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