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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.
#include <list>
#include <map>
#include <utility>
#include <vector>
#include "net/base/net_export.h"
#include "net/third_party/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 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 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 {
// 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(SpdyStreamId id,
SpdyPriority priority,
SpdyStreamId* parent_stream_id,
int* weight,
bool* exclusive);
// Called when a stream is destroyed.
void OnStreamDestruction(SpdyStreamId id);
struct DependencyUpdate {
SpdyStreamId id;
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(SpdyStreamId id,
SpdyPriority new_priority);
// Returns the estimate of dynamically allocated memory in bytes.
size_t EstimateMemoryUsage() const;
// 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_;
// 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(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(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(SpdyStreamId id, IdList::iterator* child);
} // namespace net