Is there an iPad/iPhone app that can handle editing large (~10000 line) text files? I'm looking for an iPad/iPhone app that can handle editing large (~10000 line) text files. I would like this app to be able to access a particular Dropbox file quickly, and after editing have the file be updated on Dropbox.

Finally, I would be happy if it only allows me to edit the first few lines, or to add to the top of a particular file. (I currently have a cronjob which does this -- I edit a particular blank text file, and the cronjob adds it to the top of the larger file, but would like a more direct solution.)
If adding to the front of a file is OK then I use Drafts for this.

It allows you to type some text and have it added to the front ("prepended") of a file in Dropbox. It can even automatically add the date.

I'm not sure if it has a limit to the length of the file, mine are only a hundred or so lines.

Drafts allows you to type some test and quickly perform any number of actions with it. One of my highly recommended iOS applications.