MurMurHash64B in Pascal

MurMur.pas

unit MurMur;
interface

function MurmurHash64B(s: PAnsiChar; Len: Integer; Seed: UInt32) : UInt64;

implementation

function MurmurHash64B(s: PAnsiChar; Len: Integer; Seed: UInt32) : UInt64;
const
    m = $5bd1e995;
    r = 24;
var
    h1, h2, k1, k2, c: UInt32;
    data: PUInt32;
begin
    h1 := Seed Xor Len;
    h2 := 0;
    data := PUInt32(s);
    while Len >= 8 do
    begin
        k1 := data^;
        Inc(data);
        k1 := k1 * m;
        k1 :=  (k1 Xor (k1 Shr r)) * m;
        h1 := (h1 * m) Xor k1;
        Len := Len - 4;

        k2 := data^;
        Inc(data);
        k2 := k2 * m;
        k2 := (k2 Xor (k2 Shr r)) * m;
        h2 := (h2 * m) Xor k2;
        Len := Len - 4;
    end;

    if Len >= 4 then
    begin
        k1 := data^;
        Inc(data);
        k1 := k1 * m;
        k1 := (k1 Xor (k1 Shr r)) * m;
        h1 := (h1 * m) Xor k1;
        Len := Len - 4;
    end;

    if Len > 0 then
    begin
        if Len > 1 then
        begin
            if Len > 2 then
            begin
                c := UInt32((PAnsiChar(data))[2]);
                h2 := h2 Xor (c Shl 16)  
            end;
            c := UInt32((PAnsiChar(data))[1]);
            h2 := h2 Xor (c Shl 8)  
        end;
        h2 := h2 Xor UInt32((PAnsiChar(data))^);
        h2 := h2 * m;
    end;

    h1 := (h1 Xor(h2 Shr 18)) * m;
    h2 := (h2 Xor (h1 Shr 22)) * m;
    h1 := (h1 Xor (h2 Shr 17)) * m;
    h2 := (h2 Xor (h1 Shr 19)) * m;

    Result := h1;
    Result := (Result Shl 32) Or h2;
end;
end.

Tested on Free Pascal and Delphi.