Pascal (Lazarus/Delphi)

SFTP Upload Large File in Parts

See more SFTP Examples

Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.FileAccess,
  Chilkat.BinData,
  Chilkat.SFtp;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  sftp: TSFtp;
  hostname: string;
  port: Integer;
  handle: string;
  localFilePath: string;
  fac: TFileAccess;
  blockSize: Integer;
  numBlocks: Integer;
  bd: TBinData;
  i: Integer;

begin
  success := False;

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

  sftp := TSFtp.Create;

  //  Set some timeouts, in milliseconds:
  sftp.ConnectTimeoutMs := 5000;
  sftp.IdleTimeoutMs := 10000;

  //  Connect to the SSH server.  
  //  The standard SSH port = 22
  //  The hostname may be a hostname or IP address.
  hostname := 'sftp.example.com';
  port := 22;
  success := sftp.Connect(hostname,port);
  if (success <> True) then
    begin
      WriteLn(sftp.LastErrorText);
      Exit;
    end;

  //  Authenticate with the SSH server.  Chilkat SFTP supports
  //  both password-based authenication as well as public-key
  //  authentication.  This example uses password authenication.
  success := sftp.AuthenticatePw('myLogin','myPassword');
  if (success <> True) then
    begin
      WriteLn(sftp.LastErrorText);
      Exit;
    end;

  //  After authenticating, the SFTP subsystem must be initialized:
  success := sftp.InitializeSftp();
  if (success <> True) then
    begin
      WriteLn(sftp.LastErrorText);
      Exit;
    end;

  //  Open a remote file for writing on the SSH server.
  //  If the file already exists, it is overwritten.
  //  (Specify "createNew" instead of "createTruncate" to
  //  prevent overwriting existing files.)
  handle := sftp.OpenFile('big.zip','writeOnly','createTruncate');
  if (sftp.LastMethodSuccess <> True) then
    begin
      WriteLn(sftp.LastErrorText);
      Exit;
    end;

  //  We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
  //  to the SFTP server.
  localFilePath := 'qa_data/zips/big.zip';

  //  Rather than uploading in one shot, we'll read the local file in chunks
  //  and upload a chunk at a time.
  fac := TFileAccess.Create;

  success := fac.OpenForRead(localFilePath);
  if (success = False) then
    begin
      sftp.CloseHandle(handle);
      WriteLn(fac.LastErrorText);
      Exit;
    end;

  //  If we were to split the local file into 128K chunks, how many chunks (blocks) would
  //  we have, including the last partial block?
  blockSize := 131072;
  numBlocks := fac.GetNumBlocks(blockSize);
  WriteLn('Number of blocks = ' + numBlocks);

  bd := TBinData.Create;
  i := 0;
  while i < numBlocks do
    begin
      //  Read the Nth block, which gets appended to the bd.  (which means
      //  we must clear the contents of bd before the next iteration)
      success := fac.ReadBlockBd(i,blockSize,bd);
      if (success = False) then
        begin
          sftp.CloseHandle(handle);
          WriteLn(fac.LastErrorText);
          Exit;
        end;

      //  Upload this block to the open remote file.
      success := sftp.WriteFileBd(handle,bd);
      if (success = False) then
        begin
          WriteLn(sftp.LastErrorText);
          Exit;
        end;

      //  Clear the contents for the next iteration.
      bd.Clear();

      i := i + 1;
    end;

  //  Close the local file.
  fac.FileClose();

  //  -----------------------------------------------------------------------------
  //  This is important.  You must close the handle on the server.
  //  Otherwise open handles will accumulate on the server until eventually a limit
  //  is reached and the server will fail on a call to OpenFile.
  //  -----------------------------------------------------------------------------

  //  Close the remote file handle on the server.
  success := sftp.CloseHandle(handle);
  if (success <> True) then
    begin
      WriteLn(sftp.LastErrorText);
      Exit;
    end;

  WriteLn('Success.');


  sftp.Free;
  fac.Free;
  bd.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.