Generating an IV in C

gistfile1.c

int genIV(
  void* buffer,
  int buffer_len
){
  /* 
   * Note that we propagate the return code from the library called.
   */
#ifndef _WIN32
  return RAND_bytes(buffer, buffer_len); 
#else
  return RtlGenRandom(buffer, buffer_len);
#endif
}