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The Async Http Client (AHC) classes.

There is a newer version: 3.0.0

/*
 * Copyright (c) 2017 AsyncHttpClient Project. All rights reserved.
 *
 * This program is licensed to you under the Apache License Version 2.0,
 * and you may not use this file except in compliance with the Apache License Version 2.0.
 * You may obtain a copy of the Apache License Version 2.0 at
 *     http://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the Apache License Version 2.0 is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
 */
package org.asynchttpclient.netty.channel;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * Semaphore-like API, but without blocking.
 *
 * @author Stepan Koltsov
 */
class NonBlockingSemaphore implements NonBlockingSemaphoreLike {

  private final AtomicInteger permits;

  NonBlockingSemaphore(int permits) {
    this.permits = new AtomicInteger(permits);
  }

  @Override
  public void release() {
    permits.incrementAndGet();
  }

  @Override
  public boolean tryAcquire() {
    for (; ; ) {
      int count = permits.get();
      if (count <= 0) {
        return false;
      }
      if (permits.compareAndSet(count, count - 1)) {
        return true;
      }
    }
  }

  @Override
  public String toString() {
    // mimic toString of Semaphore class
    return super.toString() + "[Permits = " + permits + "]";
  }
}