package com.carrotsearch.hppc;

import java.security.PrivilegedAction;
import java.util.logging.Level;
import java.util.logging.Logger;

Constants used as defaults in containers.
See Also:
HashContainers/**
 * Constants used as defaults in containers.
 * 
 * @see HashContainers
 */
public final class Containers {
  
The default number of expected elements for containers.
/**
   * The default number of expected elements for containers.
   */
  public final static int DEFAULT_EXPECTED_ELEMENTS = 4;
  
  
External initial seed value. We do not care about multiple assignments 
so not volatile.
See Also:
randomSeed64()/**
   * External initial seed value. We do not care about multiple assignments 
   * so not volatile.
   * 
   * @see #randomSeed64()
   */
  private static String testsSeedProperty;
  
  
Unique marker for testsSeedProperty. /**
   * Unique marker for {@link #testsSeedProperty}.
   */
  private final static String NOT_AVAILABLE = new String();

  private Containers() {}

  
Provides a (possibly) random initial seed for randomized stuff. 
If tests.seed property is available and accessible,
the returned value will be derived from the value of that property
and will be constant to ensure reproducibility in presence of the 
randomized testing package.
See Also:
https://github.com/carrotsearch/randomizedtesting/**
   * Provides a (possibly) random initial seed for randomized stuff. 
   * 
   * If <code>tests.seed</code> property is available and accessible,
   * the returned value will be derived from the value of that property
   * and will be constant to ensure reproducibility in presence of the 
   * randomized testing package.
   * 
   * @see "https://github.com/carrotsearch/randomizedtesting"
   */
  @SuppressForbidden
  public static long randomSeed64() {
    if (testsSeedProperty == null) {
      try {
        testsSeedProperty = java.security.AccessController.doPrivileged(new PrivilegedAction<String>() {
          @Override
          public String run() {
            return System.getProperty("tests.seed", NOT_AVAILABLE);
          }
        });
      } catch (SecurityException e) {
        // If failed on security exception, don't panic.
        testsSeedProperty = NOT_AVAILABLE;
        Logger.getLogger(Containers.class.getName())
          .log(Level.INFO, "Failed to read 'tests.seed' property for initial random seed.", e);
      }
    }

    long initialSeed;
    if (testsSeedProperty != NOT_AVAILABLE) {
      initialSeed = testsSeedProperty.hashCode();
    } else {
      // Mix something that is changing over time (nanoTime)
      // ... with something that is thread-local and relatively unique 
      //     even for very short time-spans (new Object's address from a TLAB).
      initialSeed = System.nanoTime() ^ 
                    System.identityHashCode(new Object());
    }
    return BitMixer.mix64(initialSeed);
  }

  
Reset state for tests.
/**
   * Reset state for tests.
   */
  static void test$reset() {
    testsSeedProperty = null;
  }
}