com.predic8.membrane.core.transport.http2.PeerFlowControl Maven / Gradle / Ivy

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/* Copyright 2020 predic8 GmbH, www.predic8.com

   Licensed 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 com.predic8.membrane.core.transport.http2;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.concurrent.GuardedBy;

public class PeerFlowControl {
    private static final Logger log = LoggerFactory.getLogger(PeerFlowControl.class);

    private final int streamId;

    @GuardedBy("this")
    public long peerWindowSize;
    @GuardedBy("this")
    public long peerWindowPosition;

    public PeerFlowControl(int streamId, FrameSender sender, Settings peerSettings) {
        this.streamId = streamId;
        peerWindowSize = peerSettings.getInitialWindowSize();
    }

    public synchronized void increment(int delta) {
        peerWindowSize += delta;
        if (log.isDebugEnabled())
            log.debug("stream=" + streamId + " size=" + peerWindowSize + " pos=" + peerWindowPosition + " diff=" + (peerWindowSize - peerWindowPosition));
        notifyAll();
    }

    private void used(int length) {
        peerWindowPosition += length;
        if (log.isDebugEnabled())
            log.debug("stream=" + streamId + " size=" + peerWindowSize + " pos=" + peerWindowPosition + " diff=" + (peerWindowSize - peerWindowPosition));
    }

    private boolean canUse(int length) {
        return peerWindowSize - peerWindowPosition >= length;
    }

    public synchronized void reserve(int wantLength, int streamId) {
        boolean warned = false;
        while(!canUse(wantLength)) {
            if (!warned) {
                log.warn("stream " + streamId + " blocked because of flow control on stream " + this.streamId + ".");
                warned = true;
            }
            try {
                wait();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }

        used(wantLength);
    }

}