Parser reads from input file small chunks (8192 churacters) and feed FeedParser which pushes data into BufferedSubFile. In BufferedSubFile.push() chunks of incomplete data are accumulated in a buffer and repeatedly scanned for newlines. Every push() has linear complexity from the size of accumulated buffer, and total complexity is quadratic.

Here is a patch which fixes problem with parsing long lines. Feel free to add comments if they are needed (there is an abundance of comments in the module).