(Delphi ActiveX) Decompress Large Binary File in Blocks

Decompresses a large binary file in blocks. This example uses BeginDecompressBytes, MoreDecompressBytes, and EndDecompressBytes.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
facSrc: TCkFileAccess;
facDest: TCkFileAccess;
success: Integer;
blockSize: Integer;
numBlocks: Integer;
compress: TChilkatCompression;
decompressedBytes: Array of Byte;
compressedBytes: Array of Byte;
i: Integer;

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

facSrc := TCkFileAccess.Create(Self);
facDest := TCkFileAccess.Create(Self);

// Open a previously compressed file for decompressing.
// See Compress Large File in Blocks

success := facSrc.OpenForRead('qa_data/bmp/compressedBmp.dat');
if (success <> 1) then
  begin
    Memo1.Lines.Add(facSrc.LastErrorText);
    Exit;
  end;

// If we compress in 32K chunks, find out how many blocks there will be.
blockSize := 32768;
numBlocks := facSrc.GetNumBlocks(blockSize);

// Open an output file for the decompressed data.
success := facDest.OpenForWrite('qa_output/decompressed.bmp');
if (success <> 1) then
  begin
    Memo1.Lines.Add(facDest.LastErrorText);
    Exit;
  end;

compress := TChilkatCompression.Create(Self);
compress.Algorithm := 'deflate';

i := 0;
while i < numBlocks do
  begin
    compressedBytes := facSrc.ReadBlock(i,blockSize);
    if (i = 0) then
      begin
        decompressedBytes := compress.BeginDecompressBytes(compressedBytes);
      end
    else
      begin
        decompressedBytes := compress.MoreDecompressBytes(compressedBytes);
      end;

    facDest.FileWrite(decompressedBytes);

    i := i + 1;
  end;

// At the very end, flush any remaining decompressed bytes, if any.
decompressedBytes := compress.EndDecompressBytes();
facDest.FileWrite(decompressedBytes);

facSrc.FileClose();
facDest.FileClose();

Memo1.Lines.Add('Finished decompressing file.');
end;