How to store data inside the executable file

Question

I need to find a way to store 250 KB of plain text numbers inside my program's executable file.

Usually, I would put the data in a separate file and let the program read it while it is running, but that's not an option here. Instead, the program and the data need to be in one executable file.

I have absolutely no idea how to do it (except writing 250.000 #defines :-) and I'd appreciate any suggestions.

Answer 1

How about an array of some sort. Just put that definition in a file and compile it into your program:

int external_data[] =
{
    ...
};

you can have the compiler tell you how many elements are in external data:

size_t external_data_max_idx = sizeof(external_data) / sizeof(*external_data);

Answer 2

You could just generate an array definition. For example, suppose you have numbers.txt:

$ head -5 numbers.txt
0.99043748698114
0.0243802034269436
0.887296518349228
0.0644020236531517
0.474582201929554

I've generated it for the example using:

$ perl -E'say rand() for (1..250_000)' >numbers.txt

Then to convert it to C array definition you could use a script:

$ perl -lpE'BEGIN{ say "double data[] = {"; }; 
>     END{ say "};" }; 
>     s/$/,/' > data.h < numbers.txt 

It produces:

$ head -5 data.h
double data[] = {
0.99043748698114,
0.0243802034269436,
0.887296518349228,
0.0644020236531517,

$ tail -5 data.h
0.697015237317363,
0.642250552146166,
0.00577098769553785,
0.249176256744811,
};

It could be used in your program as follows:

#include <stdio.h>    
#include "data.h"

int main(void) {
  // print first and last numbers
  printf("%g %g\n", data[0], data[sizeof(data)/sizeof(*data)-1]);
  return 0;
}

Run it:

$ gcc *.c && ./a.out
0.990437 0.249176