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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_HTTP2_PRIORITY_DEPENDENCIES_H_
#define NET_HTTP2_PRIORITY_DEPENDENCIES_H_
#include <list>
#include <map>
#include "net/base/net_export.h"
#include "net/spdy/spdy_protocol.h"
namespace net {
// A helper class encapsulating the state and logic to set dependencies of
// HTTP2 streams based on their SpdyPriority and the ordering
// of creation and deletion of the streams.
class NET_EXPORT_PRIVATE Http2PriorityDependencies {
public:
Http2PriorityDependencies();
~Http2PriorityDependencies();
// Called when a stream SYN is sent to the server. Note that in the
// case of server push, a stream may be created without this routine
// being called. In such cases, the client ignores the stream's priority
// (as the server is effectively overriding the client's notions of
// priority anyway).
// On return, |*dependent_stream_id| is set to the stream id that
// this stream should be made dependent on, and |*exclusive| set to
// whether that dependency should be exclusive.
void OnStreamSynSent(SpdyStreamId id,
SpdyPriority priority,
SpdyStreamId* dependent_stream_id,
bool* exclusive);
void OnStreamDestruction(SpdyStreamId id);
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<SpdyStreamId, SpdyPriority>>;
using EntryMap = std::map<SpdyStreamId, IdList::iterator>;
IdList id_priority_lists_[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_;
};
} // namespace net
#endif // NET_HTTP2_PRIORITY_DEPENDENCIES_H_
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