Method Detail

• goodFastHash

  public static HashFunction goodFastHash(int minimumBits)

  Returns a general-purpose, temporary-use, non-cryptographic hash function. The algorithm the returned function implements is unspecified and subject to change without notice.

  Warning: a new random seed for these functions is chosen each time the Hashing class is loaded. Do not use this method if hash codes may escape the current process in any way, for example being sent over RPC, or saved to disk.

  Repeated calls to this method on the same loaded Hashing class, using the same value for minimumBits, will return identically-behaving HashFunction instances.

  Parameters:

  minimumBits - a positive integer (can be arbitrarily large)

  Returns:

  a hash function, described above, that produces hash codes of length minimumBits or greater

• murmur3_32

  public static HashFunction murmur3_32(int seed)

  Returns a hash function implementing the 32-bit murmur3 algorithm, x86 variant (little-endian variant), using the given seed value.

  The exact C++ equivalent is the MurmurHash3_x86_32 function (Murmur3A).

• murmur3_32

  public static HashFunction murmur3_32()

  Returns a hash function implementing the 32-bit murmur3 algorithm, x86 variant (little-endian variant), using a seed value of zero.

  The exact C++ equivalent is the MurmurHash3_x86_32 function (Murmur3A).

• murmur3_128

  public static HashFunction murmur3_128(int seed)

  Returns a hash function implementing the 128-bit murmur3 algorithm, x64 variant (little-endian variant), using the given seed value.

  The exact C++ equivalent is the MurmurHash3_x64_128 function (Murmur3F).

• murmur3_128

  public static HashFunction murmur3_128()

  Returns a hash function implementing the 128-bit murmur3 algorithm, x64 variant (little-endian variant), using a seed value of zero.

  The exact C++ equivalent is the MurmurHash3_x64_128 function (Murmur3F).

• sipHash24

  public static HashFunction sipHash24()

  Returns a hash function implementing the 64-bit SipHash-2-4 algorithm using a seed value of k = 00 01 02 ....

  Since:

  15.0

• sipHash24

  public static HashFunction sipHash24(long k0,
                                       long k1)

  Returns a hash function implementing the 64-bit SipHash-2-4 algorithm using the given seed.

  Since:

  15.0

• md5

  public static HashFunction md5()

  Returns a hash function implementing the MD5 hash algorithm (128 hash bits) by delegating to the MD5 MessageDigest.

• sha1

  public static HashFunction sha1()

  Returns a hash function implementing the SHA-1 algorithm (160 hash bits) by delegating to the SHA-1 MessageDigest.

• sha256

  public static HashFunction sha256()

  Returns a hash function implementing the SHA-256 algorithm (256 hash bits) by delegating to the SHA-256 MessageDigest.

• sha512

  public static HashFunction sha512()

  Returns a hash function implementing the SHA-512 algorithm (512 hash bits) by delegating to the SHA-512 MessageDigest.

• crc32c

  public static HashFunction crc32c()

  Returns a hash function implementing the CRC32C checksum algorithm (32 hash bits) as described by RFC 3720, Section 12.1.

  Since:

  18.0

• crc32

  public static HashFunction crc32()

  Returns a hash function implementing the CRC-32 checksum algorithm (32 hash bits) by delegating to the CRC32 Checksum.

  To get the long value equivalent to Checksum.getValue() for a HashCode produced by this function, use HashCode.padToLong().

  Since:

  14.0

• adler32

  public static HashFunction adler32()

  Returns a hash function implementing the Adler-32 checksum algorithm (32 hash bits) by delegating to the Adler32 Checksum.

  To get the long value equivalent to Checksum.getValue() for a HashCode produced by this function, use HashCode.padToLong().

  Since:

  14.0

• consistentHash

  public static int consistentHash(HashCode hashCode,
                                   int buckets)

  Assigns to hashCode a "bucket" in the range [0, buckets), in a uniform manner that minimizes the need for remapping as buckets grows. That is, consistentHash(h, n) equals:

  • n - 1, with approximate probability 1/n
  • consistentHash(h, n - 1), otherwise (probability 1 - 1/n)

  See the wikipedia article on consistent hashing for more information.

• consistentHash

  public static int consistentHash(long input,
                                   int buckets)

  Assigns to input a "bucket" in the range [0, buckets), in a uniform manner that minimizes the need for remapping as buckets grows. That is, consistentHash(h, n) equals:

  • n - 1, with approximate probability 1/n
  • consistentHash(h, n - 1), otherwise (probability 1 - 1/n)

  See the wikipedia article on consistent hashing for more information.

• combineOrdered

  public static HashCode combineOrdered(Iterable<HashCode> hashCodes)

  Returns a hash code, having the same bit length as each of the input hash codes, that combines the information of these hash codes in an ordered fashion. That is, whenever two equal hash codes are produced by two calls to this method, it is as likely as possible that each was computed from the same input hash codes in the same order.

  Throws:

  IllegalArgumentException - if hashCodes is empty, or the hash codes do not all have the same bit length

• combineUnordered

  public static HashCode combineUnordered(Iterable<HashCode> hashCodes)

  Returns a hash code, having the same bit length as each of the input hash codes, that combines the information of these hash codes in an unordered fashion. That is, whenever two equal hash codes are produced by two calls to this method, it is as likely as possible that each was computed from the same input hash codes in some order.

  Throws:

  IllegalArgumentException - if hashCodes is empty, or the hash codes do not all have the same bit length