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// Copyright 2016 The Chromium Authors
// 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 <array>
#include <list>
#include <map>
#include <utility>
#include <vector>
#include "net/base/net_export.h"
#include "net/third_party/quiche/src/quiche/http2/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>;
std::array<IdList, spdy::kV3LowestPriority + 1> id_priority_lists_;
// 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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