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// Copyright 2013 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_
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#define BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_
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#include "base/base_export.h"
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#include "base/basictypes.h"
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#include "base/memory/scoped_ptr.h"
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#include "base/memory/scoped_vector.h"
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#include "base/synchronization/lock.h"
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#include "base/threading/thread_checker.h"
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class DiscardableMemory;
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// On Android ashmem is used to implement discardable memory. It is backed by a
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// file (descriptor) thus is a limited resource. This allocator minimizes the
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// problem by allocating large ashmem regions internally and returning smaller
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// chunks to the client.
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// Allocated chunks are systematically aligned on a page boundary therefore this
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// allocator should not be used for small allocations.
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// Threading: The allocator must be deleted on the thread it was constructed on
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// although its Allocate() method can be invoked on any thread. See
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// discardable_memory.h for DiscardableMemory's threading guarantees.
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class BASE_EXPORT_PRIVATE DiscardableMemoryAllocator {
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// Note that |name| is only used for debugging/measurement purposes.
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// |ashmem_region_size| is the size that will be used to create the underlying
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// ashmem regions and is expected to be greater or equal than 32 MBytes.
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DiscardableMemoryAllocator(const std::string& name,
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size_t ashmem_region_size);
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~DiscardableMemoryAllocator();
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// Note that the allocator must outlive the returned DiscardableMemory
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scoped_ptr<DiscardableMemory> Allocate(size_t size);
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// Returns the size of the last ashmem region which was created. This is used
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size_t last_ashmem_region_size() const;
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class DiscardableAshmemChunk;
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void DeleteAshmemRegion_Locked(AshmemRegion* region);
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ThreadChecker thread_checker_;
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const std::string name_;
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const size_t ashmem_region_size_;
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size_t last_ashmem_region_size_;
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ScopedVector<AshmemRegion> ashmem_regions_;
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DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAllocator);
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} // namespace internal
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#endif // BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_