HashFunctionUtil (Cognitive Foundry)

java.lang.Object
- gov.sandia.cognition.hash.HashFunctionUtil

```
public class HashFunctionUtil
extends java.lang.Object
```
Static class with helper functions for hash codes

Since:

3.4.2

Author:

Kevin R. Dixon

Constructor Summary

Constructors
Constructor and Description

HashFunctionUtil()

Constructors
Constructor and Description
`HashFunctionUtil()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static byte[]`	`combineHash(HashFunction hash, boolean ordered, byte[]... inputs)` Cascades the hash codes
`static byte[]`	`fromHexString(java.lang.String hexString)` Converts the hex-string back into an array of bytes
`static boolean`	`isPrime(long num)` Determines if a number is prime or not
`static long`	`nextPrime(long num)` Returns the next-greater prime, sort of like "ceil" but for primes.
`static byte[]`	`salt(HashFunction hash, byte[]... inputs)` Computes the salted hash of the given inputs, that is, we concatenate the inputs together and compute the hash of the concatenated bytes.
`static void`	`saltInto(byte[] output, HashFunction hash, byte[]... inputs)` Computes the salted hash of the given inputs, that is, we concatenate the inputs together and compute the hash of the concatenated bytes.
`static byte[]`	`toByteArray(int value)` Converts an int into a 4-byte array in Big Endian order (most-significant byte in slot 0)
`static void`	`toByteArray(int value, byte[] output)` Converts an int into a 4-byte array in Big Endian order (most-significant byte in slot 0)
`static byte[]`	`toByteArray(long value)` Converts a long into an 8-byte array in Big Endian order (most-significant byte in slot 0)
`static void`	`toByteArray(long value, byte[] output)` Converts a long into an 8-byte array in Big Endian order (most-significant byte in slot 0)
`static java.lang.String`	`toHexString(byte[] bytes)` Converts a byte array to a lower-case Hex string
`static java.lang.String`	`toHexString(int input)` Converts the given int to a Big Endian hex string
`static java.lang.String`	`toHexString(long input)` Converts the given long to a Big Endian hex string
`static int`	`toInteger(byte[] data)` Converts the 4-byte array to a Big Endian int.
`static int`	`toInteger(byte[] data, int offset)` Converts the 4 bytes in the given array starting at "offset" to a Big Endian int.
`static long`	`toLong(byte[] data)` Converts the 8-byte value to a Big Endian long
`static long`	`toLong(byte[] data, int offset)` Converts the 8-byte value at "offset" to a Big Endian long
`static byte`	`valueOf(char hexChar)` Returns the hex value of the given character

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

- Constructor Detail
  - HashFunctionUtil
```
public HashFunctionUtil()
```
- Method Detail
  - toByteArray
```
public static byte[] toByteArray(int value)
```
    Converts an int into a 4-byte array in Big Endian order (most-significant byte in slot 0)
    
    Parameters:
    
    value - Integer to convert
    
    Returns:
    
    4-byte array in Big Endian order (most-significant byte in slot 0)
  - toByteArray
```
public static void toByteArray(int value,
                               byte[] output)
```
    Converts an int into a 4-byte array in Big Endian order (most-significant byte in slot 0)
    
    Parameters:
    
    value - Integer to convert
    
    output - 4-byte array to store the int
  - toByteArray
```
public static byte[] toByteArray(long value)
```
    Converts a long into an 8-byte array in Big Endian order (most-significant byte in slot 0)
    
    Parameters:
    
    value - long to convert
    
    Returns:
    
    8-byte array to store the long
  - toByteArray
```
public static void toByteArray(long value,
                               byte[] output)
```
    Converts a long into an 8-byte array in Big Endian order (most-significant byte in slot 0)
    
    Parameters:
    
    value - long to convert
    
    output - 8-byte array to store the long
  - combineHash
```
public static byte[] combineHash(HashFunction hash,
                                 boolean ordered,
                                 byte[]... inputs)
```
    Cascades the hash codes
    
    Parameters:
    
    hash - HashFunction used to compute the results
    
    ordered - true for ordered hash, false for unordered
    
    inputs - Inputs to compute the hash of
    
    Returns:
    
    Cascaded hash function of the inputs
  - salt
```
public static byte[] salt(HashFunction hash,
                          byte[]... inputs)
```
    Computes the salted hash of the given inputs, that is, we concatenate the inputs together and compute the hash of the concatenated bytes.
    
    Parameters:
    
    hash - HashFunction that computes the hash
    
    inputs - Ordered inputs to the hash function
    
    Returns:
    
    Output into which we place the output (salted hash)
  - saltInto
```
public static void saltInto(byte[] output,
                            HashFunction hash,
                            byte[]... inputs)
```
    Computes the salted hash of the given inputs, that is, we concatenate the inputs together and compute the hash of the concatenated bytes.
    
    Parameters:
    
    output - Output into which we place the output (salted hash)
    
    hash - HashFunction that computes the hash
    
    inputs - Ordered inputs to the hash function
  - toHexString
```
public static java.lang.String toHexString(int input)
```
    Converts the given int to a Big Endian hex string
    
    Parameters:
    
    input - Input to convert
    
    Returns:
    
    hex string (8 chars)
  - toHexString
```
public static java.lang.String toHexString(long input)
```
    Converts the given long to a Big Endian hex string
    
    Parameters:
    
    input - Input to convert
    
    Returns:
    
    hex string (16 chars)
  - toHexString
```
public static java.lang.String toHexString(byte[] bytes)
```
    Converts a byte array to a lower-case Hex string
    
    Parameters:
    
    bytes - byte array to convert
    
    Returns:
    
    String representing the byte array
  - valueOf
```
public static byte valueOf(char hexChar)
```
    Returns the hex value of the given character
    
    Parameters:
    
    hexChar - Hex character, such as '0' or 'A'
    
    Returns:
    
    The value of the hex character.
  - fromHexString
```
public static byte[] fromHexString(java.lang.String hexString)
```
    Converts the hex-string back into an array of bytes
    
    Parameters:
    
    hexString - Hex string, such as "0123456789ABCDEF", where each byte is represented by two characters
    
    Returns:
    
    Byte representation of the hex string, will be half the length of string
  - toInteger
```
public static int toInteger(byte[] data)
```
    Converts the 4-byte array to a Big Endian int.
    
    Parameters:
    
    data - 4-byte array to convert
    
    Returns:
    
    Big Endian int representation of the byte array
  - toInteger
```
public static int toInteger(byte[] data,
                            int offset)
```
    Converts the 4 bytes in the given array starting at "offset" to a Big Endian int.
    
    Parameters:
    
    data - Array to convert
    
    offset - Offset into the array
    
    Returns:
    
    Big Endian int representation of the byte array at offset
  - toLong
```
public static long toLong(byte[] data)
```
    Converts the 8-byte value to a Big Endian long
    
    Parameters:
    
    data - byte array to convert
    
    Returns:
    
    Long of the given byte array
  - toLong
```
public static long toLong(byte[] data,
                          int offset)
```
    Converts the 8-byte value at "offset" to a Big Endian long
    
    Parameters:
    
    data - byte array to convert
    
    offset - Offset into the byte array
    
    Returns:
    
    Long at the given offset
  - isPrime
```
@PublicationReference(author="Snort IDS",
                      title="sfhashfcn.c",
                      type=Misc,
                      year=2012,
                      url="http://www.rajivchakravorty.com/source-code/.tmp/snort-html/sfhashfcn_8c-source.html",
                      notes={"Not an efficient implementation.","My improvements make the algorithm O(sqrt(n/2)), instead of O(n), but it still sucks"})
public static boolean isPrime(long num)
```
    Determines if a number is prime or not
    
    Parameters:
    
    num - Number to determine if it's a prime number or not
    
    Returns:
    
    True if prime, false if not
  - nextPrime
```
@PublicationReference(author="Snort IDS",
                      title="sfhashfcn.c",
                      type=Misc,
                      year=2012,
                      url="http://www.rajivchakravorty.com/source-code/.tmp/snort-html/sfhashfcn_8c-source.html",
                      notes="Not an efficient implementation.")
public static long nextPrime(long num)
```
    Returns the next-greater prime, sort of like "ceil" but for primes.
    
    Parameters:
    
    num - Number to return the next-greater prime number of
    
    Returns:
    
    Prime number such that it is greater than or equal to "num"

Class HashFunctionUtil

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

HashFunctionUtil

Method Detail

toByteArray

toByteArray

toByteArray

toByteArray

combineHash

salt

saltInto

toHexString

toHexString

toHexString

valueOf

fromHexString

toInteger

toInteger

toLong

toLong

isPrime

nextPrime