* Test for avalanche with 2-bit deltas. Most probabilities of output bit(j) differing are well
   * within 50%.
   */
  static void check2BitAvalanche(HashFunction function, int trials, double epsilon) {
    Random rand = new Random(0);
    int keyBits = 32;
    int hashBits = function.bits();
    for (int bit1 = 0; bit1 < keyBits; bit1++) {
      for (int bit2 = 0; bit2 < keyBits; bit2++) {
        if (bit2 <= bit1) continue;

  public static HashFunction goodFastHash(int minimumBits) {
    int bits = checkPositiveAndMakeMultipleOf32(minimumBits);

    if (bits == 32) {
      return Murmur3_32HashFunction.GOOD_FAST_HASH_32;
    }
    if (bits <= 128) {
      return Murmur3_128HashFunction.GOOD_FAST_HASH_128;
    }

    // Otherwise, join together some 128-bit murmur3s
    int hashFunctionsNeeded = (bits + 127) / 128;

  public static HashFunction goodFastHash(int minimumBits) {
    int bits = checkPositiveAndMakeMultipleOf32(minimumBits);

    if (bits == 32) {
      return Murmur3_32HashFunction.GOOD_FAST_HASH_32;
    }
    if (bits <= 128) {
      return Murmur3_128HashFunction.GOOD_FAST_HASH_128;
    }

    // Otherwise, join together some 128-bit murmur3s
    int hashFunctionsNeeded = (bits + 127) / 128;

        @Test
        @DisplayName("Should validate constant bit ranges")
        void shouldValidateConstantBitRanges() {
            // File access constants should fit in lower 16 bits (0x0000FFFF)
            assertTrue(ACE.FILE_READ_DATA <= 0x0000FFFF, "FILE_READ_DATA should fit in lower 16 bits");
            assertTrue(ACE.FILE_WRITE_DATA <= 0x0000FFFF, "FILE_WRITE_DATA should fit in lower 16 bits");

        LockFreeBitArray bits) {
      long bitSize = bits.bitSize();
      long hash64 = Hashing.murmur3_128().hashObject(object, funnel).asLong();
      int hash1 = (int) hash64;
      int hash2 = (int) (hash64 >>> 32);

      boolean bitsChanged = false;
      for (int i = 1; i <= numHashFunctions; i++) {
        int combinedHash = hash1 + (i * hash2);
        // Flip all the bits if it's negative (guaranteed positive number)

        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits);

    /**
     * Queries {@code numHashFunctions} bits of the given bit array, by hashing a user element;
     * returns {@code true} if and only if all selected bits are set.
     */
    <T extends @Nullable Object> boolean mightContain(
        @ParametricNullness T object,

import org.jspecify.annotations.Nullable;

/**
 * An immutable hash code of arbitrary bit length.
 *
 * @author Dimitris Andreou
 * @author Kurt Alfred Kluever
 * @since 11.0
 */
public abstract class HashCode {
  HashCode() {}

  /** Returns the number of bits in this hash code; a positive multiple of 8. */
  public abstract int bits();

  /**

   * This method does so by hashing 64 bits of the IPv6 address into {@code 224.0.0.0/3} (64 bits
   * into 29 bits):
   *
   * <ul>
   *   <li>If the IPv6 address contains an embedded IPv4 address, the function hashes that.
   *   <li>Otherwise, it hashes the upper 64 bits of the IPv6 address.
   * </ul>
   *
   * <p>A "coerced" IPv4 address is equivalent to itself.

A note about ZIP64:

To be backwards compatible the FileHeader has both 32 and 64 bit Size
fields. The 64 bit fields will always contain the correct value and
for normal archives both fields will be the same. For files requiring
the ZIP64 format the 32 bit fields will be 0xffffffff and the 64 bit
fields must be used instead.

[ZIP specification]: https://support.pkware.com/pkzip/appnote
*/
package zip

  // array. The top bits of this value are the remaining bits of the hash value that were not used
  // in the short hash. We saw that a mask of 0x7f would keep the 7-bit value 0x6f from a full
  // hashcode of 0x89abcdef. The imaginary `hash` value would then be the remaining top 25 bits,
  // 0x89abcd80. To this is added (or'd) the `next` value, which is an index within `entries`