base/cxx17_backports_unittest.cc

// Copyright 2021 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 "base/cxx17_backports.h"

#include <array>
#include <memory>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

#include "base/test/gtest_util.h"
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {
namespace {

struct OneType {
  int some_int;
};

bool operator<(const OneType& lhs, const OneType& rhs) {
  return lhs.some_int < rhs.some_int;
}

bool operator==(const OneType& lhs, const OneType& rhs) {
  return lhs.some_int == rhs.some_int;
}

struct AnotherType {
  int some_other_int;
};

bool operator==(const AnotherType& lhs, const AnotherType& rhs) {
  return lhs.some_other_int == rhs.some_other_int;
}

TEST(Cxx17BackportTest, Clamp) {
  EXPECT_EQ(0, base::clamp(-5, 0, 10));
  EXPECT_EQ(0, base::clamp(0, 0, 10));
  EXPECT_EQ(3, base::clamp(3, 0, 10));
  EXPECT_EQ(10, base::clamp(10, 0, 10));
  EXPECT_EQ(10, base::clamp(15, 0, 10));

  EXPECT_EQ(0.0, base::clamp(-5.0, 0.0, 10.0));
  EXPECT_EQ(0.0, base::clamp(0.0, 0.0, 10.0));
  EXPECT_EQ(3.0, base::clamp(3.0, 0.0, 10.0));
  EXPECT_EQ(10.0, base::clamp(10.0, 0.0, 10.0));
  EXPECT_EQ(10.0, base::clamp(15.0, 0.0, 10.0));

  EXPECT_EQ(0, base::clamp(-5, 0, 0));
  EXPECT_EQ(0, base::clamp(0, 0, 0));
  EXPECT_EQ(0, base::clamp(3, 0, 0));

  OneType one_type_neg5{-5};
  OneType one_type_0{0};
  OneType one_type_3{3};
  OneType one_type_10{10};
  OneType one_type_15{15};

  EXPECT_EQ(one_type_0, base::clamp(one_type_neg5, one_type_0, one_type_10));
  EXPECT_EQ(one_type_0, base::clamp(one_type_0, one_type_0, one_type_10));
  EXPECT_EQ(one_type_3, base::clamp(one_type_3, one_type_0, one_type_10));
  EXPECT_EQ(one_type_10, base::clamp(one_type_10, one_type_0, one_type_10));
  EXPECT_EQ(one_type_10, base::clamp(one_type_15, one_type_0, one_type_10));

  AnotherType another_type_neg5{-5};
  AnotherType another_type_0{0};
  AnotherType another_type_3{3};
  AnotherType another_type_10{10};
  AnotherType another_type_15{15};

  auto compare_another_type = [](const auto& lhs, const auto& rhs) {
    return lhs.some_other_int < rhs.some_other_int;
  };

  EXPECT_EQ(another_type_0, base::clamp(another_type_neg5, another_type_0,
                                        another_type_10, compare_another_type));
  EXPECT_EQ(another_type_0, base::clamp(another_type_0, another_type_0,
                                        another_type_10, compare_another_type));
  EXPECT_EQ(another_type_3, base::clamp(another_type_3, another_type_0,
                                        another_type_10, compare_another_type));
  EXPECT_EQ(another_type_10,
            base::clamp(another_type_10, another_type_0, another_type_10,
                        compare_another_type));
  EXPECT_EQ(another_type_10,
            base::clamp(another_type_15, another_type_0, another_type_10,
                        compare_another_type));

  EXPECT_CHECK_DEATH(base::clamp(3, 10, 0));
  EXPECT_CHECK_DEATH(base::clamp(3.0, 10.0, 0.0));
  EXPECT_CHECK_DEATH(base::clamp(one_type_3, one_type_10, one_type_0));
  EXPECT_CHECK_DEATH(base::clamp(another_type_3, another_type_10,
                                 another_type_0, compare_another_type));
}

constexpr int Subtract(int a, int b) {
  return a - b;
}

int SubtractUnique(std::unique_ptr<int> a, std::unique_ptr<int> b) {
  return *a - *b;
}

TEST(Cxx17BackportTest, Apply) {
  // Function
  constexpr std::tuple<int, int> tuple1(3, 2);
  static_assert(base::apply(&Subtract, tuple1) == 1,
                "base::apply() can invoke functions as constexpr");

  // Function with move-only types
  std::tuple<std::unique_ptr<int>, std::unique_ptr<int>> tuple2(
      std::make_unique<int>(3), std::make_unique<int>(2));
  EXPECT_EQ(1, base::apply(&SubtractUnique, std::move(tuple2)));

  // Lambda
  const auto subtract_lambda = [](int a, int b) { return a - b; };
  EXPECT_EQ(1, base::apply(subtract_lambda, tuple1));

  // Member function
  class Foo {
   public:
    constexpr Foo(int a) : a_(a) {}

    constexpr int Bar(int b) const { return a_ - b; }

   private:
    int a_;
  };
  static constexpr Foo f(3);
  constexpr std::tuple<const Foo*, int> tuple3(&f, 2);
  static_assert(base::apply(&Foo::Bar, tuple3) == 1,
                "base::apply() can invoke member functions as constexpr");
}

}  // namespace
}  // namespace base