OSOP PythonEw

By OSOP

OSOP provides services on development and maintenance of software and hardware for seismological and geophysical solutions. Visit us at http://www.osop.com.pa or send us an email at developers@osop.com.pa. Visit The Seismo Guys blog for occasional insights into scientific programming with Python.

Python wrapper for accessing an Earthworm shared memory ring. Earthworm is a set of opensource programs, tools and libraries that are used in the development of software for maintaining seismic networks, research and other seismological and geophysical applications. http://vps.isti.com/trac/ew/

The main objective of these wrapper-modules is to make it easier for people to contribute to the Earthworm project; developing Earthworm modules using these wrappers is truly a joy as it enables developers to have directy access to memory rings whilst enjoying all the functionality that Python itself brings to the table. Introducing Python into the Earthworm picture will allow new people to come in and contribute.

Although these modules are far from complete, they are currently quite functional and usable; the Tracebuf2 module specially, is already being used in production scenarios, and it has proven to be a very usefull tool.

MODULE OVERVIEW

A module consists of one C and two Python sources. The C source are basically Python-wrapped functions that allow Read/Write operations of a certain Earthworm datatype. One of the Python source contains interfaces to the C wrapped functions; the other Python source is a basic setup tool.

Example:

Tracebuf2
    tracebuf2module/
        tracebuf2module.c
        tracebuf2ring.py
        trace_setup.py

In order to use a module from Python, the C source, in this case tracebuf2module.c, needs to be compiled into a dynamically linked library that Python can load.

HOW TO INSTALL

In order to follow theses steps, Earthworm needs to be previously installed in your computer. Also, note that these are steps for GNU/Linux - UNIX only.

1. Use the makefile included in ring_access/Makefile to create ringwriter.o and ringreader.o. Once created, copy them into the Earthworm's /bin/ directory. Note that you need to edit the INCLUDE and LIBRARIES variables in the makefile to match your Earthworm installation. These are libraries and binaries needed by all the modules.

2. Copy ringwriter.h and ringreader.h into the Earthworm's /include/ directory.

3. Choose the module you want to compile and simply run the corresponding python setup script. Example:

   python trace_setup.py build

This will create a dynamically linked library corresponding to the module, and it's the one that the python module will try to load.