Issue #515: Handle encoding errors in apphelpers.ReadTextfileChunk ac…

…cording to how Delphi 10.3 raises exceptions. And probably fix the issue by increasing the new chunk size by 1M instead of only 4B.

source/apphelpers.pas

@@ -1338,7 +1338,7 @@ function DetectEncoding(Stream: TStream): TEncoding;
 
 function ReadTextfileChunk(Stream: TFileStream; Encoding: TEncoding; ChunkSize: Int64 = 0): String;
 const
-  BufferPadding = 4;
+  BufferPadding = SIZE_MB;
 var
   DataLeft, StartPosition: Int64;
   LBuffer: TBytes;
@@ -1356,24 +1356,22 @@ function ReadTextfileChunk(Stream: TFileStream; Encoding: TEncoding; ChunkSize:
     ChunkSize := DataLeft;
 
   i := 0;
-  while Length(LBuffer) = 0 do begin
-    SetLength(LBuffer, ChunkSize);
-    Stream.ReadBuffer(Pointer(LBuffer)^, ChunkSize);
-    LBuffer := Encoding.Convert(Encoding, TEncoding.Unicode, LBuffer);
-    if Length(LBuffer) = 0 then begin
-      // Now, TEncoding.Convert returns an empty TByte array in files with russion characters
-      // See http://www.heidisql.com/forum.php?t=13044
-      // Re-read the whole chunk + some more bytes
-      // See: Classes.TStreamReader.FillBuffer
-      // See: https://forums.embarcadero.com/message.jspa?messageID=368526
-      MainForm.LogSQL(f_('End of file block was cut within some multibyte character, at position %s. Increasing chunk size and retry reading...', [FormatNumber(Stream.Position)]), lcError);
-      Stream.Position := StartPosition;
-      Inc(ChunkSize, BufferPadding);
-    end else // Success, exit loop
-      Break;
+  while True do begin
     Inc(i);
-    if i=10 then // Give up
+    try
+      SetLength(LBuffer, ChunkSize);
+      Stream.ReadBuffer(Pointer(LBuffer)^, ChunkSize);
+      LBuffer := Encoding.Convert(Encoding, TEncoding.Unicode, LBuffer);
+      // Success, exit loop
       Break;
+    except
+      on E:EEncodingError do begin
+        if i=10 then // Give up
+          Raise;
+        Stream.Position := StartPosition;
+        Inc(ChunkSize, BufferPadding);
+      end;
+    end;
   end;
 
   Result := TEncoding.Unicode.GetString(LBuffer);

source/main.pas

@@ -3816,6 +3816,10 @@ procedure TMainForm.RunQueryFile(FileName: String; Encoding: TEncoding);
         f_('Notice: You can disable the "%s" option to ignore such errors', [actQueryStopOnErrors.Caption])
         );
     end;
+    on E:EEncodingError do begin
+      StopProgress;
+      ErrorDialog(E.Message);
+    end;
   end;
 end;