third_party/WebKit/Source/wtf/SaturatedArithmeticTest.cpp

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#include "wtf/SaturatedArithmetic.h"

#include "testing/gtest/include/gtest/gtest.h"
#include <limits.h>

namespace WTF {

TEST(SaturatedArithmeticTest, Addition) {
  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) {
  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) {
  const int kFractionBits = 6;
  const int intMaxForLayoutUnit = INT_MAX >> kFractionBits;
  const int intMinForLayoutUnit = 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 maxInternalRepresentation = INT_MAX ^ ((1 << kFractionBits) - 1);
  EXPECT_EQ(maxInternalRepresentation,
            saturatedSet<kFractionBits>(intMaxForLayoutUnit));

  EXPECT_EQ(getMaxSaturatedSetResultForTesting(kFractionBits),
            saturatedSet<kFractionBits>(intMaxForLayoutUnit + 100));

  EXPECT_EQ((intMaxForLayoutUnit - 100) << kFractionBits,
            saturatedSet<kFractionBits>(intMaxForLayoutUnit - 100));

  EXPECT_EQ(getMinSaturatedSetResultForTesting(kFractionBits),
            saturatedSet<kFractionBits>(intMinForLayoutUnit));

  EXPECT_EQ(getMinSaturatedSetResultForTesting(kFractionBits),
            saturatedSet<kFractionBits>(intMinForLayoutUnit - 100));

  // Shifting negative numbers left has undefined behavior, so use
  // multiplication instead of direct shifting here.
  EXPECT_EQ((intMinForLayoutUnit + 100) * (1 << kFractionBits),
            saturatedSet<kFractionBits>(intMinForLayoutUnit + 100));
}

TEST(SaturatedArithmeticTest, SetUnsigned) {
  const int kFractionBits = 6;
  const int intMaxForLayoutUnit = INT_MAX >> kFractionBits;

  EXPECT_EQ(0, saturatedSet<kFractionBits>((unsigned)0));

  EXPECT_EQ(getMaxSaturatedSetResultForTesting(kFractionBits),
            saturatedSet<kFractionBits>((unsigned)intMaxForLayoutUnit));

  const unsigned kOverflowed = intMaxForLayoutUnit + 100;
  EXPECT_EQ(getMaxSaturatedSetResultForTesting(kFractionBits),
            saturatedSet<kFractionBits>(kOverflowed));

  const unsigned kNotOverflowed = intMaxForLayoutUnit - 100;
  EXPECT_EQ((intMaxForLayoutUnit - 100) << kFractionBits,
            saturatedSet<kFractionBits>(kNotOverflowed));
}

}  // namespace WTF