absl/hash/hash_test.cc

// Copyright 2018 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
//
//      http://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.

#include "absl/hash/hash.h"

#include <array>
#include <cstring>
#include <deque>
#include <forward_list>
#include <functional>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <random>
#include <set>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/container/flat_hash_set.h"
#include "absl/hash/hash_testing.h"
#include "absl/hash/internal/spy_hash_state.h"
#include "absl/meta/type_traits.h"
#include "absl/numeric/int128.h"

namespace {

using absl::Hash;
using absl::hash_internal::SpyHashState;

template <typename T>
class HashValueIntTest : public testing::Test {
};
TYPED_TEST_CASE_P(HashValueIntTest);

template <typename T>
SpyHashState SpyHash(const T& value) {
  return SpyHashState::combine(SpyHashState(), value);
}

// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
// detect it.
template <typename T>
using is_hashable = std::is_default_constructible<absl::Hash<T>>;

TYPED_TEST_P(HashValueIntTest, BasicUsage) {
  EXPECT_TRUE((is_hashable<TypeParam>::value));

  TypeParam n = 42;
  EXPECT_EQ(SpyHash(n), SpyHash(TypeParam{42}));
  EXPECT_NE(SpyHash(n), SpyHash(TypeParam{0}));
  EXPECT_NE(SpyHash(std::numeric_limits<TypeParam>::max()),
            SpyHash(std::numeric_limits<TypeParam>::min()));
}

TYPED_TEST_P(HashValueIntTest, FastPath) {
  // Test the fast-path to make sure the values are the same.
  TypeParam n = 42;
  EXPECT_EQ(absl::Hash<TypeParam>{}(n),
            absl::Hash<std::tuple<TypeParam>>{}(std::tuple<TypeParam>(n)));
}

REGISTER_TYPED_TEST_CASE_P(HashValueIntTest, BasicUsage, FastPath);
using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t, uint32_t,
                                uint64_t, size_t>;
INSTANTIATE_TYPED_TEST_CASE_P(My, HashValueIntTest, IntTypes);

template <typename T, typename = void>
struct IsHashCallble : std::false_type {};

template <typename T>
struct IsHashCallble<T, absl::void_t<decltype(std::declval<absl::Hash<T>>()(
                            std::declval<const T&>()))>> : std::true_type {};

template <typename T, typename = void>
struct IsAggregateInitializable : std::false_type {};

template <typename T>
struct IsAggregateInitializable<T, absl::void_t<decltype(T{})>>
    : std::true_type {};

TEST(IsHashableTest, ValidHash) {
  EXPECT_TRUE((is_hashable<int>::value));
  EXPECT_TRUE(std::is_default_constructible<absl::Hash<int>>::value);
  EXPECT_TRUE(std::is_copy_constructible<absl::Hash<int>>::value);
  EXPECT_TRUE(std::is_move_constructible<absl::Hash<int>>::value);
  EXPECT_TRUE(absl::is_copy_assignable<absl::Hash<int>>::value);
  EXPECT_TRUE(absl::is_move_assignable<absl::Hash<int>>::value);
  EXPECT_TRUE(IsHashCallble<int>::value);
  EXPECT_TRUE(IsAggregateInitializable<absl::Hash<int>>::value);
}
#if ABSL_HASH_INTERNAL_CAN_POISON_ && !defined(__APPLE__)
TEST(IsHashableTest, PoisonHash) {
  struct X {};
  EXPECT_FALSE((is_hashable<X>::value));
  EXPECT_FALSE(std::is_default_constructible<absl::Hash<X>>::value);
  EXPECT_FALSE(std::is_copy_constructible<absl::Hash<X>>::value);
  EXPECT_FALSE(std::is_move_constructible<absl::Hash<X>>::value);
  EXPECT_FALSE(absl::is_copy_assignable<absl::Hash<X>>::value);
  EXPECT_FALSE(absl::is_move_assignable<absl::Hash<X>>::value);
  EXPECT_FALSE(IsHashCallble<X>::value);
  EXPECT_FALSE(IsAggregateInitializable<absl::Hash<X>>::value);
}
#endif  // ABSL_HASH_INTERNAL_CAN_POISON_

// Hashable types
//
// These types exist simply to exercise various AbslHashValue behaviors, so
// they are named by what their AbslHashValue overload does.
struct NoOp {
  template <typename HashCode>
  friend HashCode AbslHashValue(HashCode h, NoOp n) {
    return std::move(h);
  }
};

struct EmptyCombine {
  template <typename HashCode>
  friend HashCode AbslHashValue(HashCode h, EmptyCombine e) {
    return HashCode::combine(std::move(h));
  }
};

template <typename Int>
struct CombineIterative {
  template <typename HashCode>
  friend HashCode AbslHashValue(HashCode h, CombineIterative c) {
    for (int i = 0; i < 5; ++i) {
      h = HashCode::combine(std::move(h), Int(i));
    }
    return h;
  }
};

template <typename Int>
struct CombineVariadic {
  template <typename HashCode>
  friend HashCode AbslHashValue(HashCode h, CombineVariadic c) {
    return HashCode::combine(std::move(h), Int(0), Int(1), Int(2), Int(3),
                             Int(4));
  }
};

using InvokeTag = absl::hash_internal::InvokeHashTag;
template <InvokeTag T>
using InvokeTagConstant = std::integral_constant<InvokeTag, T>;

template <InvokeTag... Tags>
struct MinTag;

template <InvokeTag a, InvokeTag b, InvokeTag... Tags>
struct MinTag<a, b, Tags...> : MinTag<(a < b ? a : b), Tags...> {};

template <InvokeTag a>
struct MinTag<a> : InvokeTagConstant<a> {};

template <InvokeTag... Tags>
struct CustomHashType {
  size_t value;
};

template <InvokeTag allowed, InvokeTag... tags>
struct EnableIfContained
    : std::enable_if<absl::disjunction<
          std::integral_constant<bool, allowed == tags>...>::value> {};

template <
    typename H, InvokeTag... Tags,
    typename = typename EnableIfContained<InvokeTag::kHashValue, Tags...>::type>
H AbslHashValue(H state, CustomHashType<Tags...> t) {
  static_assert(MinTag<Tags...>::value == InvokeTag::kHashValue, "");
  return H::combine(std::move(state),
                    t.value + static_cast<int>(InvokeTag::kHashValue));
}

}  // namespace

namespace absl {
inline namespace lts_2018_12_18 {
namespace hash_internal {
template <InvokeTag... Tags>
struct is_uniquely_represented<
    CustomHashType<Tags...>,
    typename EnableIfContained<InvokeTag::kUniquelyRepresented, Tags...>::type>
    : std::true_type {};
}  // namespace hash_internal
}  // inline namespace lts_2018_12_18
}  // namespace absl

#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE {
template <InvokeTag... Tags>
struct hash<CustomHashType<Tags...>> {
  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
                                     InvokeTag::kLegacyHash, TagsIn...>::type>
  size_t operator()(CustomHashType<TagsIn...> t) const {
    static_assert(MinTag<Tags...>::value == InvokeTag::kLegacyHash, "");
    return t.value + static_cast<int>(InvokeTag::kLegacyHash);
  }
};
}  // namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE
#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_

namespace std {
template <InvokeTag... Tags>  // NOLINT
struct hash<CustomHashType<Tags...>> {
  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
                                     InvokeTag::kStdHash, TagsIn...>::type>
  size_t operator()(CustomHashType<TagsIn...> t) const {
    static_assert(MinTag<Tags...>::value == InvokeTag::kStdHash, "");
    return t.value + static_cast<int>(InvokeTag::kStdHash);
  }
};
}  // namespace std

namespace {

template <typename... T>
void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>, T...) {
  using type = CustomHashType<T::value...>;
  SCOPED_TRACE(testing::PrintToString(std::vector<InvokeTag>{T::value...}));
  EXPECT_TRUE(is_hashable<type>());
  EXPECT_TRUE(is_hashable<const type>());
  EXPECT_TRUE(is_hashable<const type&>());

  const size_t offset = static_cast<int>(std::min({T::value...}));
  EXPECT_EQ(SpyHash(type{7}), SpyHash(size_t{7 + offset}));
}

void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>) {
#if ABSL_HASH_INTERNAL_CAN_POISON_
  // is_hashable is false if we don't support any of the hooks.
  using type = CustomHashType<>;
  EXPECT_FALSE(is_hashable<type>());
  EXPECT_FALSE(is_hashable<const type>());
  EXPECT_FALSE(is_hashable<const type&>());
#endif  // ABSL_HASH_INTERNAL_CAN_POISON_
}

template <InvokeTag Tag, typename... T>
void TestCustomHashType(InvokeTagConstant<Tag> tag, T... t) {
  constexpr auto next = static_cast<InvokeTag>(static_cast<int>(Tag) + 1);
  TestCustomHashType(InvokeTagConstant<next>(), tag, t...);
  TestCustomHashType(InvokeTagConstant<next>(), t...);
}

TEST(HashTest, CustomHashType) {
  TestCustomHashType(InvokeTagConstant<InvokeTag{}>());
}

TEST(HashTest, NoOpsAreEquivalent) {
  EXPECT_EQ(Hash<NoOp>()({}), Hash<NoOp>()({}));
  EXPECT_EQ(Hash<NoOp>()({}), Hash<EmptyCombine>()({}));
}

template <typename T>
class HashIntTest : public testing::Test {
};
TYPED_TEST_CASE_P(HashIntTest);

TYPED_TEST_P(HashIntTest, BasicUsage) {
  EXPECT_NE(Hash<NoOp>()({}), Hash<TypeParam>()(0));
  EXPECT_NE(Hash<NoOp>()({}),
            Hash<TypeParam>()(std::numeric_limits<TypeParam>::max()));
  if (std::numeric_limits<TypeParam>::min() != 0) {
    EXPECT_NE(Hash<NoOp>()({}),
              Hash<TypeParam>()(std::numeric_limits<TypeParam>::min()));
  }

  EXPECT_EQ(Hash<CombineIterative<TypeParam>>()({}),
            Hash<CombineVariadic<TypeParam>>()({}));
}

REGISTER_TYPED_TEST_CASE_P(HashIntTest, BasicUsage);
using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t, uint32_t,
                                uint64_t, size_t>;
INSTANTIATE_TYPED_TEST_CASE_P(My, HashIntTest, IntTypes);

struct StructWithPadding {
  char c;
  int i;

  template <typename H>
  friend H AbslHashValue(H hash_state, const StructWithPadding& s) {
    return H::combine(std::move(hash_state), s.c, s.i);
  }
};

static_assert(sizeof(StructWithPadding) > sizeof(char) + sizeof(int),
              "StructWithPadding doesn't have padding");
static_assert(std::is_standard_layout<StructWithPadding>::value, "");

// This check has to be disabled because libstdc++ doesn't support it.
// static_assert(std::is_trivially_constructible<StructWithPadding>::value, "");

template <typename T>
struct ArraySlice {
  T* begin;
  T* end;

  template <typename H>
  friend H AbslHashValue(H hash_state, const ArraySlice& slice) {
    for (auto t = slice.begin; t != slice.end; ++t) {
      hash_state = H::combine(std::move(hash_state), *t);
    }
    return hash_state;
  }
};

TEST(HashTest, HashNonUniquelyRepresentedType) {
  // Create equal StructWithPadding objects that are known to have non-equal
  // padding bytes.
  static const size_t kNumStructs = 10;
  unsigned char buffer1[kNumStructs * sizeof(StructWithPadding)];
  std::memset(buffer1, 0, sizeof(buffer1));
  auto* s1 = reinterpret_cast<StructWithPadding*>(buffer1);

  unsigned char buffer2[kNumStructs * sizeof(StructWithPadding)];
  std::memset(buffer2, 255, sizeof(buffer2));
  auto* s2 = reinterpret_cast<StructWithPadding*>(buffer2);
  for (int i = 0; i < kNumStructs; ++i) {
    SCOPED_TRACE(i);
    s1[i].c = s2[i].c = '0' + i;
    s1[i].i = s2[i].i = i;
    ASSERT_FALSE(memcmp(buffer1 + i * sizeof(StructWithPadding),
                        buffer2 + i * sizeof(StructWithPadding),
                        sizeof(StructWithPadding)) == 0)
        << "Bug in test code: objects do not have unequal"
        << " object representations";
  }

  EXPECT_EQ(Hash<StructWithPadding>()(s1[0]), Hash<StructWithPadding>()(s2[0]));
  EXPECT_EQ(Hash<ArraySlice<StructWithPadding>>()({s1, s1 + kNumStructs}),
            Hash<ArraySlice<StructWithPadding>>()({s2, s2 + kNumStructs}));
}

TEST(HashTest, StandardHashContainerUsage) {
  std::unordered_map<int, std::string, Hash<int>> map = {{0, "foo"}, { 42, "bar" }};

  EXPECT_NE(map.find(0), map.end());
  EXPECT_EQ(map.find(1), map.end());
  EXPECT_NE(map.find(0u), map.end());
}

struct ConvertibleFromNoOp {
  ConvertibleFromNoOp(NoOp) {}  // NOLINT(runtime/explicit)

  template <typename H>
  friend H AbslHashValue(H hash_state, ConvertibleFromNoOp) {
    return H::combine(std::move(hash_state), 1);
  }
};

TEST(HashTest, HeterogeneousCall) {
  EXPECT_NE(Hash<ConvertibleFromNoOp>()(NoOp()),
            Hash<NoOp>()(NoOp()));
}

TEST(IsUniquelyRepresentedTest, SanityTest) {
  using absl::hash_internal::is_uniquely_represented;

  EXPECT_TRUE(is_uniquely_represented<unsigned char>::value);
  EXPECT_TRUE(is_uniquely_represented<int>::value);
  EXPECT_FALSE(is_uniquely_represented<bool>::value);
  EXPECT_FALSE(is_uniquely_represented<int*>::value);
}

struct IntAndString {
  int i;
  std::string s;

  template <typename H>
  friend H AbslHashValue(H hash_state, IntAndString int_and_string) {
    return H::combine(std::move(hash_state), int_and_string.s,
                      int_and_string.i);
  }
};

TEST(HashTest, SmallValueOn64ByteBoundary) {
  Hash<IntAndString>()(IntAndString{0, std::string(63, '0')});
}

struct TypeErased {
  size_t n;

  template <typename H>
  friend H AbslHashValue(H hash_state, const TypeErased& v) {
    v.HashValue(absl::HashState::Create(&hash_state));
    return hash_state;
  }

  void HashValue(absl::HashState state) const {
    absl::HashState::combine(std::move(state), n);
  }
};

TEST(HashTest, TypeErased) {
  EXPECT_TRUE((is_hashable<TypeErased>::value));
  EXPECT_TRUE((is_hashable<std::pair<TypeErased, int>>::value));

  EXPECT_EQ(SpyHash(TypeErased{7}), SpyHash(size_t{7}));
  EXPECT_NE(SpyHash(TypeErased{7}), SpyHash(size_t{13}));

  EXPECT_EQ(SpyHash(std::make_pair(TypeErased{7}, 17)),
            SpyHash(std::make_pair(size_t{7}, 17)));
}

}  // namespace