Algorithm of CRC32 calculation for file

If you need calculate a CRC32 for some file or some string, then you must do:
1. build a CRC table
2. calculate a CRC for each line of your file
3. calculate a total CRC
1. CRC table creation:

typeLong = recordLoWord: Word;
    HiWord: Word;
  end;

constCRCPOLY = $EDB88320;

varCRCTable: array[0..512] OfLongint;

procedureBuildCRCTable;
vari, j: Word;
  r: Longint;
beginFillChar(CRCTable, SizeOf(CRCTable), 0);
  fori := 0 to255 do

  beginr := i shl1;
    forj := 8 downto0 do

      if(r and1) <> 0 thenr := (r Shr1) xorCRCPOLY
      elser := r shr1;
    CRCTable[i] := r;
   end;
end;

2. CRC calculation for file:

functionRecountCRC(b: byte; CrcOld: Longint): Longint;
beginRecountCRC := CRCTable[byte(CrcOld xorLongint(b))] xor((CrcOld shr8) and$00FFFFFF)
end;

functionHextW(w: Word): string;
consth: array[0..15] Ofchar = '0123456789ABCDEF';
beginHextW := '';
  HextW := h[Hi(w) shr4] + h[Hi(w) and$F] + h[Lo(w) shr4]+h[Lo(w) and$F];
end;

functionHextL(l: Longint): string;
begin

  withLong(l) doHextL := HextW(HiWord) + HextW(LoWord);
end;

functionGetCRC32(FileName: string): string;
varBuffer: PChar;
  f: File ofByte;
  b: array[0..255] ofByte;
  CRC: Longint;
  e, i: Integer;
beginBuildCRCTable;
  CRC := $FFFFFFFF;
  AssignFile(F, FileName);
  FileMode := 0;
  Reset(F);
  GetMem(Buffer, SizeOf(B));
  repeatFillChar(b, SizeOf(b), 0);
    BlockRead(F, b, SizeOf(b), e);
    fori := 0 to(e-1) doCRC := RecountCRC(b[i], CRC);
  until(e < 255) or(IOresult <> 0);
  FreeMem(Buffer, SizeOf(B));
  CloseFile(F);
  CRC := NotCRC;
  Result := '$' + HextL(CRC);
end;

[From]Delphi tip#48: CRC32 calculation