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| 1 // Copyright (c) 2016 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef NET_SPDY_WRITE_SCHEDULER_H_ | |
| 6 #define NET_SPDY_WRITE_SCHEDULER_H_ | |
| 7 | |
| 8 #include <tuple> | |
| 9 #include <vector> | |
| 10 | |
| 11 #include "net/base/net_export.h" | |
| 12 #include "net/spdy/spdy_protocol.h" | |
| 13 | |
| 14 namespace net { | |
| 15 | |
| 16 // Abstract superclass for classes that decide which SPDY or HTTP/2 stream to | |
| 17 // write next. Concrete subclasses implement various scheduling policies: | |
| 18 // | |
| 19 // PriorityWriteScheduler: implements SPDY priority-based stream scheduling, | |
| 20 // where (writable) higher-priority streams are always given precedence | |
| 21 // over lower-priority streams. | |
| 22 // | |
| 23 // Http2PriorityWriteScheduler: implements SPDY priority-based stream | |
| 24 // scheduling coupled with the HTTP/2 stream dependency model. This is only | |
| 25 // intended as a transitional step towards Http2WeightedWriteScheduler. | |
| 26 // | |
| 27 // Http2WeightedWriteScheduler (coming soon): implements the HTTP/2 stream | |
| 28 // dependency model with weighted stream scheduling, fully conforming to | |
| 29 // RFC 7540. | |
| 30 // | |
| 31 // The type used to represent stream IDs (StreamIdType) is templated in order | |
| 32 // to allow for use by both SPDY and QUIC codebases. It must be a POD that | |
| 33 // supports comparison (i.e., a numeric type). | |
| 34 // | |
| 35 // Each stream can be in one of two states: ready or not ready (for writing). | |
| 36 // Ready state is changed by calling the MarkStreamReady() and | |
| 37 // MarkStreamNotReady() methods. Only streams in the ready state can be | |
| 38 // returned by PopNextReadyStream(); when returned by that method, the stream's | |
| 39 // state changes to not ready. | |
| 40 template <typename StreamIdType> | |
| 41 class NET_EXPORT_PRIVATE WriteScheduler { | |
| 42 public: | |
| 43 typedef StreamPrecedence<StreamIdType> StreamPrecedenceType; | |
| 44 | |
| 45 virtual ~WriteScheduler() {} | |
| 46 | |
| 47 // Registers new stream |stream_id| with the scheduler, assigning it the | |
| 48 // given precedence. If the scheduler supports stream dependencies, the | |
| 49 // stream is inserted into the dependency tree under | |
| 50 // |precedence.parent_id()|. | |
| 51 // | |
| 52 // Preconditions: |stream_id| should be unregistered, and | |
| 53 // |precedence.parent_id()| should be registered or |kHttp2RootStreamId|. | |
| 54 virtual void RegisterStream(StreamIdType stream_id, | |
| 55 const StreamPrecedenceType& precedence) = 0; | |
| 56 | |
| 57 // Unregisters the given stream from the scheduler, which will no longer keep | |
| 58 // state for it. | |
| 59 // | |
| 60 // Preconditions: |stream_id| should be registered. | |
| 61 virtual void UnregisterStream(StreamIdType stream_id) = 0; | |
| 62 | |
| 63 // Returns true if the given stream is currently registered. | |
| 64 virtual bool StreamRegistered(StreamIdType stream_id) const = 0; | |
| 65 | |
| 66 // Returns the precedence of the specified stream. If the scheduler supports | |
| 67 // stream dependencies, calling |parent_id()| on the return value returns the | |
| 68 // stream's parent, and calling |exclusive()| returns true iff the specified | |
| 69 // stream is an only child of the parent stream. | |
| 70 // | |
| 71 // Preconditions: |stream_id| should be registered. | |
| 72 virtual StreamPrecedenceType GetStreamPrecedence( | |
| 73 StreamIdType stream_id) const = 0; | |
| 74 | |
| 75 // Updates the precedence of the given stream. If the scheduler supports | |
| 76 // stream dependencies, |stream_id|'s parent will be updated to be | |
| 77 // |precedence.parent_id()| if it is not already. | |
| 78 // | |
| 79 // Preconditions: |stream_id| should be unregistered, and | |
| 80 // |precedence.parent_id()| should be registered or |kHttp2RootStreamId|. | |
| 81 virtual void UpdateStreamPrecedence( | |
| 82 StreamIdType stream_id, | |
| 83 const StreamPrecedenceType& precedence) = 0; | |
| 84 | |
| 85 // Returns child streams of the given stream, if any. If the scheduler | |
| 86 // doesn't support stream dependencies, returns an empty vector. | |
| 87 // | |
| 88 // Preconditions: |stream_id| should be registered. | |
| 89 virtual std::vector<StreamIdType> GetStreamChildren( | |
| 90 StreamIdType stream_id) const = 0; | |
| 91 | |
| 92 // Records time (in microseconds) of a read/write event for the given | |
| 93 // stream. | |
| 94 // | |
| 95 // Preconditions: |stream_id| should be registered. | |
| 96 virtual void RecordStreamEventTime(StreamIdType stream_id, | |
| 97 int64_t now_in_usec) = 0; | |
| 98 | |
| 99 // Returns time (in microseconds) of the last read/write event for a stream | |
| 100 // with higher priority than the priority of the given stream, or 0 if there | |
| 101 // is no such event. | |
| 102 // | |
| 103 // Preconditions: |stream_id| should be registered. | |
| 104 virtual int64_t GetLatestEventWithPrecedence( | |
| 105 StreamIdType stream_id) const = 0; | |
| 106 | |
| 107 // If the scheduler has any ready streams, returns the next scheduled | |
| 108 // ready stream, in the process transitioning the stream from ready to not | |
| 109 // ready. | |
| 110 // | |
| 111 // Preconditions: |HasReadyStreams() == true| | |
| 112 virtual StreamIdType PopNextReadyStream() = 0; | |
| 113 | |
| 114 // If the scheduler has any ready streams, returns the next scheduled | |
| 115 // ready stream and its priority, in the process transitioning the stream from | |
| 116 // ready to not ready. | |
| 117 // | |
| 118 // Preconditions: |HasReadyStreams() == true| | |
| 119 virtual std::tuple<StreamIdType, StreamPrecedenceType> | |
| 120 PopNextReadyStreamAndPrecedence() = 0; | |
| 121 | |
| 122 // Returns true if there's another stream ahead of the given stream in the | |
| 123 // scheduling queue. This function can be called to see if the given stream | |
| 124 // should yield work to another stream. | |
| 125 // | |
| 126 // Preconditions: |stream_id| should be registered. | |
| 127 virtual bool ShouldYield(StreamIdType stream_id) const = 0; | |
| 128 | |
| 129 // Marks the stream as ready to write. If the stream was already ready, does | |
| 130 // nothing. If add_to_front is true, the stream is scheduled ahead of other | |
| 131 // streams of the same priority/weight, otherwise it is scheduled behind them. | |
| 132 // | |
| 133 // Preconditions: |stream_id| should be registered. | |
| 134 virtual void MarkStreamReady(StreamIdType stream_id, bool add_to_front) = 0; | |
| 135 | |
| 136 // Marks the stream as not ready to write. If the stream is not registered or | |
| 137 // not ready, does nothing. | |
| 138 // | |
| 139 // Preconditions: |stream_id| should be registered. | |
| 140 virtual void MarkStreamNotReady(StreamIdType stream_id) = 0; | |
| 141 | |
| 142 // Returns true iff the scheduler has any ready streams. | |
| 143 virtual bool HasReadyStreams() const = 0; | |
| 144 | |
| 145 // Returns the number of streams currently marked ready. | |
| 146 virtual size_t NumReadyStreams() const = 0; | |
| 147 }; | |
| 148 | |
| 149 } // namespace net | |
| 150 | |
| 151 #endif // NET_SPDY_WRITE_SCHEDULER_H_ | |
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Chromium Code Reviews
Issue 2832973003:
Split net/spdy into core and chromium subdirectories. (Closed)
