Pascal (Lazarus/Delphi)

Compress and Decompress Hex String

See more Compression Examples

Imagine we have data represented as a hex string. This example demonstrates how to decode, compress, and re-encode to a smaller hex string representing the compressed data. An even better choice is to re-encode to a more compact encoding such as base64.

Note: This example requires Chilkat v9.5.0.66 or greater.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.BinData,
  Chilkat.Compression;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  strHex: string;
  compress: TCompression;
  binDat: TBinData;
  compressedHex: string;
  compressedBase64: string;
  decompressedHex: string;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  strHex := '54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A';

  compress := TCompression.Create;
  compress.Algorithm := 'deflate';

  binDat := TBinData.Create;
  //  Load the hex string into a BinData object.
  //  This decodes the hexidecimal. The decoded bytes will be contained in the BinData.
  binDat.AppendEncoded(strHex,'hex');

  //  Compress the BinData.
  compress.CompressBd(binDat);

  //  Get the compressed data in hex format:
  compressedHex := binDat.GetEncoded('hex');
  WriteLn('compressed hex:');
  WriteLn(compressedHex);

  //  The compressed hex is: 0BC94855282CCD4CCE56482ACA2FCF5348CBAF50C82ACD2D484D51C82F4B2D522801CAE72456552AA4E4A7EBF172850C61E5BC5C00

  //  Even better, get the compressed data in base64 format:
  //  (base64url and modbase64 are other valid choices...)
  compressedBase64 := binDat.GetEncoded('base64');
  WriteLn('compressed base64:');
  WriteLn(compressedBase64);

  //  The compressed base64 is: C8lIVSgszUzOVkgqyi/PU0jLr1DIKs0tSE1RyC9LLVIoAcrnJFZVKqTkp+vxcoUMYeW8XAA=

  //  Now decompress:
  binDat.Clear();
  binDat.AppendEncoded(compressedHex,'hex');
  compress.DecompressBd(binDat);

  decompressedHex := binDat.GetEncoded('hex');
  WriteLn('decompressed hex:');
  WriteLn(decompressedHex);

  //  The output is the original hex string:
  //  54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A


  compress.Free;
  binDat.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.