Delphi DLL

Check Whether the Last SFTP Read Failed

Demonstrates the Chilkat SFtp.LastReadFailed method, which returns whether the most recent read for a handle failed. The only argument is the handle. A normal end-of-file is not a failure.

Background: A chunked read loop needs to tell three outcomes apart: more data, a clean end-of-file, and an actual error such as a dropped connection or a revoked handle. LastReadFailed isolates the error case — it is false on a normal EOF read (which succeeds with zero bytes) and true for an empty, malformed, or already-closed handle — so the loop can stop cleanly on EOF but bail out with an error message on a genuine failure.

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var
success: Boolean;
sftp: HCkSFtp;
port: Integer;
password: PWideChar;
handle: PWideChar;
reading: Boolean;
chunkSize: Integer;
bd: HCkBinData;

begin
success := False;

//  Demonstrates the SFtp.LastReadFailed method, which returns whether the most recent read for a
//  handle failed.  The only argument is the handle.  A normal end-of-file is NOT a failure.

sftp := CkSFtp_Create();

//  Connect, authenticate, and initialize the SFTP subsystem.
port := 22;
success := CkSFtp_Connect(sftp,'sftp.example.com',port);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
password := 'mySshPassword';

success := CkSFtp_AuthenticatePw(sftp,'mySshLogin',password);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

success := CkSFtp_InitializeSftp(sftp);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

handle := CkSFtp__openFile(sftp,'subdir/data.txt','readOnly','openExisting');
if (CkSFtp_getLastMethodSuccess(sftp) = False) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

reading := True;
chunkSize := 4096;
bd := CkBinData_Create();
while reading do
  begin
    success := CkSFtp_ReadFileBd(sftp,handle,chunkSize,bd);

    //  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
    //  zero bytes, and LastReadFailed is 0.
    if (CkSFtp_LastReadFailed(sftp,handle)) then
      begin
        Memo1.Lines.Add('Read failed: ' + CkSFtp__lastErrorText(sftp));
        Exit;
      end;

    reading := not CkSFtp_Eof(sftp,handle);
  end;

success := CkSFtp_CloseHandle(sftp,handle);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;
Memo1.Lines.Add('Read ' + IntToStr(CkBinData_getNumBytes(bd)) + ' bytes with no read failures.');

CkSFtp_Disconnect(sftp);

CkSFtp_Dispose(sftp);
CkBinData_Dispose(bd);