Re: [OT?] Coding Style

[Stephen Satchell]

At 11:56 PM 1/22/01 +0000, Anton Altaparmakov wrote:
>At 16:42 22/01/2001, Mark I Manning IV wrote:
>>Stephen Satchell wrote:
>> >                                              I got in the habit of using
>> >  structures to minimize the number of symbols I exposed. It also
>> > disambiguates local variables and parameters from file- and program-global
>> > variables.
>>
>>explain this one to me, i think it might be usefull...
>
>What might be meant is that instead of declaring variables my_module_var1, 
>my_module_var2, my_module_var3, etc. you declare a struct my_module { 
>var1; var2; var3; etc. }. Obviously in glorious technicolour formatting... (-;
>That's my interpretation anyway...

The first sentence is right on the money.  In addition to module variables, 
I define a global structure as:

      extern struct G {
          /* the real globals */
          } g;

and then in the main program I define the instance as "struct G g;"  This 
is more for apps than operating systems.

Further to the avoidance of pollution of the external global namespace, I 
define local functions as static.  Indeed, in one parser I had over 1400 
very small functions, none of them with external scope.  Instead, I defined 
a structure of function pointers and exposed one name to the rest of the 
world.  Sound stupid?  Well, that stupidity had its place:  the "opcode" in 
the pseudo-instruction stream was the offset into this structure of 
pointers to the pointer of interest, which made the main loop for the 
parser about five lines long, and not a switch statement to be seen.  Three 
of those lines were to handle unknown-opcodes...

I also am partial to arrays of function pointers when appropriate.  Ever 
think how easy it would be to implement a TCP stack that would handle the 
"lamp-test packet" as a single special case?  Granted, it results in a 
small amount of code bloat over the traditional in-line test method, but it 
does make you think about EVERY SINGLE ONE OF THE 64 COMBINATIONS of 
Urg/Ack/Psh/Rst/Syn/Fin (to use the labels from the 1985 version of RFC 
793) and what they really mean.  Especially the combination with all bits set.

Satch