Brian Dunning's FileMaker Custom Functions

HashFNV1a32 ( text ; empty )

Computes the 32 bit binary FNV-1a has for the input text.

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Vaughan Bromfield   Vaughan Bromfield

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  Sample input:
HashFNV1a32 ( "contracts" ; "" )
  Sample output:
01011001111001011000000111111111

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

HashFNV1a32 ( text ; empty )
The initial value for "empty" must be empty ("")

This function computes the 32-bit binary hash for the input text based on the FNV-1a algorithm

This function requires the following functions:
Bin2dec ( bin ; empty )
Dec2bin ( decimalNumber ; empty )
XORbin ( bin0 ; bin1 ; empty )

This custom function was written by Vaughan Bromfield on 14 March 2010.

This function is based on the algorithm published at:
http://www.isthe.com/chongo/tech/comp/fnv/index.html
http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash

 

Comments

Vaughan Bromfield   Vaughan Bromfield
Aug 26, 2010
Here is an updated version of the function that uses a local variable instead of the second parameter. It should AFAIK produce the same results.


------

// HashFNV1a32 ( text )
//
// This function computes the 32-bit binary hash
// for the input text based on the FNV-1a algorithm
//
// This function requires the following functions:
// Bin2dec()
// Dec2bin()
// XORbin()
//
// This custom function was written by Vaughan Bromfield
// vbromfield@optusnet.com.au
// 14 March 2010
//
// This function is based on the algorithm published at:
// http://www.isthe.com/chongo/tech/comp/fnv/index.html
// http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash
//
// The local $variable is used to carry the result to the next recursion instead of a function parameter.


Case (

Length( text ) = 0 ;
Let( [ result = $_hash_HashFNV1a32 ; $_hash_HashFNV1a32 = "" ] ; result ) ; // return result, clear local variables

Let(
[
offset = 2166136261 ;
prime = 16777619 ;
chr = Right ( text ; 1 ) ;
nextxt = Left ( text ; Length( text ) - 1 ) ;
hash0 = If( IsEmpty( $_hash_HashFNV1a32 ) ; Dec2Bin( offset ) ; $_hash_HashFNV1a32 ) ;
hash1 = XORbin( hash0 ; Dec2Bin( Code( chr ) ) ) ;
$_hash_HashFNV1a32 = Right( "00000000000000000000000000000000" & Dec2Bin( Mod( Bin2Dec( hash1 ) * prime ; 4294967296 ) ) ; 32 )
] ;

HashFNV1a32 ( nextxt ) // recurse

) //end let

) //end case

------
 
P Sanchez   P Sanchez, Jacksonville, FL
May 13, 2011
Do you have a CF for the unencryption of this?

Thanks!
 
P Sanchez   P Sanchez, Jacksonville, FL
May 13, 2011
sorry, decrypt...
 
Vaughan   Vaughan, Sydney, Australia
May 14, 2011
This is a hash function. There is no way to "decrypt" a hash function. Hash functions are not reversible.
 

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