HashFunctions (MiLib 1.8.3 API)

java.lang.Object
- com.milaboratory.util.HashFunctions

```
public final class HashFunctions
extends Object
```
Hashing algorithms. The algorithms was taken from different open sources.

Links:
http://www.concentric.net/~ttwang/tech/inthash.htm
http://www.burtleburtle.net/bob/hash/doobs.html
http://bretm.home.comcast.net/~bretm/hash
http://www.isthe.com/chongo/tech/comp/fnv/
http://en.wikipedia.org/wiki/Jenkins_hash_function's
http://sites.google.com/site/murmurhash/
http://dmy999.com/article/50/murmurhash-2-java-port
http://en.wikipedia.org/wiki/MurmurHash

Since:

1.0

Author:

Dmitry Bolotin, Stanislav Poslavsky

Field Summary

Fields
Modifier and Type	Field and Description
`static long`	`FNV_BASIS` Fowler/Noll/Vo hash algorithms FNV_BASIS constant
`static long`	`FNV_PRIME_32` Fowler/Noll/Vo hash algorithms FNV_PRIME constant for 32 bit hash
`static long`	`FNV_PRIME_64` Fowler/Noll/Vo hash algorithms FNV_PRIME constant for 64 bit hash

Method Summary

Methods
Modifier and Type	Method and Description
`static int`	`FVN32hash(byte[] bytes)` Fowler-Noll-Vo 32 bit hash (FNV-1a) for bytes array.
`static int`	`FVN32hash(int c)` Fowler-Noll-Vo 32 bit hash (FNV-1a) for integer key.
`static long`	`FVN64hash(byte[] bytes)` Fowler-Noll-Vo 64 bit hash (FNV-1a) for bytes array.
`static long`	`FVN64hash(long c)` Fowler-Noll-Vo 64 bit hash (FNV-1a) for long key.
`static int`	`FVN64to32hash(long c)` Fowler-Noll-Vo 32 bit hash (FNV-1a) for long key.
`static int`	`JenkinWang32shift(int key)` Based on an original suggestion on Robert Jenkin's part in 1997 and Thomas Wang 2007 updates.
`static long`	`JenkinWang64shift(long key)` Based on an original suggestion on Robert Jenkin's part in 1997 and Thomas Wang 2007 updates.
`static int`	`mix(int a, int b, int c)` Robert Jenkins' 96 bit Mix Function.
`static int`	`MurmurHash2(byte[] data)` MurmurHash hash function for bytes array with default seed value equals 0x2f1a32b3.
`static int`	`MurmurHash2(byte[] data, int seed)` MurmurHash hash function for bytes array.
`static int`	`MurmurHash2(int c)` MurmurHash hash function integer with default seed value equals to 0x2f1a32b3.
`static int`	`MurmurHash2(int c, int seed)` MurmurHash hash function integer.
`static int`	`Wang32shiftmult(int key)` This method uses a combination of bit shifts and integer multiplication to hash the input key.
`static int`	`Wang64to32shift(long key)` Hashing long to int.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - FNV_BASIS
```
public static final long FNV_BASIS
```
    Fowler/Noll/Vo hash algorithms FNV_BASIS constant
    
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param
    
    See Also:
    Constant Field Values
  - FNV_PRIME_32
```
public static final long FNV_PRIME_32
```
    Fowler/Noll/Vo hash algorithms FNV_PRIME constant for 32 bit hash
    
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param
    
    See Also:
    Constant Field Values
  - FNV_PRIME_64
```
public static final long FNV_PRIME_64
```
    Fowler/Noll/Vo hash algorithms FNV_PRIME constant for 64 bit hash
    
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param
    
    See Also:
    Constant Field Values
- Method Detail
  - mix
```
public static int mix(int a,
      int b,
      int c)
```
    Robert Jenkins' 96 bit Mix Function.
    Variable 'c' contains the input key. When the mixing is complete, variable 'c' also contains the hash result. Variable 'a', and 'b' contain initialized random bits. Notice the total number of internal state is 96 bits, much larger than the final output of 32 bits. Also notice the sequence of subtractions rolls through variable 'a' to variable 'c' three times. Each row will act on one variable, mixing in information from the other two variables, followed by a shift operation.
    
    Subtraction is similar to multiplication in that changes in upper bits of the key do not influence lower bits of the addition. The 9 bit shift operations in Robert Jenkins' mixing algorithm shifts the key to the right 61 bits in total, and shifts the key to the left 34 bits in total. As the calculation is chained, each exclusive-or doubles the number of states. There are at least 2^9 different combined versions of the original key, shifted by various amounts. That is why a single bit change in the key can influence widely apart bits in the hash result.
    
    The uniform distribution of the hash function can be determined from the nature of the subtraction operation. Look at a single bit subtraction operation between a key, and a random bit. If the random bit is 0, then the key remains unchanged. If the random bit is 1, then the key will be flipped. A carry will occur in the case where both the key bit and the random bit are 1. Subtracting the random bits will cause about half of the key bits to be flipped. So even if the key is not uniform, subtracting the random bits will result in uniform distribution.
    
    Links:
    http://www.concentric.net/~ttwang/tech/inthash.htm
    http://www.burtleburtle.net/bob/hash/doobs.html
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Jenkins_hash_function's
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    
    Parameters:
    a - initialized random bits
    b - initialized random bits
    c - key to be hashed
    
    Returns:
    randomized c bits (hashed c)
  - JenkinWang32shift
```
public static int JenkinWang32shift(int key)
```
    Based on an original suggestion on Robert Jenkin's part in 1997 and Thomas Wang 2007 updates.
    
    Links
    http://www.concentric.net/~ttwang/tech/inthash.htm
    http://en.wikipedia.org/wiki/Jenkins_hash_function's
    
    Parameters:
    key - key to be hashed
    
    Returns:
    hashed value
  - Wang32shiftmult
```
public static int Wang32shiftmult(int key)
```
    This method uses a combination of bit shifts and integer multiplication to hash the input key.
    
    Links
    http://www.concentric.net/~ttwang/tech/inthash.htm
    
    Parameters:
    key - key to be hashed
    
    Returns:
    hashed key
  - JenkinWang64shift
```
public static long JenkinWang64shift(long key)
```
    Based on an original suggestion on Robert Jenkin's part in 1997 and Thomas Wang 2007 updates.
    
    Links
    http://www.concentric.net/~ttwang/tech/inthash.htm
    http://en.wikipedia.org/wiki/Jenkins_hash_function's
    
    Parameters:
    key - key to be hashed
    
    Returns:
    hashed value
  - Wang64to32shift
```
public static int Wang64to32shift(long key)
```
    Hashing long to int.
    
    Links
    http://www.concentric.net/~ttwang/tech/inthash.htm
    
    Parameters:
    key - key to be hashed
    
    Returns:
    hashed value
  - FVN32hash
```
public static int FVN32hash(byte[] bytes)
```
    Fowler-Noll-Vo 32 bit hash (FNV-1a) for bytes array.
    
    Algorithm
```
 hash = offset_basis
 for each octet_of_data to be hashed
    hash = hash xor octet_of_data
    hash = hash * FNV_prime
 return hash
```
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    Parameters:
    bytes - bytes array to hash
    
    Returns:
    hash of the initial bytes array
  - FVN32hash
```
public static int FVN32hash(int c)
```
    Fowler-Noll-Vo 32 bit hash (FNV-1a) for integer key. This is big-endian version (native endianess of JVM).
    
    Algorithm
```
 hash = offset_basis
 for each octet_of_data to be hashed
    hash = hash xor octet_of_data
    hash = hash * FNV_prime
 return hash
```
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    Parameters:
    c - integer key to be hashed
    
    Returns:
    hash 32 bit hash
  - FVN64hash
```
public static long FVN64hash(byte[] bytes)
```
    Fowler-Noll-Vo 64 bit hash (FNV-1a) for bytes array.
    
    Algorithm
```
 hash = offset_basis
 for each octet_of_data to be hashed
    hash = hash xor octet_of_data
    hash = hash * FNV_prime
 return hash
```
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    Parameters:
    bytes - bytes array to hash
    
    Returns:
    hash 64 bit hash
  - FVN64hash
```
public static long FVN64hash(long c)
```
    Fowler-Noll-Vo 64 bit hash (FNV-1a) for long key. This is big-endian version (native endianess of JVM).
    
    Algorithm
```
 hash = offset_basis
 for each octet_of_data to be hashed
    hash = hash xor octet_of_data
    hash = hash * FNV_prime
 return hash
```
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    Parameters:
    c - long key to be hashed
    
    Returns:
    hash 64 bit hash
  - FVN64to32hash
```
public static int FVN64to32hash(long c)
```
    Fowler-Noll-Vo 32 bit hash (FNV-1a) for long key. This is big-endian version (native endianess of JVM).
    
    Algorithm
```
 hash = offset_basis
 for each octet_of_data to be hashed
    hash = hash xor octet_of_data
    hash = hash * FNV_prime
 return hash
```
    Links
    http://www.isthe.com/chongo/tech/comp/fnv/
    http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    Parameters:
    c - long key to be hashed
    
    Returns:
    hash 32 bit hash
  - MurmurHash2
```
public static int MurmurHash2(byte[] data,
              int seed)
```
    MurmurHash hash function for bytes array.
    
    Links
    http://sites.google.com/site/murmurhash/
    http://dmy999.com/article/50/murmurhash-2-java-port
    http://en.wikipedia.org/wiki/MurmurHash
    
    Parameters:
    data - bytes to be hashed
    seed - seed parameter
    
    Returns:
    32 bit hash
  - MurmurHash2
```
public static int MurmurHash2(int c,
              int seed)
```
    MurmurHash hash function integer.
    
    Links
    http://sites.google.com/site/murmurhash/
    http://dmy999.com/article/50/murmurhash-2-java-port
    http://en.wikipedia.org/wiki/MurmurHash
    
    Parameters:
    c - int to be hashed
    seed - seed parameter
    
    Returns:
    32 bit hash
  - MurmurHash2
```
public static int MurmurHash2(byte[] data)
```
    MurmurHash hash function for bytes array with default seed value equals 0x2f1a32b3.
    
    Links
    http://sites.google.com/site/murmurhash/
    http://dmy999.com/article/50/murmurhash-2-java-port
    http://en.wikipedia.org/wiki/MurmurHash
    
    Parameters:
    data - bytes to be hashed
    
    Returns:
    32 bit hash
  - MurmurHash2
```
public static int MurmurHash2(int c)
```
    MurmurHash hash function integer with default seed value equals to 0x2f1a32b3.
    
    Links
    http://sites.google.com/site/murmurhash/
    http://dmy999.com/article/50/murmurhash-2-java-port
    http://en.wikipedia.org/wiki/MurmurHash
    
    Parameters:
    c - int to be hashed\
    
    Returns:
    32 bit hash

Class HashFunctions

Links:

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

FNV_BASIS

Links

FNV_PRIME_32

Links

FNV_PRIME_64

Links

Method Detail

mix

Links:

JenkinWang32shift

Links

Wang32shiftmult

Links

JenkinWang64shift

Links

Wang64to32shift

Links

FVN32hash

Algorithm

Links

FVN32hash

Algorithm

Links

FVN64hash

Algorithm

Links

FVN64hash

Algorithm

Links

FVN64to32hash

Algorithm

Links

MurmurHash2

Links

MurmurHash2

Links

MurmurHash2

Links

MurmurHash2

Links