Dalke Scientific Software: More science. Less time. Products
[ previous | newer ]     /home/writings/diary/archive/2005/05/18/updated_reseekfile

Updated ReseekFile

I updated ReseekFile. I wrote it two years ago to help probe the contents of file stream coming over a socket connection. I was working with a server that would normally return XML but returned a simple text file if there was an error. It didn't change the headers so I couldn't check the content-type or status code. Instead I checked the first line of the input to check the content directly. If it's XML I needed to reset the data stream so I could pass the file handle to the XML processor.

I'm currently working on a similar project. One quibble I have with ReseekFile is that it keeps everything in memory. Machines have a lot of memory these days but I wanted the option to use the filesystem if need be. For example, if the file is indeed XML then I will be using jing, a Relax-NG validator. That takes a filename so I would prefer just pointing it to that backing file.

I started to write a new class that would have been more complicated than ReseekFile. It would have allowed arbitrary seeks into the file. In the spirit of YAGNI I thought better about it and looked to see if I could modify ReseekFile. I could. It just needed a factory function, to specify how to create a backing store. Turns out I was using the cStringIO's getvalue() to get the size of the buffer file. Real files don't have that so I added a bit of code to track how many bytes I've written to the file.

Download


Andrew Dalke is an independent consultant focusing on software development for computational chemistry and biology. Need contract programming, help, or training? Contact me



Copyright © 2001-2013 Andrew Dalke Scientific AB