(*

 * Hedgewars, a worms-like game

 * Copyright (c) 2004-2006 Andrey Korotaev <unC0Rr@gmail.com>

 *

 *

 *

 *)

unit uRandom;

interface

{$INCLUDE options.inc}

procedure SetRandomSeed(Seed: shortstring);

function  GetRandom: Double; overload;

function  GetRandom(m: LongWord): LongWord; overload;

implementation

var cirbuf: array[0..63] of Longword;

    n: byte = 54;

function GetNext: Longword;

begin

n:= (n + 1) and $3F;

cirbuf[n]:=

           (cirbuf[(n + 40) and $3F] +           {n - 24 mod 64}

            cirbuf[(n +  9) and $3F])            {n - 55 mod 64}

            and $7FFFFFFF;                       {mod 2^31}

Result:= cirbuf[n]

end;

procedure SetRandomSeed(Seed: shortstring);

var i: Longword;

begin

n:= 54;

if Length(Seed) > 54 then Seed:= copy(Seed, 1, 54); // not 55 to ensure we have odd numbers in cirbuf

for i:= 0 to pred(Length(Seed)) do

    cirbuf[i]:= byte(Seed[i + 1]) * (i + 1);

for i:= Length(Seed) to 54 do

    cirbuf[i]:= i * 7 + 1;

for i:= 0 to 1023 do GetNext

end;

function GetRandom: Double;

begin

Result:= frac( GetNext * 0.00073 + GetNext * 0.00301)

end;

function GetRandom(m: LongWord): LongWord;

begin

GetNext;

Result:= GetNext mod m

end;

end.