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
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