From: "David" <nobody AT bogus DOT org>
Newsgroups: comp.os.msdos.djgpp
References: <39A9AA50 DOT FA3AAE59 AT home DOT com>
Subject: Re: __DATA__ in c?
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Date: Mon, 28 Aug 2000 00:39:02 -0400
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

yhvhboy1 wrote in message <39A9AA50 DOT FA3AAE59 AT home DOT com>...
>now, what i am trying to do is save contents of a binary file
>in c, using the djgpp gcc compiler and compile the file
>right in with my c program so i can read from it
>and use its contents...
>kind of like zip2exe, except with the ability
>to write the file where i want and do other things
>besides just unzip a zipfile--
>in other words write more code around it-
>not just do one thing (save a file).
>and i'd like to do it without having to
>store it into an array (would be a problem with say, a .iso
>cd image - or other large files, etc.)


You have to store it to an array.

>and i don't have a clue how to do it.
>comp.lang.c told me to come here and ask
>since it's beyond the core c language.

Here's some sample code that will read in a file, and create a
C-code file declaring a constant array:

======== Cut-here ========
#include <stdio.h>
#include <stdarg.h>

/*****************************************************************
*
* openFile
*
* Convenience wrapper for fopen
******************************************************************
*/
FILE *openFile(const char *fileName, const char *mode)
{
   FILE *f;

   f = fopen(fileName, mode);
   if (f == NULL) {
      printf("Could not open file %s\n", fileName);
      exit(1);
   }
   return(f);
}

/*****************************************************************
*
* main
******************************************************************
*/
int main(void)
{
   FILE *dataFile, *codeFile;
   unsigned char c;
   size_t n;
   int count;

   dataFile = openFile("data.dat", "rb"); // Open for read, in
binary mode
   codeFile = openFile("code.c", "w");    // Open for write, in
text mode

   // Print variable declaration to file
   fprintf(codeFile, "const char data[] = {\n");

   while (!feof(dataFile)) {
      // Print 3 leading spaces for readability
      if (count == 0) {
         printf("   ");
         }

      // Read data from the file 1 character at a time
      fread((void *) &c, sizeof(c), 1, dataFile);
      // Print character to file in hexadecimal
      fprintf(codeFile, "%02X, ", (unsigned int) c);

      // Start new row every eight values
      count = (count + 1) % 8;
      if (count == 0) {
         fprintf(codeFile, "\n");
         }
   }

   // End variable declaration
   fprintf(codeFile, "\n};\n");

   fclose(dataFile);
   fclose(codeFile);

   return(0);
}
======== Cut-here ========

If you save this code as "codefile.c", you can compile it with
this command:

gcc codefile.c -o codefile.exe

For a "data.dat" file with "Hello, world!" in it, I got this
output in "code.c":

========== CODE.C ==========
const char data[] = {
0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x2C, 0x20, 0x77,
0x6F, 0x72, 0x6C, 0x64, 0x21, 0x0D, 0x0A, 0x0D,
0x0A, 0x0A,
};

const long dataSize = 18;
========== CODE.C ==========

Here's some sample code that can access the data:

========== TEST.C ==========
#include <stdio.h>

extern char data[];
extern long dataSize;

int main(void)
{
   long indx;

   for (indx = 0; indx < dataSize; indx++) {
      printf("%c", data[indx]);
   }
}
========== TEST.C ==========

To make the test code, type these commands

gcc -c -Ic:\djgpp\include test.c -o test.o
gcc -c -Ic:\djgpp\include code.c -o code.o
gcc -o test.exe test.o code.o

When you run test.exe, you will get this:

Hello, world!

May God bless you,
David