HashProvider.HashMethod (bloom-filter 1.0.3 API)

java.lang.Object
- java.lang.Enum<HashProvider.HashMethod>
- - orestes.bloomfilter.HashProvider.HashMethod

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<HashProvider.HashMethod>

Enclosing class:

HashProvider
```
public static enum HashProvider.HashMethod
extends java.lang.Enum<HashProvider.HashMethod>
```
Different types of hash functions that can be used.

Enum Constant Summary

Enum Constants
Enum Constant and Description
`Adler32` Generates hash values using the Adler32 Checksum algorithm.
`CarterWegman` Generates hash values using the Carter Wegman function (Wikipedia), which is a universal hashing function.
`CRC32` Generates hash values using a Cyclic Redundancy Check (CRC32).
`FNVWithLCG` Uses the Fowler–Noll–Vo (FNV) hash function to generate a hash values.
`MD2` Generates a hash value using MD2.
`MD5` Generates a hash value using the cryptographic MD5 hash function.
`Murmur2` Generates hash values using the Murmur 2 hash, see: https://code.google.com/p/smhasher/wiki/MurmurHash2 Murmur 2 is very fast.
`Murmur3` Generates hash values using the Murmur 3 hash, see: https://code.google.com/p/smhasher/wiki/MurmurHash3 Its uniformity is comparable to that of cryptographic hash functions but considerably faster.
`Murmur3KirschMitzenmacher` Uses a the Murmur 3 hash in combination with a performance optimization described by Kirsch and Mitzenmacher, see: http://www.eecs.harvard.edu/~kirsch/pubs/bbbf/esa06.pdf - hash values are generated through the scheme h_i = (h1 + i*h2) mod m Though this method is asymptotically optimal our experiements revealed that real-world performance is not as good as pure Murmur 3 hashes or cryptographic hash functions, in particular for random words.
`RNG` Generates hash values using the Java Random Number Generator (RNG) which is a Linear Congruential Generator (LCG), implementing the following formula: `number_i+1 = (a * number_i + countingBits) mod size` The RNG is initialized using the value to be hashed.
`SHA1` Generates a hash value using the cryptographic SHA1 hash function.
`SHA256` Generates a hash value using the cryptographic SHA-256 hash function.
`SHA384` Generates a hash value using the cryptographic SHA-384 hash function.
`SHA512` Generates a hash value using the cryptographic SHA-512 hash function.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`HashProvider.HashFunction`	`getHashFunction()`
`static HashProvider.HashMethod`	`valueOf(java.lang.String name)` Returns the enum constant of this type with the specified name.
`static HashProvider.HashMethod[]`	`values()` Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum
clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait

- Enum Constant Detail
  - RNG
```
public static final HashProvider.HashMethod RNG
```
    Generates hash values using the Java Random Number Generator (RNG) which is a Linear Congruential Generator (LCG), implementing the following formula:
    number_i+1 = (a * number_i + countingBits) mod size
    
    The RNG is initialized using the value to be hashed.
  - CarterWegman
```
public static final HashProvider.HashMethod CarterWegman
```
    Generates hash values using the Carter Wegman function (Wikipedia), which is a universal hashing function. It thus has optimal guarantees for the uniformity of generated hash values. On the downside, the performance is not optimal, as arithmetic operations on large numbers have to be performed.
  - CRC32
```
public static final HashProvider.HashMethod CRC32
```
    Generates hash values using a Cyclic Redundancy Check (CRC32). CRC is designed as a checksum for data integrity not as hash function but exhibits very good uniformity and is relatively fast.
  - Adler32
```
public static final HashProvider.HashMethod Adler32
```
    Generates hash values using the Adler32 Checksum algorithm. Adler32 is comparable to CRC32 but is faster at the cost of a less uniform distribution of hash values.
  - Murmur2
```
public static final HashProvider.HashMethod Murmur2
```
    Generates hash values using the Murmur 2 hash, see: https://code.google.com/p/smhasher/wiki/MurmurHash2
    Murmur 2 is very fast. However, there is a flaw that affects the uniformity of some input values (for instance increasing integers as strings).
  - Murmur3
```
public static final HashProvider.HashMethod Murmur3
```
    Generates hash values using the Murmur 3 hash, see: https://code.google.com/p/smhasher/wiki/MurmurHash3
    Its uniformity is comparable to that of cryptographic hash functions but considerably faster.
  - Murmur3KirschMitzenmacher
```
public static final HashProvider.HashMethod Murmur3KirschMitzenmacher
```
    Uses a the Murmur 3 hash in combination with a performance optimization described by Kirsch and Mitzenmacher, see: http://www.eecs.harvard.edu/~kirsch/pubs/bbbf/esa06.pdf - hash values are generated through the scheme h_i = (h1 + i*h2) mod m
    Though this method is asymptotically optimal our experiements revealed that real-world performance is not as good as pure Murmur 3 hashes or cryptographic hash functions, in particular for random words.
  - FNVWithLCG
```
public static final HashProvider.HashMethod FNVWithLCG
```
    Uses the Fowler–Noll–Vo (FNV) hash function to generate a hash values. It is superior to the standard implementation in Arrays and can be easily implemented in most languages. Hashing then uses the very simple Linear Congruential Generator scheme and the Java initialization constants. This method is intended to be employed if the bloom filter has to be used in a language which doesn't support any of the other hash functions. This hash function can then easily be implemented.
  - MD2
```
public static final HashProvider.HashMethod MD2
```
    Generates a hash value using MD2. MD2 is rather slow an not as evenely distributed as other cryptographic hash functions
  - MD5
```
public static final HashProvider.HashMethod MD5
```
    Generates a hash value using the cryptographic MD5 hash function. It is fast and has good guarantees for the uniformity of generated hash values, as the hash functions are designed for cryptographic use.
  - SHA1
```
public static final HashProvider.HashMethod SHA1
```
    Generates a hash value using the cryptographic SHA1 hash function. It is fast but uniformity of hash values is better for the second generation of SHA (256,384,512).
  - SHA256
```
public static final HashProvider.HashMethod SHA256
```
    Generates a hash value using the cryptographic SHA-256 hash function. It is fast and has good guarantees for the uniformity of generated hash values, as the hash functions are designed for cryptographic use.
  - SHA384
```
public static final HashProvider.HashMethod SHA384
```
    Generates a hash value using the cryptographic SHA-384 hash function. It is fast and has good guarantees for the uniformity of generated hash values, as the hash functions are designed for cryptographic use.
  - SHA512
```
public static final HashProvider.HashMethod SHA512
```
    Generates a hash value using the cryptographic SHA-512 hash function. It is fast and has good guarantees for the uniformity of generated hash values, as the hash functions are designed for cryptographic use.
- Method Detail
  - values
```
public static HashProvider.HashMethod[] values()
```
    Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:
```
for (HashProvider.HashMethod c : HashProvider.HashMethod.values())
    System.out.println(c);
```
    Returns:
    
    an array containing the constants of this enum type, in the order they are declared
  - valueOf
```
public static HashProvider.HashMethod valueOf(java.lang.String name)
```
    Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
    
    Parameters:
    
    name - the name of the enum constant to be returned.
    
    Returns:
    
    the enum constant with the specified name
    
    Throws:
    
    java.lang.IllegalArgumentException - if this enum type has no constant with the specified name
    
    java.lang.NullPointerException - if the argument is null
  - getHashFunction
```
public HashProvider.HashFunction getHashFunction()
```

Enum HashProvider.HashMethod

Enum Constant Summary

Method Summary

Methods inherited from class java.lang.Enum

Methods inherited from class java.lang.Object

Enum Constant Detail

RNG

CarterWegman

CRC32

Adler32

Murmur2

Murmur3

Murmur3KirschMitzenmacher

FNVWithLCG

MD2

MD5

SHA1

SHA256

SHA384

SHA512

Method Detail

values

valueOf

getHashFunction