Editing WoW:USERAPI StringHash

{{userfunc}} <!-- Leave this line in! -->
<center>'''StringHash''' ''- by {{user|Mikk}} -''</center>


Return a fair-quality 32-bit hash of a string

 hashVal = StringHash("string")


== Example ==
 > print(StringHash(""))
 1 
 > print(StringHash("ab"))
 3458343178
 > print(StringHash("ba"))
 3466747145
 > print(StringHash("AB"))
 2653593770
 > print(StringHash("BA"))
 2661997737
 > print(StringHash("The quick brown fox jumps over the lazy dog"))
 3402772626

==Details==

* This algorithm is ~30% faster than a Lua implementation of the Java [http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html#hashCode() String.hashCode] library call

* The bit transmutation patterns and resulting collision rates are MUCH better than the results from the Java hash

* See [[StringHash/Analysis]]

==Code==
 local function StringHash(text)
   local counter = 1
   local len = string.len(text)
   for i = 1, len, 3 do 
     counter = math.fmod(counter*8161, 4294967279) +  -- 2^32 - 17: Prime!
   	  (string.byte(text,i)*16776193) +
   	  ((string.byte(text,i+1) or (len-i+256))*8372226) +
   	  ((string.byte(text,i+2) or (len-i+256))*3932164)
   end
   return math.fmod(counter, 4294967291) -- 2^32 - 5: Prime (and different from the prime in the loop)
 end


__NOTOC__
[[Category:User defined functions]]