str_dup(UChar* s, UChar* end)
{
  int len = end - s;

  if (len > 0) {
    UChar* r = (UChar* )xmalloc(len + 1);
    CHECK_NULL_RETURN(r);
    xmemcpy(r, s, len);
    r[len] = (UChar )0;
    return r;
  }
  else return NULL;
}
str_dup(UChar* s, UChar* end)
{
  int len = end - s;

  if (len > 0) {
    UChar* r = (UChar* )xmalloc(len + 1);
    CHECK_NULL_RETURN(r);
    xmemcpy(r, s, len);
    r[len] = (UChar )0;
    return r;
  }
  else return NULL;
}