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by Andrew Dalke.
Original Post: Updated ReseekFile
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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.
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