Question

Or is it better to go with common C functions?

Answer 1

There is an I/O API in SDL, I’m not sure if it’s any easier though, but it should be portable. Those are the relevant functions:

SDL_RWops *SDL_RWFromFile(const char *file, const char *mode); // open file
SDL_RWread(ctx, ptr, size, n); //read from file
SDL_RWclose(ctx)   //close file

There’s an example here that shows how to open and read from a file.

#include <stdio.h>
#include "SDL_rwops.h"
int main()
{
  int blocks;
  char buf[256];
  SDL_RWops *rw=SDL_RWFromFile("file.bin","rb");
  if(rw==NULL) {
    fprintf(stderr,"Couldn't open file.bin\n");
    return(1);
  }

  blocks=SDL_RWread(rw,buf,16,256/16);
  SDL_RWclose(rw);
  if(blocks<0) {
    fprintf(stderr,"Couldn't read from file.bin\n");
    return(2);
  }

  fprintf(stderr,"Read %d 16-byte blocks\n",blocks);
  return(0);
}

Edit:There’s a tutorial here on the file API, it may be easier to use when loading images:

http://www.aspfree.com/c/a/c-sharp/game-programming-using-sdl-the-file-io-api/