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   /*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
    * "License"); you may not use this file except in compliance with the License. You may obtain a
    * copy of the License at:
    *
    * https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software distributed under the License
   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing permissions and limitations under
   * the License.
   */
  package io.netty.handler.codec.http2;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.util.internal.UnstableApi;
  
  /**
   * A {@link Http2FlowController} for controlling the inbound flow of {@code DATA} frames from the remote endpoint.
   */
  @UnstableApi
  public interface Http2LocalFlowController extends Http2FlowController {
      /**
       * Sets the writer to be use for sending {@code WINDOW_UPDATE} frames. This must be called before any flow
       * controlled data is received.
       *
       * @param frameWriter the HTTP/2 frame writer.
       */
      Http2LocalFlowController frameWriter(Http2FrameWriter frameWriter);
  
      /**
       * Receives an inbound {@code DATA} frame from the remote endpoint and applies flow control policies to it for both
       * the {@code stream} as well as the connection. If any flow control policies have been violated, an exception is
       * raised immediately, otherwise the frame is considered to have "passed" flow control.
       * <p/>
       * If {@code stream} is {@code null} or closed, flow control should only be applied to the connection window and the
       * bytes are immediately consumed.
       *
       * @param stream the subject stream for the received frame. The connection stream object must not be used. If {@code
       * stream} is {@code null} or closed, flow control should only be applied to the connection window and the bytes are
       * immediately consumed.
       * @param data payload buffer for the frame.
       * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
       *                256 (inclusive).
       * @param endOfStream Indicates whether this is the last frame to be sent from the remote endpoint for this stream.
       * @throws Http2Exception if any flow control errors are encountered.
       */
      void receiveFlowControlledFrame(Http2Stream stream, ByteBuf data, int padding,
                                      boolean endOfStream) throws Http2Exception;
  
      /**
       * Indicates that the application has consumed a number of bytes for the given stream and is therefore ready to
       * receive more data from the remote endpoint. The application must consume any bytes that it receives or the flow
       * control window will collapse. Consuming bytes enables the flow controller to send {@code WINDOW_UPDATE} to
       * restore a portion of the flow control window for the stream.
       * <p/>
       * If {@code stream} is {@code null} or closed (i.e. {@link Http2Stream#state()} method returns {@link
       * Http2Stream.State#CLOSED}), calling this method has no effect.
       *
       * @param stream the stream for which window space should be freed. The connection stream object must not be used.
       * If {@code stream} is {@code null} or closed (i.e. {@link Http2Stream#state()} method returns {@link
       * Http2Stream.State#CLOSED}), calling this method has no effect.
       * @param numBytes the number of bytes to be returned to the flow control window.
       * @return true if a {@code WINDOW_UPDATE} was sent, false otherwise.
       * @throws Http2Exception if the number of bytes returned exceeds the {@link #unconsumedBytes(Http2Stream)} for the
       * stream.
       */
      boolean consumeBytes(Http2Stream stream, int numBytes) throws Http2Exception;
  
      /**
       * The number of bytes for the given stream that have been received but not yet consumed by the
       * application.
       *
       * @param stream the stream for which window space should be freed.
       * @return the number of unconsumed bytes for the stream.
       */
      int unconsumedBytes(Http2Stream stream);
  
      /**
       * Get the initial flow control window size for the given stream. This quantity is measured in number of bytes. Note
       * the unavailable window portion can be calculated by {@link #initialWindowSize()} - {@link
       * #windowSize(Http2Stream)}.
       */
      int initialWindowSize(Http2Stream stream);
  }