Monday, 14 October 2013

Determining what to Change

God grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.

This wisdom is generally what we may lack at the crucial time when the code is handled for changing. We change things that might have had other impacts, dependencies and as a result of which our entire effort might just have to be redone.

Following in from the previous brief discussion of the various function calls made, we can clearly distinguish between the two groups.

The major goal of the entire project being the transition from the use of select to efficiently make use of the epoll mechanism, the majority of the work involved in playing with socket based calls. It is clear that no initialization functions need any sort of tweaks.

The file or the function that has to be majorly changed is of course select_loop( ) itself!
The file select.c contains the major logic of the select statement which needs to be adapted for epoll.
Also, the processing is done in the form of queues. Three different types of queues are used for processing the requests. These do not require any major changes but for the dependence on their use of the structure request.

Examining dependencies further, we come across a structure - struct request which stores the incoming request details and is further used for processing the actual request. Defined in the globals.h file, it is now marked for change to incorporate the epoll based event structure.

A deluge of pointers awaits as we explore the files request.c and response.c. Mainly used for processing the request structure, they become potential candidates and so does buffer.c which contains functions which help in buffering the data before sending it to the client. To he file, get.c performs a part to get the headers of the incoming request. Reading and writing involves the use of pipes and hence the file, pipe.c is another contender. Inspecting further, it is found that the file cgi.c may need minor tweaks for it uses the file descriptor from the request structure.

Here, we have now enumerated the ones that possibly need to be changed. Now let us look at them in detail so as to understand them better.

1 comment:

  1. It would be helpful if you can also work out the FSM and post the FSM diagram of boa request processing and response generation. This will provide required clarity in much better details to you as well as to other readers/developers.