io.netty.handler.codec.http2.StreamByteDistributor Maven / Gradle / Ivy
/*
* Copyright 2015 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.util.internal.UnstableApi;
/**
* An object (used by remote flow control) that is responsible for distributing the bytes to be
* written across the streams in the connection.
*/
@UnstableApi
public interface StreamByteDistributor {
/**
* State information for the stream, indicating the number of bytes that are currently
* streamable. This is provided to the {@link #updateStreamableBytes(StreamState)} method.
*/
interface StreamState {
/**
* Gets the stream this state is associated with.
*/
Http2Stream stream();
/**
* Get the amount of bytes this stream has pending to send. The actual amount written must not exceed
* {@link #windowSize()}!
* @return The amount of bytes this stream has pending to send.
* @see Http2CodecUtil#streamableBytes(StreamState)
*/
long pendingBytes();
/**
* Indicates whether or not there are frames pending for this stream.
*/
boolean hasFrame();
/**
* The size (in bytes) of the stream's flow control window. The amount written must not exceed this amount!
* A {@link StreamByteDistributor} needs to know the stream's window size in order to avoid allocating bytes
* if the window size is negative. The window size being {@code 0} may also be significant to determine when if
* an stream has been given a chance to write an empty frame, and also enables optimizations like not writing
* empty frames in some situations (don't write headers until data can also be written).
* @return the size of the stream's flow control window.
* @see Http2CodecUtil#streamableBytes(StreamState)
*/
int windowSize();
}
/**
* Object that performs the writing of the bytes that have been allocated for a stream.
*/
interface Writer {
/**
* Writes the allocated bytes for this stream.
*
* Any {@link Throwable} thrown from this method is considered a programming error.
* A {@code GOAWAY} frame will be sent and the will be connection closed.
* @param stream the stream for which to perform the write.
* @param numBytes the number of bytes to write.
*/
void write(Http2Stream stream, int numBytes);
}
/**
* Called when the streamable bytes for a stream has changed. Until this
* method is called for the first time for a give stream, the stream is assumed to have no
* streamable bytes.
*/
void updateStreamableBytes(StreamState state);
/**
* Explicitly update the dependency tree. This method is called independently of stream state changes.
* @param childStreamId The stream identifier associated with the child stream.
* @param parentStreamId The stream identifier associated with the parent stream. May be {@code 0},
* to make {@code childStreamId} and immediate child of the connection.
* @param weight The weight which is used relative to other child streams for {@code parentStreamId}. This value
* must be between 1 and 256 (inclusive).
* @param exclusive If {@code childStreamId} should be the exclusive dependency of {@code parentStreamId}.
*/
void updateDependencyTree(int childStreamId, int parentStreamId, short weight, boolean exclusive);
/**
* Distributes up to {@code maxBytes} to those streams containing streamable bytes and
* iterates across those streams to write the appropriate bytes. Criteria for
* traversing streams is undefined and it is up to the implementation to determine when to stop
* at a given stream.
*
*
The streamable bytes are not automatically updated by calling this method. It is up to the
* caller to indicate the number of bytes streamable after the write by calling
* {@link #updateStreamableBytes(StreamState)}.
*
* @param maxBytes the maximum number of bytes to write.
* @return {@code true} if there are still streamable bytes that have not yet been written,
* otherwise {@code false}.
* @throws Http2Exception If an internal exception occurs and internal connection state would otherwise be
* corrupted.
*/
boolean distribute(int maxBytes, Writer writer) throws Http2Exception;
}