ContextLogger2 Hacking

Sun Jun 5 23:38:41 2011

  1. Logger
  2. Watchdog
  3. Tools

1. Logger

1.1. Design Overview

The solution is based on client software installed on a phone that (typically) runs on the background, unintrusively recording information about activities taking place on the phone. The implementation makes heavy use of event-driven programming, an SQLite database engine, and a Lua runtime. More specifically: each “sensor” runs independently as its own “active object”, reacting to system events; all persistent data (including any logged data) is managed with SQLite; and configurability of the system revolves around the lightweight dynamic language Lua.

1.2. General Design Guidelines

The implementation of the logger daemon has been influenced by these guidelines:

1.3. Adding a New Sensor

The steps to take when adding a new sensor are typically like this:

  1. Specify a database table for recording the sensor readings in src/ If you want a compile-time option for the sensor, specify it here; something like ``__SENSORNAME_ENABLED__``.
  2. If you have a compile-time option for the sensor, enable it for desired variant builds by editing the variants/* files. If you want to compute a default setting based on other compile-time configuration options, you can do this in variants/
  3. Take a similar sensor implementation as a template for the interface and implementation files. (An example of such files would be src/epoc-cellid.hpp and src/epoc-cellid.cpp.) Copy, rename, and modify to implement your required sensor.
  4. Add an #include for the header file of your sensor in src/sa_array.cpp. Also add a DECLARE_SENSOR_sensorname style declaration, or otherwise declare your sensor active object in the _sa_Array object.
  5. List your implementation file in Makefile and/or the src/ file as appropriate. (The former is required for Linux builds, whereas the latter is required for Symbian builds.) Again, if you had a compile-time option for your sensor, you may want to make use of it here.
  6. If your sensor implementation relies on system DLLs, you should ensure they are listed in Makefile and/or src/ as appropriate. Again, if you had a compile-time option for your sensor, you may want to make use of it here; this is particularly important if the libraries used are not included in all SDKs.

As an example of the code required for a single sensor, below is a patch showing a sensor implemented based on the Adaptive History List API:

2. Watchdog

3. Tools

3.1. Koog

Koog is a mixed-code generation tool that we have used in maintaining the logger codebase, mostly interactively under Emacs. In case you're wondering about the /***koog***//***end***/ style comments found in the code. If these comments get on the way, feel free to delete them. It is quite possible to maintain the boilerplate code manually as well.

Tero Hasu