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- // Copyright 2016 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 NET_SPDY_HTTP2_PRIORITY_DEPENDENCIES_H_
- #define NET_SPDY_HTTP2_PRIORITY_DEPENDENCIES_H_
- #include <list>
- #include <map>
- #include <utility>
- #include <vector>
- #include "net/base/net_export.h"
- #include "net/third_party/quiche/src/quiche/spdy/core/spdy_protocol.h"
- namespace net {
- // A helper class encapsulating the state and logic to set the priority fields
- // for HTTP/2 streams based on their spdy::SpdyPriority and the ordering of
- // creation and deletion of the streams. This implentation includes a gross hack
- // in which the HTTP/2 weight is set to a transformation of the
- // spdy::SpdyPriority value in order to support servers which do not honor
- // HTTP/2 stream dependencies and instead treat the weight value like a SPDY/3
- // priority.
- // TODO(rch): Eliminate this gross hack when servers no longer act like this.
- class NET_EXPORT_PRIVATE Http2PriorityDependencies {
- public:
- Http2PriorityDependencies();
- ~Http2PriorityDependencies();
- // Called when a stream is created. This is used for both client-initiated
- // and server-initiated (pushed) streams.
- // On return, |*parent_stream_id| is set to the stream id that should become
- // the parent of this stream, |*exclusive| is set to whether that dependency
- // should be exclusive, and |*weight| is set to the relative weight for the
- // created stream given this priority.
- void OnStreamCreation(spdy::SpdyStreamId id,
- spdy::SpdyPriority priority,
- spdy::SpdyStreamId* parent_stream_id,
- int* weight,
- bool* exclusive);
- // Called when a stream is destroyed.
- void OnStreamDestruction(spdy::SpdyStreamId id);
- struct DependencyUpdate {
- spdy::SpdyStreamId id;
- spdy::SpdyStreamId parent_stream_id;
- int weight;
- bool exclusive;
- };
- // Called when a stream's priority has changed. Returns a list of
- // dependency updates that should be sent to the server to describe
- // the requested priority change. The updates should be sent in the
- // given order.
- std::vector<DependencyUpdate> OnStreamUpdate(spdy::SpdyStreamId id,
- spdy::SpdyPriority new_priority);
- private:
- // The requirements for the internal data structure for this class are:
- // a) Constant time insertion of entries at the end of the list,
- // b) Fast removal of any entry based on its id.
- // c) Constant time lookup of the entry at the end of the list.
- // std::list would satisfy (a) & (c), but some form of map is
- // needed for (b). The priority must be included in the map
- // entries so that deletion can determine which list in id_priority_lists_
- // to erase from.
- using IdList = std::list<std::pair<spdy::SpdyStreamId, spdy::SpdyPriority>>;
- using EntryMap = std::map<spdy::SpdyStreamId, IdList::iterator>;
- IdList id_priority_lists_[spdy::kV3LowestPriority + 1];
- // Tracks the location of an id anywhere in the above vector of lists.
- // Iterators to list elements remain valid until those particular elements
- // are erased.
- EntryMap entry_by_stream_id_;
- // Finds the lowest-priority stream that has a priority >= |priority|.
- // Returns false if there are no such streams.
- // Otherwise, returns true and sets |*bound|.
- bool PriorityLowerBound(spdy::SpdyPriority priority, IdList::iterator* bound);
- // Finds the stream just above |id| in the total order.
- // Returns false if there are no streams with a higher priority.
- // Otherwise, returns true and sets |*parent|.
- bool ParentOfStream(spdy::SpdyStreamId id, IdList::iterator* parent);
- // Finds the stream just below |id| in the total order.
- // Returns false if there are no streams with a lower priority.
- // Otherwise, returns true and sets |*child|.
- bool ChildOfStream(spdy::SpdyStreamId id, IdList::iterator* child);
- };
- } // namespace net
- #endif // NET_SPDY_HTTP2_PRIORITY_DEPENDENCIES_H_
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