content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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 com.alibaba.jstorm.common.metric.codahale;
  
  import java.util.Random;
  
  /**
   * @author wange
   * @since 2.1.1
   */
  class ThreadLocalRandom extends Random {
      // same constants as Random, but must be redeclared because private
      private static final long multiplier = 0x5DEECE66DL;
      private static final long addend = 0xBL;
      private static final long mask = (1L << 48) - 1;
  
      /**
       * The random seed. We can't use super.seed.
       */
      private long rnd;
  
      /**
       * Initialization flag to permit calls to setSeed to succeed only while executing the Random
       * constructor.  We can't allow others since it would cause setting seed in one part of a
       * program to unintentionally impact other usages by the thread.
       */
      boolean initialized;
  
      // Padding to help avoid memory contention among seed updates in
      // different TLRs in the common case that they are located near
      // each other.
      private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
  
      /**
       * The actual ThreadLocal
       */
      private static final ThreadLocal<ThreadLocalRandom> localRandom =
              new ThreadLocal<ThreadLocalRandom>() {
                  protected ThreadLocalRandom initialValue() {
                      return new ThreadLocalRandom();
                  }
              };
  
  
      /**
       * Constructor called only by localRandom.initialValue.
       */
      ThreadLocalRandom() {
          super();
          initialized = true;
      }
  
      /**
       * Returns the current thread's {@code ThreadLocalRandom}.
       *
       * @return the current thread's {@code ThreadLocalRandom}
       */
      public static ThreadLocalRandom current() {
          return localRandom.get();
      }
  
      /**
       * Throws {@code UnsupportedOperationException}.  Setting seeds in this generator is not
       * supported.
       *
       * @throws UnsupportedOperationException always
       */
      public void setSeed(long seed) {
          if (initialized)
              throw new UnsupportedOperationException();
          rnd = (seed ^ multiplier) & mask;
      }
  
      protected int next(int bits) {
          rnd = (rnd * multiplier + addend) & mask;
          return (int) (rnd >>> (48 - bits));
      }
  
      /**
       * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive)
       * and bound (exclusive).
       *
       * @param least the least value returned
       * @param bound the upper bound (exclusive)
       * @return the next value
       * @throws IllegalArgumentException if least greater than or equal to bound
       */
      public int nextInt(int least, int bound) {
          if (least >= bound)
              throw new IllegalArgumentException();
          return nextInt(bound - least) + least;
      }
  
      /**
       * Returns a pseudorandom, uniformly distributed value between 0 (inclusive) and the specified
       * value (exclusive).
       *
       * @param n the bound on the random number to be returned.  Must be positive.
       * @return the next value
       * @throws IllegalArgumentException if n is not positive
       */
      public long nextLong(long n) {
          if (n <= 0)
              throw new IllegalArgumentException("n must be positive");
          // Divide n by two until small enough for nextInt. On each
          // iteration (at most 31 of them but usually much less),
          // randomly choose both whether to include high bit in result
          // (offset) and whether to continue with the lower vs upper
          // half (which makes a difference only if odd).
          long offset = 0;
          while (n >= Integer.MAX_VALUE) {
              final int bits = next(2);
              final long half = n >>> 1;
              final long nextn = ((bits & 2) == 0) ? half : n - half;
              if ((bits & 1) == 0)
                  offset += n - nextn;
              n = nextn;
          }
          return offset + nextInt((int) n);
      }
  
      /**
       * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive)
       * and bound (exclusive).
       *
       * @param least the least value returned
       * @param bound the upper bound (exclusive)
       * @return the next value
       * @throws IllegalArgumentException if least greater than or equal to bound
       */
      public long nextLong(long least, long bound) {
          if (least >= bound)
              throw new IllegalArgumentException();
          return nextLong(bound - least) + least;
      }
  
      /**
       * Returns a pseudorandom, uniformly distributed {@code double} value between 0 (inclusive) and
       * the specified value (exclusive).
       *
       * @param n the bound on the random number to be returned.  Must be positive.
       * @return the next value
       * @throws IllegalArgumentException if n is not positive
       */
      public double nextDouble(double n) {
          if (n <= 0)
              throw new IllegalArgumentException("n must be positive");
          return nextDouble() * n;
      }
  
      /**
       * Returns a pseudorandom, uniformly distributed value between the given least value (inclusive)
       * and bound (exclusive).
       *
       * @param least the least value returned
       * @param bound the upper bound (exclusive)
       * @return the next value
       * @throws IllegalArgumentException if least greater than or equal to bound
       */
      public double nextDouble(double least, double bound) {
          if (least >= bound)
              throw new IllegalArgumentException();
          return nextDouble() * (bound - least) + least;
      }
  
      private static final long serialVersionUID = -5851777807851030925L;
  }
  // CHECKSTYLE:ON
  