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Core functionality for the RSocket library

There is a newer version: 1.1.4

/*
 * Copyright 2015-2018 the original author or authors.
 *
 * 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 io.rsocket.core;

import io.netty.util.collection.IntObjectMap;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;

final class StreamIdSupplier {
  private static final int MASK = 0x7FFFFFFF;

  private static final AtomicLongFieldUpdater STREAM_ID =
      AtomicLongFieldUpdater.newUpdater(StreamIdSupplier.class, "streamId");
  private volatile long streamId;

  // Visible for testing
  StreamIdSupplier(int streamId) {
    this.streamId = streamId;
  }

  static StreamIdSupplier clientSupplier() {
    return new StreamIdSupplier(-1);
  }

  static StreamIdSupplier serverSupplier() {
    return new StreamIdSupplier(0);
  }

  int nextStreamId(IntObjectMap streamIds) {
    int streamId;
    do {
      streamId = (int) STREAM_ID.addAndGet(this, 2) & MASK;
    } while (streamId == 0 || streamIds.containsKey(streamId));
    return streamId;
  }

  boolean isBeforeOrCurrent(int streamId) {
    return this.streamId >= streamId && streamId > 0;
  }
}