[Kst] Does kst have any support for data that changes, but doesn't grow?

[Fowler, Joseph W.]

Dear kst team:

I am working on an application where the data set is generated by x-ray sensors called TES microcalorimeters. The raw data are uniformly sampled time series, like in a CMB experiment, but with one key difference: most of our interest is in the random Poisson-distributed "events" that correspond to an x-ray pulse arriving.

I want to convince our team to shift our real-time plotting functions to kst. It will be better in a hundred ways, plus it would remove a serious code maintenance burden if we no longer had to roll our own plots.

One big obstacle is that I can't figure out how to use kst for the data acquisition activity we currently use the most: plotting the most recent fixed-length pulse record from a given calorimeter. (Think: oscilloscope with triggering logic.) We store our data in a non-standard format, so my plan was to start generating an auxiliary, temporary fixed-size dirfile field holding only the latest pulse record. At each trigger, this file gets overwritten. I've tried this concept. The result is that I can plot the dirfile once, but GetData is smart enough not to re-read the dirfile when its contents change. (It does update if--but only if--I click the Reload All Data Sources button.)

My question #1 for you all: Is there any way to convince kst2 (or GetData) that it needs to update a certain data source whose size has not grown? Maybe a clever use of cur-files?

I can see a couple of workarounds, but they have their own problems.  I could just copy all the pulse records to a dirfile and let it grow in the normal way, but this would be a complete duplication of our already large dataset.

Or I could write a kst datasource plugin for our proprietary data files. (The website says to mail this list for help getting started on a plugin. Question #2: Can you help? Is it not so hard? I have plenty of C++ experience.) Our data file format is not dissimilar to a one-field dirfile, but with timestamps interspersed and with a horrible ASCII header tacked on the head.

Or I could just switch our system to writing dirfiles. This might be the best solution, but you can probably imagine there's some institutional inertia resisting this change.

Thanks, gang.
Joe Fowler
NIST Boulder Labs


System details: I am using Mac OS 10.8 with the latest kst2 binary from sourceforge (2.0.7, though I also tried 2.0.6), and the data are being generated in Python through GetData 0.8.5. In our lab environment, we will be running on an Ubuntu Linux system instead.
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