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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:
 *
 * http://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.channel.ChannelHandlerContext;

/**
 * A {@link Http2FlowController} for controlling the inbound flow of {@code DATA} frames from the remote
 * endpoint.
 */
public interface Http2LocalFlowController extends Http2FlowController {

    /**
     * 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.
     *
     * @param ctx the context from the handler where the frame was read.
     * @param stream the subject stream for the received frame. The connection stream object must
     *            not be used.
     * @param data payload buffer for the frame.
     * @param padding the number of padding bytes found at the end of the frame.
     * @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(ChannelHandlerContext ctx, 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.
     *
     * @param ctx the channel handler context to use when sending a {@code WINDOW_UPDATE} if
     *            appropriate
     * @param stream the stream for which window space should be freed. The connection stream object
     *            must not be used.
     * @param numBytes the number of bytes to be returned to the flow control window.
     * @throws Http2Exception if the number of bytes returned exceeds the {@link #unconsumedBytes}
     *             for the stream.
     */
    void consumeBytes(ChannelHandlerContext ctx, 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);
}