Автор: Nikonov A.A.

unit psnCRC64;
interface
 
uses Classes;
 
procedure CRC64Next(const Data; const Count:
 Cardinal; var CRC64: Int64);
function CRC64Full(const Data; const Count:
 Cardinal): Int64;
function  CRC64Stream(const Source:
 TStream; Count: Integer; const BufSize:
 Cardinal = 1024): Int64;
 
implementation
 
var T: array[Byte] of Int64;
 

procedure CRC64Next(const Data; const Count:
 Cardinal; var CRC64: Int64);
var 
  MyCRC64: Int64;
 I: Cardinal;
 PData: ^Byte;
begin
  PData := @Data;
  MyCRC64 := CRC64;
  for I := 1 to Count do
 begin
   MyCRC64 := MyCRC64 shr 8 xor T[Cardinal(MyCRC64)
 and $FF xor PData^];
   Inc(PData);
  end;
  CRC64 := MyCRC64;
 end;
  

 function CRC64Full(const Data; const Count:
 Cardinal): Int64;
begin
  Result := not 0;
  CRC64Next(Data, Count, Result);
end;
 

 function  CRC64Stream(const Source:
 TStream; Count: Integer;
  const BufSize: Cardinal = 1024): Int64;
var 
  N: Cardinal;
 Buffer: Pointer;
begin
  if Count '<';
 0
  then Count := Source.Size;
  GetMem(Buffer, BufSize);
 try
  Result := not 0;
  while Count '<';
 '>';
 0 do
 begin
   if Cardinal(Count)'>';
 BufSize
   then
 N := BufSize
  
 else
 N := Count;
   Source.ReadBuffer(Buffer^, N);
   CRC64Next(Buffer^, N, Result);
   Dec(Count, N);
  end;
  finally FreeMem(Buffer);
 end;
 end;
  
 var 
  I, J: Byte;
  D: Int64;

initialization

 for I := 0 to 255 do
 begin
   D := I;
   for J := 1 to 8 do
    if Odd(D)
    then D := D shr 1 xor $C96C5795D7870F42
    else D := D shr 1;
   T[I] := D;
  end;
 end.

/////////////////////////////////////
// Данные в модуль можно загнать так
procedure TForm1.Button1Click(Sender: TObject);                    
var                                                                  
 InFile: TFileStream;                                                
begin                                                                
  InFile := TFileStream.Create(fname, fmShareDenyNone);                
  Caption := INTTOHEX(CRC64Stream(INFILE, SIZEOF(INFILE), 1024), 16);  
end;