inferno programmer's notebook

I've been occupied recently with archiving my digital media. I've been copying home videos on DV tapes to hard-disk, ripping audio CD's to WAV files, gathering photo collections, and trying to copy documents from Iomega disks, floppies, and my dusty old Acorn RiscPC. The plan is to have a copy of this data to give to each of my children. My Dad recently scanned and sent me all his photographs of me and my siblings growing up; he also included pictures of himself and my Mother when they met in Africa. With technology today each generation can build a digital library of family history to hand on to the next generation. In the past a family album may have been passed on to only one person. The accumulation of digital data still presents problems. It requires discipline to store files that are open and not locked into devices or proprietary formats. With digital preservation in mind I've tried to use file formats recommended for long term archiving. WAV files for audio, D

There has been a three and a half year gap in my posts to this blog. In that time I hadn't done any Limbo programming. I've used Acme as my editor everyday, but I was drifting towards using Notepad++ more often. In the past couple of months I've had the time to contemplate doing some hacking projects. I wanted to explore what I could do with Inferno for multimedia file types. This lab was the first thing I tackled in using Inferno again. I had to open up the Limbo paper to remember even some basic syntax. It bothered me that wm/view only displayed images using the Inferno 256 color map. Charon didn't have this limitation and I thought it had something to do with their respective image libraries. They don't use the same code. I extracted Charon's img.b code out into another view tool only to realize once I'd finished that the difference was not in the handling of JPEGs or PNGs but in the remap of the raw image to an Inferno image after the image was load

wavplay plays a WAV file. It is merely a combination of the wav2iaf and the auplay commands already in Inferno. I have no audio in IAF format, but I am putting together 100s of GBs of wav files as I'm ripping my CD collection. % bind '#A' /dev % wavplay track.wav FILES wavplay.b

NAME lab 107 - midiplay NOTES Midiplay plays back MIDI files. It uses the synthesizer I described in lab 62 and the MIDI module from lab 73. The command takes only one argument, the path to the midi file. I've included one in the lab to demonstrate. Bind the audio device before using it. % bind -a '#A' /dev % midiplay invent15.mid The synthesizer has 16 note polyphony. It uses three oscillators, one at the pitch, one at half pitch, one at double pitch. There is also a filter, two delays and a vibrato. The sample rate is 8000hz and there is one mono channel (MIDI channel events are ignored). It performs well enough to work on my laptop without JIT turned on. All the synthesizer parameters can only be tweaked from inside the code at the moment. FILES lab - 107

NAME lab 106 - UNIX RUDP Support NOTES A simple port of the Inferno native RUDP support to a standalone UNIX environment (with a client and server example). This particular example is single threaded and specifically intended for use with synchronous RPC mechanisms (in this particular instance a synchronous 9P client and server). It could probably be greatly improved in several dimensions, but this example should provide a minimal implementation which more complicated incarnations can be built off of. Enjoy. FILES 106/Makefile 106/client.c 106/rudp.c 106/rudp.h 106/server.c

NAME lab 105 - automount NOTES A small modification to mntgen yields an automounter which automatically mounts a server based on path name. This is a fairly crude proof of concept with hardwired port numbers and top-level mount path -- but it would be fairly easy to make it a bit more robust. Essentially, I just added a mount command to the code which dynamically adds the directory node to the mntgen tree on reference. Then I made the file system handling call its own thread so that the mount could reference the synthetic without locking up the original single threaded synthetic file server. One problem is that unknown servers take some time to respond with file note found, which is less than desirable. Fixing this and other annoyances is left as an exercise for the reader. EXAMPLE % ls /amnt % mount {automnt} /amnt % ls /amnt % ls /amnt/localhost/usr/inferno /amnt/localhost/usr/inferno/9cpu /amnt/localhost/usr/inferno/README /amnt/localhost/usr/inferno/charon /amnt/localhos

NAME lab 104 - ducts: bi-directional mount channels NOTES Hi there, I want to talk to you about ducts. Are your ducts old fashion, out of date? In this lab, I'll walk through a little facility I built to allow me to have bi-directional mounts over a single file descriptor channel. The nature of the way I access my Blue Gene environment requires me to do an awful lot over a single communications channel. I wanted the ability to both access the target node's file system while simultaneously exporting mine, while only using a single file descriptor. To facilitate this, I wrote a little 9P-knowledgeable multiplexor which directs T-msgs to an export thread and R-msgs to a mount thread while multiplexing the responses from those threads back onto the same file descriptor. The initial implementation of the base mechanism was relatively simple until I had to start considering how to clean things up when I started unmounting directories on one side or both. The liberal use of sys-

NAME lab 103 - python content assist NOTES Building on lab 102 I've started to write an acme client for python content-assist in python. I read the code for python's IDLE editor and pulled some pieces out of that to help with my implementation. The AutoComplete.py and CallTip.py modules are copied out of idlelib and reduced to just the functions I needed. Just as in lab 102 the acme client is implemented using pyxp to connect to the acme file system. In an acme editor window execute PyAssist. Start typing some python. After typing a dot the client will display available attributes for the module. Continue typing and it will reduce the list to those names with a matching prefix. Press the Tab key to complete a name or prefix depending on whether there is one or more names. After typing an open parenthesis the client will show the call tip for the function. The client implements an Import command so that more python modules can be added to the namespace. PyAssist