Delphi ActiveX

Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties. 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;
fileBytes: Array of Byte;
compressedBytes: Array of Byte;
i: Integer;

begin
success := 0;

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

// Open a large binary file for reading.
success := facSrc.OpenForRead('qa_data/bmp/big.bmp');
if (success = 0) then
  begin
    Memo1.Lines.Add(facSrc.LastErrorText);
    Exit;
  end;

// If we compress in 64K chunks, find out how many blocks there will be.
blockSize := 65536;
numBlocks := facSrc.GetNumBlocks(blockSize);

// Open an output file for the compressed data.
success := facDest.OpenForWrite('c:/temp/qa_output/compressedBmp.dat');
if (success = 0) then
  begin
    Memo1.Lines.Add(facDest.LastErrorText);
    Exit;
  end;

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

// ----------------------------------------------------------------------------------
// This is the deprecated way of compressing in chunks using Begin/More/End methods..
// ----------------------------------------------------------------------------------
i := 0;
while i < numBlocks do
  begin
    fileBytes := facSrc.ReadBlock(i,blockSize);
    if (i = 0) then
      begin
        compressedBytes := compress.BeginCompressBytes(fileBytes);
      end
    else
      begin
        compressedBytes := compress.MoreCompressBytes(fileBytes);
      end;

    facDest.FileWrite(compressedBytes);

    i := i + 1;
  end;

// At the very end, flush any remaining compressed bytes, if any.
compressedBytes := compress.EndCompressBytes();
facDest.FileWrite(compressedBytes);

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

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

// ----------------------------------------------------------------------------------
// This is new way of compressing in chunks using FirstChunk and LastChunk properties
// ----------------------------------------------------------------------------------

success := facSrc.OpenForRead('qa_data/bmp/big.bmp');
if (success = 0) then
  begin
    Memo1.Lines.Add(facSrc.LastErrorText);
    Exit;
  end;

success := facDest.OpenForWrite('c:/temp/qa_output/compressedBmp2.dat');
if (success = 0) then
  begin
    Memo1.Lines.Add(facDest.LastErrorText);
    Exit;
  end;

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

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

    facDest.FileWrite(compressedBytes);

    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 compressing file 2.');
end;