Hello everybody,
I'm looking for a nice solution.
One of my programs has a lot of strings in it; about 20% of binary size, or
something like that. Now most of them are rarely used - error messages
like "Cannot write to file", "No space left while allocating memory", etc.
I tried to compress just the help texts in the binary - and saved 11k
without any other modification.
Now I'd like to wrap that in some magic macro, so that it looks like that:
char *text=C("text");
Then there could be
#if USE_COMPRESSED_TEXT
#define C(x) ...
#else
#define C(x) x
#endif
but that's where I'm stuck.
It's easy to write a function that takes a pointer to some compressed space
and returns a pointer to the uncompressed data (re-entry is no problem).
I don't know how to get the transformation while compiling.
- I could try #define C(x) uncompress(buffer##__LINE__) and write some
script that looks for the C() calls and generates a C file with the
buffer constants - which means parsing (some of) C.
- Or these texts get put in some special segment, that gets compressed into
another before linking, and the original segment gets removed.
- Or, what I'd like best: Is there some way to tell GCC "whenever this
macro is used, call program X, and substitute the macro value with the
output"? That would be the easiest way for me.
Now you might say that it isn't that interesting - just use a compressed
filesystem, or whatever. But these are all different tradeoffs; I'd just
like to reduce the storage (and typical memory) footprint of my application
by storing rarely used data compressed. I'd imagine that other projects
would use that too, if it's easily available - and then the space needed
for a small installation would decrease by some non-trivial amount.
And, not at least, allowing dynamic macro expansion would allow some neat
hacks :-)
Please keep me CC:ed; thank you for all ideas, tips and other feedback.
Regards,
Phil
--
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Try fsvs (fsvs.tigris.org)!
