// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Tests for pointer utilities.

#include "absl/memory/memory.h"

#include <sys/types.h>

#include <cstddef>
#include <memory>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>

#include "gmock/gmock.h"
#include "gtest/gtest.h"

namespace {

using ::testing::ElementsAre;
using ::testing::Return;

// This class creates observable behavior to verify that a destructor has
// been called, via the instance_count variable.
class DestructorVerifier {
 public:
  DestructorVerifier() { ++instance_count_; }
  DestructorVerifier(const DestructorVerifier&) = delete;
  DestructorVerifier& operator=(const DestructorVerifier&) = delete;
  ~DestructorVerifier() { --instance_count_; }

  // The number of instances of this class currently active.
  static int instance_count() { return instance_count_; }

 private:
  // The number of instances of this class currently active.
  static int instance_count_;
};

int DestructorVerifier::instance_count_ = 0;

TEST(WrapUniqueTest, WrapUnique) {
  // Test that the unique_ptr is constructed properly by verifying that the
  // destructor for its payload gets called at the proper time.
  {
    auto dv = new DestructorVerifier;
    EXPECT_EQ(1, DestructorVerifier::instance_count());
    std::unique_ptr<DestructorVerifier> ptr = absl::WrapUnique(dv);
    EXPECT_EQ(1, DestructorVerifier::instance_count());
  }
  EXPECT_EQ(0, DestructorVerifier::instance_count());
}

TEST(MakeUniqueForOverwriteTest, Basic) {
  std::unique_ptr<int> p = absl::make_unique_for_overwrite<int>();
  p = absl::make_unique_for_overwrite<int>();
}

// The initialization tests needs to suppress dead-store elimination, otherwise
// memset is optimized away, and lifetime is assumed begin after new, triggering
// uninitalized variable warnings. Various tricks to prevent memset from being
// optimized away still result in uninitialized variable warnings.  Once we move
// to a C++20 floor we can delegate to std::make_unique_for_overwrite and avoid
// testing absl::make_unique_for_overwrite.
// https://github.com/gcc-mirror/gcc/blob/be1da01067c898a3e3979bfb1edd05f115ab2e3e/libstdc%2B%2B-v3/testsuite/20_util/unique_ptr/creation/for_overwrite.cc#L1
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC push_options
#pragma GCC optimize("O0")
#endif

// InitializationVerifier fills in a pattern when allocated so we can
// distinguish between its default and value initialized states (without
// accessing truly uninitialized memory).
struct InitializationVerifier {
  static constexpr int kDefaultScalar = 0x43;
  static constexpr int kDefaultArray = 0x4B;

  static void* operator new(size_t n) {
    void* ret = ::operator new(n);
    memset(ret, kDefaultScalar, n);
    return ret;
  }

  static void* operator new[](size_t n) {
    void* ret = ::operator new[](n);
    memset(ret, kDefaultArray, n);
    return ret;
  }

  int a;
  int b;
};

TEST(Initialization, MakeUniqueForOverwrite) {
  auto p = absl::make_unique_for_overwrite<InitializationVerifier>();

  int pattern;
  memset(&pattern, InitializationVerifier::kDefaultScalar, sizeof(pattern));

  EXPECT_EQ(pattern, p->a);
  EXPECT_EQ(pattern, p->b);
}

TEST(Initialization, MakeUniqueForOverwriteArray) {
  auto p = absl::make_unique_for_overwrite<InitializationVerifier[]>(2);

  int pattern;
  memset(&pattern, InitializationVerifier::kDefaultArray, sizeof(pattern));

  EXPECT_EQ(pattern, p[0].a);
  EXPECT_EQ(pattern, p[0].b);
  EXPECT_EQ(pattern, p[1].a);
  EXPECT_EQ(pattern, p[1].b);
}

#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC pop_options
#endif

struct ArrayWatch {
  void* operator new[](size_t n) {
    allocs().push_back(n);
    return ::operator new[](n);
  }
  void operator delete[](void* p) { return ::operator delete[](p); }
  static std::vector<size_t>& allocs() {
    static auto& v = *new std::vector<size_t>;
    return v;
  }
};

TEST(MakeUniqueForOverwriteTest, Array) {
  // Ensure state is clean before we start so that these tests
  // are order-agnostic.
  ArrayWatch::allocs().clear();

  auto p = absl::make_unique_for_overwrite<ArrayWatch[]>(5);
  static_assert(std::is_same_v<decltype(p), std::unique_ptr<ArrayWatch[]>>,
                "unexpected return type");
  EXPECT_THAT(ArrayWatch::allocs(), ElementsAre(5 * sizeof(ArrayWatch)));
}

TEST(RawPtrTest, RawPointer) {
  int i = 5;
  EXPECT_EQ(&i, absl::RawPtr(&i));
}

TEST(RawPtrTest, SmartPointer) {
  int* o = new int(5);
  std::unique_ptr<int> p(o);
  EXPECT_EQ(o, absl::RawPtr(p));
}

class IntPointerNonConstDeref {
 public:
  explicit IntPointerNonConstDeref(int* p) : p_(p) {}
  friend bool operator!=(const IntPointerNonConstDeref& a, std::nullptr_t) {
    return a.p_ != nullptr;
  }
  int& operator*() { return *p_; }

 private:
  std::unique_ptr<int> p_;
};

TEST(RawPtrTest, SmartPointerNonConstDereference) {
  int* o = new int(5);
  IntPointerNonConstDeref p(o);
  EXPECT_EQ(o, absl::RawPtr(p));
}

TEST(RawPtrTest, NullValuedRawPointer) {
  int* p = nullptr;
  EXPECT_EQ(nullptr, absl::RawPtr(p));
}

TEST(RawPtrTest, NullValuedSmartPointer) {
  std::unique_ptr<int> p;
  EXPECT_EQ(nullptr, absl::RawPtr(p));
}

TEST(RawPtrTest, Nullptr) {
  auto p = absl::RawPtr(nullptr);
  EXPECT_TRUE((std::is_same_v<std::nullptr_t, decltype(p)>));
  EXPECT_EQ(nullptr, p);
}

TEST(RawPtrTest, Null) {
  auto p = absl::RawPtr(nullptr);
  EXPECT_TRUE((std::is_same_v<std::nullptr_t, decltype(p)>));
  EXPECT_EQ(nullptr, p);
}

TEST(RawPtrTest, Zero) {
  auto p = absl::RawPtr(nullptr);
  EXPECT_TRUE((std::is_same_v<std::nullptr_t, decltype(p)>));
  EXPECT_EQ(nullptr, p);
}

TEST(ShareUniquePtrTest, Share) {
  auto up = std::make_unique<int>();
  int* rp = up.get();
  auto sp = absl::ShareUniquePtr(std::move(up));
  EXPECT_EQ(sp.get(), rp);
}

TEST(ShareUniquePtrTest, ShareNull) {
  struct NeverDie {
    using pointer = void*;
    void operator()(pointer) {
      ASSERT_TRUE(false) << "Deleter should not have been called.";
    }
  };

  std::unique_ptr<void, NeverDie> up;
  auto sp = absl::ShareUniquePtr(std::move(up));
}

TEST(WeakenPtrTest, Weak) {
  auto sp = std::make_shared<int>();
  auto wp = absl::WeakenPtr(sp);
  EXPECT_EQ(sp.get(), wp.lock().get());
  sp.reset();
  EXPECT_TRUE(wp.expired());
}

// Should not compile.
/*
TEST(RawPtrTest, NotAPointer) {
  absl::RawPtr(1.5);
}
*/

TEST(AllocatorNoThrowTest, DefaultAllocator) {
#if defined(ABSL_ALLOCATOR_NOTHROW) && ABSL_ALLOCATOR_NOTHROW
  EXPECT_TRUE(absl::default_allocator_is_nothrow::value);
#else
  EXPECT_FALSE(absl::default_allocator_is_nothrow::value);
#endif
}

TEST(AllocatorNoThrowTest, StdAllocator) {
#if defined(ABSL_ALLOCATOR_NOTHROW) && ABSL_ALLOCATOR_NOTHROW
  EXPECT_TRUE(absl::allocator_is_nothrow<std::allocator<int>>::value);
#else
  EXPECT_FALSE(absl::allocator_is_nothrow<std::allocator<int>>::value);
#endif
}

TEST(AllocatorNoThrowTest, CustomAllocator) {
  struct NoThrowAllocator {
    using is_nothrow = std::true_type;
  };
  struct CanThrowAllocator {
    using is_nothrow = std::false_type;
  };
  struct UnspecifiedAllocator {};
  EXPECT_TRUE(absl::allocator_is_nothrow<NoThrowAllocator>::value);
  EXPECT_FALSE(absl::allocator_is_nothrow<CanThrowAllocator>::value);
  EXPECT_FALSE(absl::allocator_is_nothrow<UnspecifiedAllocator>::value);
}

}  // namespace