base/memory/shared_memory_mapping_unittest.cc

// Copyright 2018 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/memory/shared_memory_mapping.h"

#include <stdint.h>

#include <algorithm>
#include <limits>

#include "base/containers/span.h"
#include "base/memory/read_only_shared_memory_region.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

class SharedMemoryMappingTest : public ::testing::Test {
 protected:
  void CreateMapping(size_t size) {
    auto result = ReadOnlySharedMemoryRegion::Create(size);
    ASSERT_TRUE(result.IsValid());
    write_mapping_ = std::move(result.mapping);
    read_mapping_ = result.region.Map();
    ASSERT_TRUE(read_mapping_.IsValid());
  }

  WritableSharedMemoryMapping write_mapping_;
  ReadOnlySharedMemoryMapping read_mapping_;
};

TEST_F(SharedMemoryMappingTest, Invalid) {
  EXPECT_EQ(nullptr, write_mapping_.GetMemoryAs<uint8_t>());
  EXPECT_EQ(nullptr, read_mapping_.GetMemoryAs<uint8_t>());
  EXPECT_TRUE(write_mapping_.GetMemoryAsSpan<uint8_t>().empty());
  EXPECT_TRUE(read_mapping_.GetMemoryAsSpan<uint8_t>().empty());
  EXPECT_TRUE(write_mapping_.GetMemoryAsSpan<uint8_t>(1).empty());
  EXPECT_TRUE(read_mapping_.GetMemoryAsSpan<uint8_t>(1).empty());
}

TEST_F(SharedMemoryMappingTest, Scalar) {
  CreateMapping(sizeof(uint32_t));

  uint32_t* write_ptr = write_mapping_.GetMemoryAs<uint32_t>();
  EXPECT_NE(nullptr, write_ptr);

  const uint32_t* read_ptr = read_mapping_.GetMemoryAs<uint32_t>();
  EXPECT_NE(nullptr, read_ptr);

  *write_ptr = 0u;
  EXPECT_EQ(0u, *read_ptr);

  *write_ptr = 0x12345678u;
  EXPECT_EQ(0x12345678u, *read_ptr);
}

TEST_F(SharedMemoryMappingTest, SpanWithAutoDeducedElementCount) {
  CreateMapping(sizeof(uint8_t) * 8);

  span<uint8_t> write_span = write_mapping_.GetMemoryAsSpan<uint8_t>();
  ASSERT_EQ(8u, write_span.size());

  span<const uint32_t> read_span = read_mapping_.GetMemoryAsSpan<uint32_t>();
  ASSERT_EQ(2u, read_span.size());

  std::fill(write_span.begin(), write_span.end(), 0);
  EXPECT_EQ(0u, read_span[0]);
  EXPECT_EQ(0u, read_span[1]);

  for (size_t i = 0; i < write_span.size(); ++i)
    write_span[i] = i + 1;
  EXPECT_EQ(0x04030201u, read_span[0]);
  EXPECT_EQ(0x08070605u, read_span[1]);
}

TEST_F(SharedMemoryMappingTest, SpanWithExplicitElementCount) {
  CreateMapping(sizeof(uint8_t) * 8);

  span<uint8_t> write_span = write_mapping_.GetMemoryAsSpan<uint8_t>(8);
  ASSERT_EQ(8u, write_span.size());

  span<uint8_t> write_span_2 = write_mapping_.GetMemoryAsSpan<uint8_t>(4);
  ASSERT_EQ(4u, write_span_2.size());

  span<const uint32_t> read_span = read_mapping_.GetMemoryAsSpan<uint32_t>(2);
  ASSERT_EQ(2u, read_span.size());

  span<const uint32_t> read_span_2 = read_mapping_.GetMemoryAsSpan<uint32_t>(1);
  ASSERT_EQ(1u, read_span_2.size());

  std::fill(write_span.begin(), write_span.end(), 0);
  EXPECT_EQ(0u, read_span[0]);
  EXPECT_EQ(0u, read_span[1]);
  EXPECT_EQ(0u, read_span_2[0]);

  for (size_t i = 0; i < write_span.size(); ++i)
    write_span[i] = i + 1;
  EXPECT_EQ(0x04030201u, read_span[0]);
  EXPECT_EQ(0x08070605u, read_span[1]);
  EXPECT_EQ(0x04030201u, read_span_2[0]);

  std::fill(write_span_2.begin(), write_span_2.end(), 0);
  EXPECT_EQ(0u, read_span[0]);
  EXPECT_EQ(0x08070605u, read_span[1]);
  EXPECT_EQ(0u, read_span_2[0]);
}

TEST_F(SharedMemoryMappingTest, SpanWithZeroElementCount) {
  CreateMapping(sizeof(uint8_t) * 8);

  EXPECT_TRUE(write_mapping_.GetMemoryAsSpan<uint8_t>(0).empty());

  EXPECT_TRUE(read_mapping_.GetMemoryAsSpan<uint8_t>(0).empty());
}

TEST_F(SharedMemoryMappingTest, TooBigScalar) {
  CreateMapping(sizeof(uint8_t));

  EXPECT_EQ(nullptr, write_mapping_.GetMemoryAs<uint32_t>());

  EXPECT_EQ(nullptr, read_mapping_.GetMemoryAs<uint32_t>());
}

TEST_F(SharedMemoryMappingTest, TooBigSpanWithAutoDeducedElementCount) {
  CreateMapping(sizeof(uint8_t));

  EXPECT_TRUE(write_mapping_.GetMemoryAsSpan<uint32_t>().empty());

  EXPECT_TRUE(read_mapping_.GetMemoryAsSpan<uint32_t>().empty());
}

TEST_F(SharedMemoryMappingTest, TooBigSpanWithExplicitElementCount) {
  CreateMapping(sizeof(uint8_t));

  // Deliberately pick element counts such that a naive bounds calculation would
  // overflow.
  EXPECT_TRUE(write_mapping_
                  .GetMemoryAsSpan<uint32_t>(std::numeric_limits<size_t>::max())
                  .empty());

  EXPECT_TRUE(read_mapping_
                  .GetMemoryAsSpan<uint32_t>(std::numeric_limits<size_t>::max())
                  .empty());
}

}  // namespace base