Difference between revisions of "FNV"

Latest revision as of 11:14, 24 August 2009

FNV hash function

[edit] Overview

The Fowler-Noll-Vo hash function is used in various Sims 3 resources, be it the 32 or 64 bit form, it is used in the generation of property ids, instance ids, bone ids, etc. Occasionally a 24 bit hash will be used, which is just a 32 bit hash with the high byte folded down and XORd with the low byte.

[edit] Formula

The hash is generated with an initial offset, which is multiplied by a prime number and XOR'ed by each byte of data.

N.B. When hashing strings, the characters must first be converted to lower-case to comply with standards.

FNV(byte[] data)
{
	hash = offset;
	foreach(byte b in data)
	{
		hash *= prime;
		hash ^= b;
	}
	return hash;
}

[edit] Constants