FlowControlFilter.h

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/*
 *  Copyright (c) 2015-present, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */
#pragma once

#include <proxygen/lib/http/Window.h>
#include <proxygen/lib/http/codec/HTTPCodecFilter.h>

namespace folly {
class IOBufQueue;
}

namespace proxygen {

class FlowControlFilter:
      public PassThroughHTTPCodecFilter {
 public:
  class Callback {
   public:
    virtual ~Callback() {}
    virtual void onConnectionSendWindowOpen() = 0;
    virtual void onConnectionSendWindowClosed() = 0;
  };

  explicit
  FlowControlFilter(Callback& callback,
                    folly::IOBufQueue& writeBuf,
                    HTTPCodec* codec,
                    uint32_t recvCapacity = 0);

  void setReceiveWindowSize(folly::IOBufQueue& writeBuf, uint32_t capacity);

  bool ingressBytesProcessed(folly::IOBufQueue& writeBuf, uint32_t delta);

  uint32_t getAvailableSend() const;

  // Filter functions

  bool isReusable() const override;

  void onBody(StreamID stream, std::unique_ptr<folly::IOBuf> chain,
              uint16_t padding) override;

  void onWindowUpdate(StreamID stream, uint32_t amount) override;

  size_t generateBody(folly::IOBufQueue& writeBuf,
                      StreamID stream,
                      std::unique_ptr<folly::IOBuf> chain,
                      folly::Optional<uint8_t> padding,
                      bool eom) override;

  size_t generateWindowUpdate(folly::IOBufQueue& writeBuf,
                              StreamID stream,
                              uint32_t delta) override;

 private:

  Callback& notify_;
  Window recvWindow_;
  Window sendWindow_;
  int32_t toAck_{0};
  bool error_:1;
  bool sendsBlocked_:1;
};

}