"
This code with SDL-1.2.8 and CVS:

#include <stdio.h>
#include <stdlib.h>
#include <SDL.h>

int
main(int argc, char** argv)
{
   char alphabet[26] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
   char buffer_file[27] = {0};
   char buffer_mem[27]  = {0};
   int rv_file;
   int rv_mem;
   FILE* file_ptr;
   SDL_RWops* rwop_file;
   SDL_RWops* rwop_mem;

   file_ptr = fopen("./blah", "w");
   fwrite(alphabet, 1, sizeof(alphabet), file_ptr);
   fclose(file_ptr);

   rwop_mem  = SDL_RWFromMem(alphabet, sizeof(alphabet));
   rwop_file = SDL_RWFromFile("./blah", "r");
   rv_mem  = SDL_RWread(rwop_mem , buffer_mem,  5, 6);
   rv_file = SDL_RWread(rwop_file, buffer_file, 5, 6);
   printf("From File: %d %s\n"
          "From Mem:  %d %s\n",
	 rv_file,
	 buffer_file,
	 rv_mem,
	 buffer_mem);
   printf("Seek end of File: %d\n"
	 "Seek end of Mem:  %d\n",
	 SDL_RWseek(rwop_file, 0, SEEK_END),
	 SDL_RWseek(rwop_mem , 0, SEEK_END));
   SDL_RWclose(rwop_file);
   SDL_RWclose(rwop_mem);

   return 0;
}


Produces this output:

 From File: 5 ABCDEFGHIJKLMNOPQRSTUVWXYZ
 From Mem:  5 ABCDEFGHIJKLMNOPQRSTUVWXY
Seek end of File: 26
Seek end of Mem:  26
"

--ryan.