nmapFile.c

void *nmapFile(int sizeInBytes, FILE *myFile) {
     if (myFile) {
          /* Get the file descriptor from the FILE pointer. */
          int fd = fileno(myFile);
          if (fd >= 0) {
                /* Map the file into an unused area of the process's address space. */
                void *result = mmap(
                     NULL,                    /* No preferred address. */
                     sizeInBytes,             /* Size of mapped space. */
                     PROT_READ,               /* Read access. */
                     MAP_FILE,                /* Map from file (default) */
                     fd,                      /* The file descriptor. */
                     0                        /* Offset from start of file. */
                );

                if (result)
                     return result;
          }
     }

     return NULL;
}