unsafe_shared_memory_pool.cc 3.3 KB

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  1. // Copyright 2021 The Chromium Authors. All rights reserved.
  2. // Use of this source code is governed by a BSD-style license that can be
  3. // found in the LICENSE file.
  4. #include "base/memory/unsafe_shared_memory_pool.h"
  5. #include "base/logging.h"
  6. namespace {
  7. constexpr size_t kMaxStoredBuffers = 32;
  8. } // namespace
  9. namespace base {
  10. UnsafeSharedMemoryPool::UnsafeSharedMemoryPool() = default;
  11. UnsafeSharedMemoryPool::~UnsafeSharedMemoryPool() = default;
  12. UnsafeSharedMemoryPool::Handle::Handle(
  13. PassKey<UnsafeSharedMemoryPool>,
  14. UnsafeSharedMemoryRegion region,
  15. WritableSharedMemoryMapping mapping,
  16. scoped_refptr<UnsafeSharedMemoryPool> pool)
  17. : region_(std::move(region)),
  18. mapping_(std::move(mapping)),
  19. pool_(std::move(pool)) {
  20. CHECK(pool_);
  21. DCHECK(region_.IsValid());
  22. DCHECK(mapping_.IsValid());
  23. }
  24. UnsafeSharedMemoryPool::Handle::~Handle() {
  25. pool_->ReleaseBuffer(std::move(region_), std::move(mapping_));
  26. }
  27. const UnsafeSharedMemoryRegion& UnsafeSharedMemoryPool::Handle::GetRegion()
  28. const {
  29. return region_;
  30. }
  31. const WritableSharedMemoryMapping& UnsafeSharedMemoryPool::Handle::GetMapping()
  32. const {
  33. return mapping_;
  34. }
  35. std::unique_ptr<UnsafeSharedMemoryPool::Handle>
  36. UnsafeSharedMemoryPool::MaybeAllocateBuffer(size_t region_size) {
  37. AutoLock lock(lock_);
  38. DCHECK_GE(region_size, 0u);
  39. if (is_shutdown_)
  40. return nullptr;
  41. // Only change the configured size if bigger region is requested to avoid
  42. // unncecessary reallocations.
  43. if (region_size > region_size_) {
  44. regions_.clear();
  45. region_size_ = region_size;
  46. }
  47. if (!regions_.empty()) {
  48. auto region = std::move(regions_.back());
  49. regions_.pop_back();
  50. DCHECK_GE(region.first.GetSize(), region_size_);
  51. auto handle = std::make_unique<Handle>(PassKey<UnsafeSharedMemoryPool>(),
  52. std::move(region.first),
  53. std::move(region.second), this);
  54. return handle;
  55. }
  56. auto region = UnsafeSharedMemoryRegion::Create(region_size_);
  57. if (!region.IsValid())
  58. return nullptr;
  59. WritableSharedMemoryMapping mapping = region.Map();
  60. if (!mapping.IsValid())
  61. return nullptr;
  62. return std::make_unique<Handle>(PassKey<UnsafeSharedMemoryPool>(),
  63. std::move(region), std::move(mapping), this);
  64. }
  65. void UnsafeSharedMemoryPool::Shutdown() {
  66. AutoLock lock(lock_);
  67. DCHECK(!is_shutdown_);
  68. is_shutdown_ = true;
  69. regions_.clear();
  70. }
  71. void UnsafeSharedMemoryPool::ReleaseBuffer(
  72. UnsafeSharedMemoryRegion region,
  73. WritableSharedMemoryMapping mapping) {
  74. AutoLock lock(lock_);
  75. // Only return regions which are at least as big as the current configuration.
  76. if (is_shutdown_ || regions_.size() >= kMaxStoredBuffers ||
  77. !region.IsValid() || region.GetSize() < region_size_) {
  78. DLOG(WARNING) << "Not returning SharedMemoryRegion to the pool:"
  79. << " is_shutdown: " << (is_shutdown_ ? "true" : "false")
  80. << " stored regions: " << regions_.size()
  81. << " configured size: " << region_size_
  82. << " this region size: " << region.GetSize()
  83. << " valid: " << (region.IsValid() ? "true" : "false");
  84. return;
  85. }
  86. regions_.emplace_back(std::move(region), std::move(mapping));
  87. }
  88. } // namespace base