(Delphi DLL) Compressing StringBuilder Data Using CompressSb (Single Call and Chunked)

See more Compression Examples

1. Single-call compression, where the entire input is compressed in one operation.
2. Chunked compression, where the input is split into multiple parts and processed sequentially using the FirstChunk and LastChunk properties.

The example shows how compressed output is appended to a BinData object, and how the result can be verified by decompressing back to the original text. This is useful for both simple use cases and scenarios where data is processed incrementally (such as streaming or large inputs).

Key Points

• CompressSb converts text to bytes using the Charset property (UTF-8 recommended).
• Compressed data is appended to a BinData object.
• When both FirstChunk and LastChunk are true, compression is done in a single call.
• For chunked processing:
  • First chunk → FirstChunk = true, LastChunk = false
  • Middle chunks → both false
  • Final chunk → LastChunk = true
• Chunked compression is useful when processing data incrementally.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, StringBuilder, BinData, Compression;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
compress: HCkCompression;
sb: HCkStringBuilder;
bdCompressed: HCkBinData;
compressedBase64: PWideChar;
bdChunkedOut: HCkBinData;
sbPart: HCkStringBuilder;
chunkedBase64: PWideChar;
sbDecompressed: HCkStringBuilder;

begin
success := False;

// This example assumes the Chilkat API has already been unlocked.
// See Global Unlock Sample for sample code.

compress := CkCompression_Create();
CkCompression_putAlgorithm(compress,'zlib');

// ================================================================
// 1) Single-call compression (entire data in one call)
// ================================================================

sb := CkStringBuilder_Create();
CkStringBuilder_Append(sb,'The quick brown fox jumps over the lazy dog. ');
CkStringBuilder_Append(sb,'This is a simple example using CompressSb.');

bdCompressed := CkBinData_Create();

// When both FirstChunk and LastChunk are true (the defaults),
// the entire compression happens in a single call.
CkCompression_putFirstChunk(compress,True);
CkCompression_putLastChunk(compress,True);

success := CkCompression_CompressSb(compress,sb,bdCompressed);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

compressedBase64 := CkBinData__getEncoded(bdCompressed,'base64');

Memo1.Lines.Add('Single-call compressed (base64):');
Memo1.Lines.Add(compressedBase64);

// ================================================================
// 2) Chunked compression using FirstChunk / LastChunk
// ================================================================

bdChunkedOut := CkBinData_Create();

// First chunk
CkCompression_putFirstChunk(compress,True);
CkCompression_putLastChunk(compress,False);

sbPart := CkStringBuilder_Create();
CkStringBuilder_Append(sbPart,'The quick brown fox ');

success := CkCompression_CompressSb(compress,sbPart,bdChunkedOut);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

// Middle chunk
CkCompression_putFirstChunk(compress,False);
CkCompression_putLastChunk(compress,False);

CkStringBuilder_Clear(sbPart);
CkStringBuilder_Append(sbPart,'jumps over the lazy dog. ');

success := CkCompression_CompressSb(compress,sbPart,bdChunkedOut);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

// Final chunk
CkCompression_putFirstChunk(compress,False);
CkCompression_putLastChunk(compress,True);

CkStringBuilder_Clear(sbPart);
CkStringBuilder_Append(sbPart,'This is a chunked CompressSb example.');

success := CkCompression_CompressSb(compress,sbPart,bdChunkedOut);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

chunkedBase64 := CkBinData__getEncoded(bdChunkedOut,'base64');

Memo1.Lines.Add('Chunked compressed (base64):');
Memo1.Lines.Add(chunkedBase64);

// ================================================================
// 3) Decompress to verify correctness
// ================================================================

sbDecompressed := CkStringBuilder_Create();

// Decompress in a single call (entire data already assembled)
CkCompression_putFirstChunk(compress,True);
CkCompression_putLastChunk(compress,True);

success := CkCompression_DecompressSb(compress,bdChunkedOut,sbDecompressed);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

Memo1.Lines.Add('Decompressed text:');
Memo1.Lines.Add(CkStringBuilder__getAsString(sbDecompressed));

CkCompression_Dispose(compress);
CkStringBuilder_Dispose(sb);
CkBinData_Dispose(bdCompressed);
CkBinData_Dispose(bdChunkedOut);
CkStringBuilder_Dispose(sbPart);
CkStringBuilder_Dispose(sbDecompressed);

end;