT_EQ(int_max, SaturatedAddition(int_max / 2 + 1, int_max / 2 + 1));
+  EXPECT_EQ(-1, SaturatedAddition(int_min, int_max));
+}
+
+TEST(SaturatedArithmeticTest, Subtraction) {
+  int int_max = std::numeric_limits<int>::max();
+  int int_min = std::numeric_limits<int>::min();
+
+  EXPECT_EQ(0, SaturatedSubtraction(0, 0));
+  EXPECT_EQ(-1, SaturatedSubtraction(0, 1));
+  EXPECT_EQ(-100, SaturatedSubtraction(0, 100));
+  EXPECT_EQ(50, SaturatedSubtraction(100, 50));
+
+  EXPECT_EQ(1, SaturatedSubtraction(0, -1));
+  EXPECT_EQ(2, SaturatedSubtraction(1, -1));
+  EXPECT_EQ(150, SaturatedSubtraction(100, -50));
+  EXPECT_EQ(150, SaturatedSubtraction(50, -100));
+
+  EXPECT_EQ(int_max, SaturatedSubtraction(int_max, 0));
+  EXPECT_EQ(int_max - 1, SaturatedSubtraction(int_max, 1));
+  EXPECT_EQ(int_max - 1, SaturatedSubtraction(int_max - 1, 0));
+  EXPECT_EQ(int_max, SaturatedSubtraction(int_max - 1, -1));
+  EXPECT_EQ(int_max, SaturatedSubtraction(int_max - 1, -2));
+  EXPECT_EQ(-int_max + 1, SaturatedSubtraction(0, int_max - 1));
+  EXPECT_EQ(-int_max, SaturatedSubtraction(-1, int_max - 1));
+  EXPECT_EQ(-int_max - 1, SaturatedSubtraction(-2, int_max - 1));
+  EXPECT_EQ(-int_max - 1, SaturatedSubtraction(-3, int_max - 1));
+
+  EXPECT_EQ(int_min, SaturatedSubtraction(int_min, 0));
+  EXPECT_EQ(int_min + 1, SaturatedSubtraction(int_min + 1, 0));
+  EXPECT_EQ(int_min, SaturatedSubtraction(int_min + 1, 1));
+  EXPECT_EQ(int_min, SaturatedSubtraction(int_min + 1, 2));
+
+  EXPECT_EQ(0, SaturatedSubtraction(int_min, int_min));
+  EXPECT_EQ(0, SaturatedSubtraction(int_max, int_max));
+  EXPECT_EQ(int_max, SaturatedSubtraction(int_max, int_min));
+}
+
+TEST(SaturatedArithmeticTest, SetSigned) {
+  int int_max = std::numeric_limits<int>::max();
+  int int_min = std::numeric_limits<int>::min();
+
+  const int kFractionBits = 6;
+  const int kIntMaxForLayoutUnit = int_max >> kFractionBits;
+  const int kIntMinForLayoutUnit = int_min >> kFractionBits;
+
+  EXPECT_EQ(0, SaturatedSet<kFractionBits>(0));
+
+  // Internally the max number we can represent (without saturating)
+  // is all the (non-sign) bits set except for the bottom n fraction bits
+  const int max_internal_representation = int_max ^ ((1 << kFractionBits) - 1);
+  EXPECT_EQ(max_internal_representation,
+            SaturatedSet<kFractionBits>(kIntMaxForLayoutUnit));
+
+  EXPECT_EQ(GetMaxSaturatedSetResultForTesting(kFractionBits),
+            SaturatedSet<kFractionBits>(kIntMaxForLayoutUnit + 100));
+
+  EXPECT_EQ((kIntMaxForLayoutUnit - 100) << kFractionBits,
+            SaturatedSet<kFractionBits>(kIntMaxForLayoutUnit - 100));
+
+  EXPECT_EQ(GetMinSaturatedSetResultForTesting(kFractionBits),
+            SaturatedSet<kFractionBits>(kIntMinForLayoutUnit));
+
+  EXPECT_EQ(GetMinSaturatedSetResultForTesting(kFractionBits),
+            SaturatedSet<kFractionBits>(kIntMinForLayoutUnit - 100));
+
+  // Shifting negative numbers left has undefined behavior, so use
+  // multiplication instead of direct shifting here.
+  EXPECT_EQ((kIntMinForLayoutUnit + 100) * (1 << kFractionBits),
+            SaturatedSet<kFractionBits>(kIntMinForLayoutUnit + 100));
+}
+
+TEST(SaturatedArithmeticTest, SetUnsigned) {
+  int int_max = std::numeric_limits<int>::max();
+
+  const int kFractionBits = 6;
+  const int kIntMaxForLayoutUnit = int_max >> kFractionBits;
+
+  EXPECT_EQ(0, SaturatedSet<kFractionBits>((unsigned)0));
+
+  EXPECT_EQ(GetMaxSaturatedSetResultForTesting(kFractionBits),
+            SaturatedSet<kFractionBits>((unsigned)kIntMaxForLayoutUnit));
+
+  const unsigned kOverflowed = kIntMaxForLayoutUnit + 100;
+  EXPECT_EQ(GetMaxSaturatedSetResultForTesting(kFractionBits),
+            SaturatedSet<kFractionBits>(kOverflowed));
+
+  const unsigned kNotOverflowed = kIntMaxForLayoutUnit - 100;
+  EXPECT_EQ((kIntMaxForLayoutUnit - 100) << kFractionBits,
+            SaturatedSet<kFractionBits>(kNotOverflowed));
+}
+
+}  // namespace base