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// Copyright 2014 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.
#ifndef BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_
#define BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_
#include <string>
#include "base/base_export.h"
#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "base/synchronization/lock.h"
namespace base {
namespace internal {
class AshmemRegion;
// Internal class, whose instances are returned to the client of the allocator
// (e.g. DiscardableMemoryAshmem), that mimicks the DiscardableMemory interface.
class BASE_EXPORT_PRIVATE DiscardableAshmemChunk {
public:
~DiscardableAshmemChunk();
// Returns whether the memory is still resident.
bool Lock();
void Unlock();
void* Memory() const;
private:
friend class AshmemRegion;
DiscardableAshmemChunk(AshmemRegion* ashmem_region,
int fd,
void* address,
size_t offset,
size_t size);
AshmemRegion* const ashmem_region_;
const int fd_;
void* const address_;
const size_t offset_;
const size_t size_;
bool locked_;
DISALLOW_COPY_AND_ASSIGN(DiscardableAshmemChunk);
};
// Ashmem regions are backed by a file (descriptor) therefore they are a limited
// resource. This allocator minimizes the problem by allocating large ashmem
// regions internally and returning smaller chunks to the client.
// Allocated chunks are systematically aligned on a page boundary therefore this
// allocator should not be used for small allocations.
class BASE_EXPORT_PRIVATE DiscardableMemoryAshmemAllocator {
public:
// Note that |name| is only used for debugging/measurement purposes.
// |ashmem_region_size| is the size that will be used to create the underlying
// ashmem regions and is expected to be greater or equal than 32 MBytes.
DiscardableMemoryAshmemAllocator(const std::string& name,
size_t ashmem_region_size);
~DiscardableMemoryAshmemAllocator();
// Note that the allocator must outlive the returned DiscardableAshmemChunk
// instance.
scoped_ptr<DiscardableAshmemChunk> Allocate(size_t size);
// Returns the size of the last ashmem region which was created. This is used
// for testing only.
size_t last_ashmem_region_size() const;
private:
friend class AshmemRegion;
void DeleteAshmemRegion_Locked(AshmemRegion* region);
const std::string name_;
const size_t ashmem_region_size_;
mutable Lock lock_;
size_t last_ashmem_region_size_;
ScopedVector<AshmemRegion> ashmem_regions_;
DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAshmemAllocator);
};
} // namespace internal
} // namespace base
#endif // BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_
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