(Delphi DLL) 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 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, FileAccess, CkByteData, Compression;

...

procedure TForm1.Button1Click(Sender: TObject);
var
facSrc: HCkFileAccess;
facDest: HCkFileAccess;
success: Boolean;
blockSize: Integer;
numBlocks: Integer;
compress: HCkCompression;
decompressedBytes: HCkByteData;
compressedBytes: HCkByteData;
i: Integer;

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

facSrc := CkFileAccess_Create();
facDest := CkFileAccess_Create();

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

success := CkFileAccess_OpenForRead(facSrc,'qa_data/bmp/compressedBmp.dat');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkFileAccess__lastErrorText(facSrc));
    Exit;
  end;

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

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

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

decompressedBytes := CkByteData_Create();
compressedBytes := CkByteData_Create();

i := 0;
while i < numBlocks do
  begin
    success := CkFileAccess_ReadBlock(facSrc,i,blockSize,compressedBytes);
    if (i = 0) then
      begin
        success := CkCompression_BeginDecompressBytes(compress,compressedBytes,decompressedBytes);
      end
    else
      begin
        success := CkCompression_MoreDecompressBytes(compress,compressedBytes,decompressedBytes);
      end;

    CkFileAccess_FileWrite(facDest,decompressedBytes);

    i := i + 1;
  end;

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

CkFileAccess_FileClose(facSrc);
CkFileAccess_FileClose(facDest);

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

CkFileAccess_Dispose(facSrc);
CkFileAccess_Dispose(facDest);
CkCompression_Dispose(compress);
CkByteData_Dispose(decompressedBytes);
CkByteData_Dispose(compressedBytes);

end;