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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.
#include <list>
#include "base/basictypes.h"
#include "base/lazy_instance.h"
#include "base/sequence_checker.h"
#include "base/synchronization/lock.h"
namespace android_webview {
class GlobalTileManagerClient;
// A global tile manager that keeps track of the number of tile resources. Each
// tile needs file descriptors (typically 2) and there is a soft limit of 1024
// file descriptors per Android process. The GlobalTileManager does not keep
// track of how many tiles each individual view is actually using. The purpose
// of GlobalTileManager is to behave gracefully (as in not crashing) when the
// embedder of webview creates a lot of webviews and draw them at the same time.
class GlobalTileManager {
typedef std::list<GlobalTileManagerClient*> ListType;
typedef ListType::iterator Key;
static GlobalTileManager* GetInstance();
void SetTileLimit(size_t num_tiles_limit);
// Requests the |num_of_tiles| from the available global pool. Calls
// GlobalTileManagerClient.SetNumTiles after the manager determines how many
// tiles are available for the client. If the number of tiles left is not
// enough to satisfy the request, the manager will evict tiles allocated to
// other clients.
// Returns false if the key cannot be found in |mru_list_|.
bool RequestTiles(size_t new_num_of_tiles, Key key);
Key PushBack(GlobalTileManagerClient* client);
// |key| must be already in manager. Move the tile manager client
// corresponding to |key| to most recent. This function should be called after
// RequestTiles.
void DidUse(Key key);
void Remove(Key key);
friend struct base::DefaultLazyInstanceTraits<GlobalTileManager>;
// Continues evicting the inactive views until freeing up at least amount of
// tiles specified by |desired_num_tiles| to draw a view specified by |key|,
// or until all inactive views have been evicted. Returns the amount of
// memory that was actually evicted. This function is called when a
// request cannot be satisfied.
size_t Evict(size_t desired_num_tiles, Key key);
// Check that the sum of all client's tiles is equal to
// total_allocated_tiles_.
bool IsConsistent() const;
size_t num_tiles_limit_;
size_t total_allocated_tiles_;
ListType mru_list_;
base::SequenceChecker sequence_checker_;
} // namespace android_webview