base/memory/discardable_memory_shmem_allocator.cc

   1 // Copyright 2014 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
   5 #include "base/memory/discardable_memory_shmem_allocator.h"
   6
   7 #include "base/lazy_instance.h"
   8 #include "base/logging.h"
   9 #include "base/memory/discardable_shared_memory.h"
  10
  11 namespace base {
  12 namespace {
  13
  14 class DiscardableMemoryShmemChunkImpl : public DiscardableMemoryShmemChunk {
  15  public:
  16   explicit DiscardableMemoryShmemChunkImpl(
  17       scoped_ptr<DiscardableSharedMemory> shared_memory)
  18       : shared_memory_(shared_memory.Pass()) {}
  19
  20   // Overridden from DiscardableMemoryShmemChunk:
  21   bool Lock() override { return false; }
  22   void Unlock() override {
  23     shared_memory_->Unlock(0, 0);
  24     shared_memory_.reset();
  25   }
  26   void* Memory() const override { return shared_memory_->memory(); }
  27
  28  private:
  29   scoped_ptr<DiscardableSharedMemory> shared_memory_;
  30
  31   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryShmemChunkImpl);
  32 };
  33
  34 // Default allocator implementation that allocates in-process
  35 // DiscardableSharedMemory instances.
  36 class DiscardableMemoryShmemAllocatorImpl
  37     : public DiscardableMemoryShmemAllocator {
  38  public:
  39   // Overridden from DiscardableMemoryShmemAllocator:
  40   scoped_ptr<DiscardableMemoryShmemChunk>
  41   AllocateLockedDiscardableMemory(size_t size) override {
  42     scoped_ptr<DiscardableSharedMemory> memory(new DiscardableSharedMemory);
  43     if (!memory->CreateAndMap(size))
  44       return nullptr;
  45
  46     return make_scoped_ptr(new DiscardableMemoryShmemChunkImpl(memory.Pass()));
  47   }
  48 };
  49
  50 LazyInstance<DiscardableMemoryShmemAllocatorImpl>::Leaky g_default_allocator =
  51     LAZY_INSTANCE_INITIALIZER;
  52
  53 DiscardableMemoryShmemAllocator* g_allocator = nullptr;
  54
  55 }  // namespace
  56
  57 // static
  58 void DiscardableMemoryShmemAllocator::SetInstance(
  59     DiscardableMemoryShmemAllocator* allocator) {
  60   DCHECK(allocator);
  61
  62   // Make sure this function is only called once before the first call
  63   // to GetInstance().
  64   DCHECK(!g_allocator);
  65
  66   g_allocator = allocator;
  67 }
  68
  69 // static
  70 DiscardableMemoryShmemAllocator*
  71 DiscardableMemoryShmemAllocator::GetInstance() {
  72   if (!g_allocator)
  73     g_allocator = g_default_allocator.Pointer();
  74
  75   return g_allocator;
  76 }
  77
  78 }  // namespace base