components/html_viewer/discardable_memory_allocator.h

   1 // Copyright 2015 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 #ifndef COMPONENTS_HTML_VIEWER_DISCARDABLE_MEMORY_ALLOCATOR_H_
   6 #define COMPONENTS_HTML_VIEWER_DISCARDABLE_MEMORY_ALLOCATOR_H_
   7
   8 #include <list>
   9
  10 #include "base/memory/discardable_memory_allocator.h"
  11
  12 namespace html_viewer {
  13
  14 // A discarable memory allocator which will unallocate chunks on new
  15 // allocations.
  16 class DiscardableMemoryAllocator : public base::DiscardableMemoryAllocator {
  17  public:
  18   class OwnedMemoryChunk;
  19
  20   explicit DiscardableMemoryAllocator(size_t desired_max_memory);
  21   ~DiscardableMemoryAllocator() override;
  22
  23   // Overridden from DiscardableMemoryAllocator:
  24   scoped_ptr<base::DiscardableMemory> AllocateLockedDiscardableMemory(
  25       size_t size) override;
  26
  27  private:
  28   friend class OwnedMemoryChunk;
  29
  30   // Called by OwnedMemoryChunks when they are unlocked. This puts them at the
  31   // end of the live_unlocked_chunks_ list and passes an iterator to their
  32   // position in the unlocked chunk list.
  33   std::list<OwnedMemoryChunk*>::iterator NotifyUnlocked(
  34       OwnedMemoryChunk* chunk);
  35
  36   // Called by OwnedMemoryChunks when they are locked. This removes the passed
  37   // in unlocked chunk list.
  38   void NotifyLocked(std::list<OwnedMemoryChunk*>::iterator it);
  39
  40   // The amount of memory we can allocate before we try to free unlocked
  41   // chunks. We can go over this amount if all callers keep their discardable
  42   // chunks locked.
  43   const size_t desired_max_memory_;
  44
  45   // A count of the sum of memory. Used to trigger discarding the oldest
  46   // memory.
  47   size_t total_live_memory_;
  48
  49   // The number of locked chunks.
  50   int locked_chunks_;
  51
  52   // A linked list of unlocked allocated chunks so that the tail is most
  53   // recently accessed chunks.
  54   std::list<OwnedMemoryChunk*> live_unlocked_chunks_;
  55
  56   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAllocator);
  57 };
  58
  59 }  // namespace html_viewer
  60
  61 #endif  // COMPONENTS_HTML_VIEWER_DISCARDABLE_MEMORY_ALLOCATOR_H_