Update form Ansii to Unicode

[WojTec]

Original function in C++:

Code:

unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed )
{
   // 'm' and 'r' are mixing constants generated offline.
   // They're not really 'magic', they just happen to work well.

   const unsigned int m = 0x5bd1e995;
   const int r = 24;

   // Initialize the hash to a 'random' value

   unsigned int h = seed ^ len;

   // Mix 4 bytes at a time into the hash

   const unsigned char * data = (const unsigned char *)key;

   while(len >= 4)
   {
      unsigned int k = *(unsigned int *)data;

      k *= m; 
      k ^= k >> r; 
      k *= m; 
      
      h *= m; 
      h ^= k;

      data += 4;
      len -= 4;
   }
   
   // Handle the last few bytes of the input array

   switch(len)
   {
   case 3: h ^= data[2] << 16;
   case 2: h ^= data[1] << 8;
   case 1: h ^= data[0];
           h *= m;
   };

   // Do a few final mixes of the hash to ensure the last few
   // bytes are well-incorporated.

   h ^= h >> 13;
   h *= m;
   h ^= h >> 15;

   return h;
}

Translation for Delphi Ansii version:

Delphi-Quellcode:

function Murmur2(const S: AnsiString; const Seed: Cardinal = $9747b28c): Cardinal;
const
  // 'm' and 'r' are mixing constants generated offline.
  // They're not really 'magic', they just happen to work well.
  m = $5bd1e995;
  r = 24;
var
  hash: LongWord;
  len: LongWord;
  k: LongWord;
  data: Integer;
begin
  len := Length(S);

  //The default seed, $9747b28c, is from the original C library

  // Initialize the hash to a 'random' value
  hash := seed xor len;

  // Mix 4 bytes at a time into the hash
  data := 1;

  while(len >= 4) do
  begin
      k := PLongWord(@S[data])^;

      k := k*m;
      k := k xor (k shr r);
      k := k*m;

      hash := hash*m;
      hash := hash xor k;

      data := data+4;
      len := len-4;
  end;

  {   Handle the last few bytes of the input
          S: ... $69 $18 $2f
  }
  Assert(len <= 3);
  if len = 3 then
      hash := hash xor (LongWord(s[data+2]) shl 16);
  if len >= 2 then
      hash := hash xor (LongWord(s[data+1]) shl 8);
  if len >= 1 then
  begin
      hash := hash xor (LongWord(s[data]));
      hash := hash * m;
  end;

  // Do a few final mixes of the hash to ensure the last few
  // bytes are well-incorporated.
  hash := hash xor (hash shr 13);
  hash := hash * m;
  hash := hash xor (hash shr 15);

  Result := hash;
end;

I don't like AnsiString, so I'm trying to change to string:

function Murmur2(const AValue: string; const Seed: Cardinal = $9747b28c): Cardinal;

Result is different than in Ansii version. I think problem is here:

k := PLongWord(@AValue[data])^;

How to fix it?

Also line:

data := 1;

is valid?