I’ll be hacking on my hpodder program this weekend. hpodder is a full-featured podcast aggregator that runs on the command line, and has many features over other command-line podcatchers like bashpodder, and even over GUI tools like iPodder.
I originally envisioned hpodder to be something that I’d cron up and run in the background. But I have tended to run it in the foreground more than in the background. Some others have too, and the #1 requested hpodder feature is parallel downloads.
So I am working on that. I already have code working, in fact, that will parallelize both the hpodder update (downloading the feeds) and the hpodder download (downloading the actual episodes) commands.
Unlike ipodder, my code will make sure that no more than 1 thread will ever be downloading from a given server at a given time. ipodder had the terribly annoying habit of pointing all of its threads at a single server, thus pounding it while also providing little benefit for someone with a pipe fatter than the server’s.
Before all this multithreaded stuff could be written, I needed to write my own status bar code instead of just letting curl display its own status bar. (That wouldn’t work when there are 5 curls running at once)
I decided that I would write some generic status bar code, rather than something specific to hpodder. I took the apt-get status bar as an example, and whipped one up in Haskell and added it to my MissingH Haskell library.
But a status bar just begged for another feature: a generalized progress tracker. Something that could keep track of where a task (and its sub-tasks) are, calculate ETA, estimated time remaining, speed, etc. So I wrote that and made the status bar use it.
AND, a status bar begged for a generalized numeric formatter: something that could render 512 as 512, 2048 as 2K, 1048576 as 1M, etc. So I wrote that, and it’s general enough that it can render into both SI and “binary” units by default (and others that users may want).
Finally, I wrote a function to take a number of seconds and render it in something friendly like 23m5s like apt uses, and shoved that in MissingH as well.
So now hpodder will have a status bar, and any other Haskell program can use the same status bar code in minutes because it’s all generic. Or if someone just needs to render a number in megabytes, they can do that.
I really enjoy it when a program needs a solution that is generic enough to put in a larger library. I try to put as much of my Haskell code in MissingH as I can, so as to make it useful to others (and my other programs).