text: // 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.
  
  // Unit test for bit_cast template.
  
  #include <cstdint>
  #include <cstring>
  
  #include "gtest/gtest.h"
  #include "absl/base/casts.h"
  #include "absl/base/macros.h"
  
  namespace absl {
  inline namespace lts_2019_08_08 {
  namespace {
  
  template <int N>
  struct marshall { char buf[N]; };
  
  template <typename T>
  void TestMarshall(const T values[], int num_values) {
    for (int i = 0; i < num_values; ++i) {
      T t0 = values[i];
      marshall<sizeof(T)> m0 = absl::bit_cast<marshall<sizeof(T)> >(t0);
      T t1 = absl::bit_cast<T>(m0);
      marshall<sizeof(T)> m1 = absl::bit_cast<marshall<sizeof(T)> >(t1);
      ASSERT_EQ(0, memcmp(&t0, &t1, sizeof(T)));
      ASSERT_EQ(0, memcmp(&m0, &m1, sizeof(T)));
    }
  }
  
  // Convert back and forth to an integral type.  The C++ standard does
  // not guarantee this will work, but we test that this works on all the
  // platforms we support.
  //
  // Likewise, we below make assumptions about sizeof(float) and
  // sizeof(double) which the standard does not guarantee, but which hold on the
  // platforms we support.
  
  template <typename T, typename I>
  void TestIntegral(const T values[], int num_values) {
    for (int i = 0; i < num_values; ++i) {
      T t0 = values[i];
      I i0 = absl::bit_cast<I>(t0);
      T t1 = absl::bit_cast<T>(i0);
      I i1 = absl::bit_cast<I>(t1);
      ASSERT_EQ(0, memcmp(&t0, &t1, sizeof(T)));
      ASSERT_EQ(i0, i1);
    }
  }
  
  TEST(BitCast, Bool) {
    static const bool bool_list[] = { false, true };
    TestMarshall<bool>(bool_list, ABSL_ARRAYSIZE(bool_list));
  }
  
  TEST(BitCast, Int32) {
    static const int32_t int_list[] =
      { 0, 1, 100, 2147483647, -1, -100, -2147483647, -2147483647-1 };
    TestMarshall<int32_t>(int_list, ABSL_ARRAYSIZE(int_list));
  }
  
  TEST(BitCast, Int64) {
    static const int64_t int64_list[] =
      { 0, 1, 1LL << 40, -1, -(1LL<<40) };
    TestMarshall<int64_t>(int64_list, ABSL_ARRAYSIZE(int64_list));
  }
  
  TEST(BitCast, Uint64) {
    static const uint64_t uint64_list[] =
      { 0, 1, 1LLU << 40, 1LLU << 63 };
    TestMarshall<uint64_t>(uint64_list, ABSL_ARRAYSIZE(uint64_list));
  }
  
  TEST(BitCast, Float) {
    static const float float_list[] =
      { 0.0f, 1.0f, -1.0f, 10.0f, -10.0f,
        1e10f, 1e20f, 1e-10f, 1e-20f,
        2.71828f, 3.14159f };
    TestMarshall<float>(float_list, ABSL_ARRAYSIZE(float_list));
    TestIntegral<float, int>(float_list, ABSL_ARRAYSIZE(float_list));
    TestIntegral<float, unsigned>(float_list, ABSL_ARRAYSIZE(float_list));
  }
  
  TEST(BitCast, Double) {
    static const double double_list[] =
      { 0.0, 1.0, -1.0, 10.0, -10.0,
        1e10, 1e100, 1e-10, 1e-100,
        2.718281828459045,
        3.141592653589793238462643383279502884197169399375105820974944 };
    TestMarshall<double>(double_list, ABSL_ARRAYSIZE(double_list));
    TestIntegral<double, int64_t>(double_list, ABSL_ARRAYSIZE(double_list));
    TestIntegral<double, uint64_t>(double_list, ABSL_ARRAYSIZE(double_list));
  }
  
  }  // namespace
  }  // inline namespace lts_2019_08_08
  }  // namespace absl
  