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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 CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
#define CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
#include <bitset>
#include "base/containers/hash_tables.h"
#include "base/containers/linked_list.h"
#include "base/memory/linked_ptr.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "content/common/content_export.h"
namespace base {
class DiscardableSharedMemory;
}
namespace content {
// Implements a heap of discardable shared memory. A free list is used to keep
// track of free blocks.
class CONTENT_EXPORT DiscardableSharedMemoryHeap {
public:
class CONTENT_EXPORT Span : public base::LinkNode<Span> {
public:
~Span();
base::DiscardableSharedMemory* shared_memory() { return shared_memory_; }
size_t start() const { return start_; }
size_t length() const { return length_; }
private:
friend class DiscardableSharedMemoryHeap;
Span(base::DiscardableSharedMemory* shared_memory,
size_t start,
size_t length);
base::DiscardableSharedMemory* shared_memory_;
size_t start_;
size_t length_;
DISALLOW_COPY_AND_ASSIGN(Span);
};
explicit DiscardableSharedMemoryHeap(size_t block_size);
~DiscardableSharedMemoryHeap();
// Grow heap using |shared_memory| and return a span for this new memory.
// |shared_memory| must be aligned to the block size and |size| must be a
// multiple of the block size.
scoped_ptr<Span> Grow(scoped_ptr<base::DiscardableSharedMemory> shared_memory,
size_t size);
// Merge |span| into the free list. This will coalesce |span| with
// neighboring spans in free list when possible.
void MergeIntoFreeList(scoped_ptr<Span> span);
// Split an allocated span into two spans, one of length |blocks| followed
// by another span of length "span->length - blocks" blocks. Modifies |span|
// to point to the first span of length |blocks|. Return second span.
scoped_ptr<Span> Split(Span* span, size_t blocks);
// Search free list for span that satisfies the request for |blocks| of
// memory. If found, the span is removed from the free list and returned.
scoped_ptr<Span> SearchFreeList(size_t blocks);
// Release shared memory segments that have been purged.
void ReleaseFreeMemory();
private:
scoped_ptr<Span> RemoveFromFreeList(Span* span);
scoped_ptr<Span> Carve(Span* span, size_t blocks);
void RegisterSpan(Span* span);
void UnregisterSpan(Span* span);
void ReleaseMemory(base::DiscardableSharedMemory* shared_memory);
size_t block_size_;
// Discardable shared memory instances.
ScopedVector<base::DiscardableSharedMemory> shared_memory_segments_;
// Mapping from first/last block of span to Span instance.
typedef base::hash_map<size_t, Span*> SpanMap;
SpanMap spans_;
// Linked-list of free discardable memory regions.
base::LinkedList<Span> free_spans_;
DISALLOW_COPY_AND_ASSIGN(DiscardableSharedMemoryHeap);
};
} // namespace content
#endif // CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
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