### [Fast Fallback](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-ok-http-client/-builder/fast-fallback/)

Since version 5.0, `OkHttpClient` supports fast fallback, which is our implementation of Happy Eyeballs [RFC 6555](https://datatracker.ietf.org/doc/html/rfc6555).

   * at least for commonly used charsets like UTF-8.
   */

  @Override
  @CanIgnoreReturnValue
  public final Hasher putByte(byte b) {
    buffer.put(b);
    munchIfFull();
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public final Hasher putShort(short s) {
    buffer.putShort(s);
    munchIfFull();

    b ^= b >>> 47;
    b *= K3;
    return b;
  }

  /**
   * Computes intermediate hash of 32 bytes of byte array from the given offset. Results are
   * returned in the output array - this is 12% faster than allocating new arrays every time.
   */
  private static void weakHashLength32WithSeeds(
      byte[] bytes, int offset, long seedA, long seedB, long[] output) {
    long part1 = load64(bytes, offset);

   * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
   * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Floats.asList(array),
   * distance)}, but is considerably faster and avoids allocation and garbage collection.
   *
   * <p>The provided "distance" may be negative, which will rotate left.
   *
   * @since 32.0.0
   */
  public static void rotate(float[] array, int distance) {

 [conscrypt]: https://github.com/google/conscrypt/
 [get_example]: https://raw.github.com/square/okhttp/master/samples/guide/src/main/java/okhttp3/guide/GetExample.java
 [kotlin]: https://kotlinlang.org/
 [okhttp3_pro]: https://raw.githubusercontent.com/square/okhttp/master/okhttp/src/main/resources/META-INF/proguard/okhttp3.pro
 [okhttp]: https://square.github.io/okhttp/

   * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
   * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Bytes.asList(array),
   * distance)}, but is considerably faster and avoids allocation and garbage collection.
   *
   * <p>The provided "distance" may be negative, which will rotate left.
   *
   * @since 32.0.0
   */
  public static void rotate(double[] array, int distance) {

    b ^= b >>> 47;
    b *= K3;
    return b;
  }

  /**
   * Computes intermediate hash of 32 bytes of byte array from the given offset. Results are
   * returned in the output array - this is 12% faster than allocating new arrays every time.
   */
  private static void weakHashLength32WithSeeds(
      byte[] bytes, int offset, long seedA, long seedB, long[] output) {
    long part1 = load64(bytes, offset);

    
    // Second listing should use cache (much faster)
    long start2 = System.currentTimeMillis();
    SmbFile[] files2 = dir.listFiles();
    long time2 = System.currentTimeMillis() - start2;
    
    assertEquals(files1.length, files2.length);
    assertTrue(time2 < time1 / 2);  // Should be significantly faster
}

@Test
public void testDirectoryChangeNotification() throws Exception {

      INSTANCE;

      /*
       * Static final fields are presumed to be fastest, based on our experience with
       * UnsignedBytesBenchmark. TODO(cpovirk): benchmark this
       */
      /*
       * A CopyOnWriteArraySet<WeakReference> is faster than a newSetFromMap of a MapMaker map with
       * weakKeys() and concurrencyLevel(1), even up to at least 12 cached exception types.

      INSTANCE;

      /*
       * Static final fields are presumed to be fastest, based on our experience with
       * UnsignedBytesBenchmark. TODO(cpovirk): benchmark this
       */
      /*
       * A CopyOnWriteArraySet<WeakReference> is faster than a newSetFromMap of a MapMaker map with
       * weakKeys() and concurrencyLevel(1), even up to at least 12 cached exception types.