Delphi ActiveX

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. Delphi ActiveX

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
success: Integer;
facSrc: TCkFileAccess;
facDest: TCkFileAccess;
blockSize: Integer;
numBlocks: Integer;
compress: TChilkatCompression;
decompressedBytes: Array of Byte;
compressedBytes: Array of Byte;
i: Integer;

begin
success := 0;

// 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('c:/temp/qa_output/compressedBmp.dat');
if (success = 0) 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('c:/temp/qa_output/decompressed.bmp');
if (success = 0) then
  begin
    Memo1.Lines.Add(facDest.LastErrorText);
    Exit;
  end;

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

// Assuming numBlocks > 1
compress.FirstChunk := 1;
compress.LastChunk := 0;

i := 0;
while i < numBlocks do
  begin
    compressedBytes := facSrc.ReadBlock(i,blockSize);

    decompressedBytes := compress.DecompressBytes(compressedBytes);
    facDest.FileWrite(decompressedBytes);

    i := i + 1;

    compress.FirstChunk := 0;
    if (i = (numBlocks - 1)) then
      begin
        compress.LastChunk := 1;
      end;
  end;

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

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