/*
 * TermInfo.wcswidth(str)
 *
 * TermInfo.wcswidth returns a the number of columns of str,
 * according to current locale.
 */
static VALUE
rt_wcswidth(VALUE self, VALUE str)
{
  char *s;
  size_t l, r;
  mbstate_t mbs;
  wchar_t wc;
  long cols;
  int width;

#ifdef HAVE_RUBY_ENCODING_H
  /* The encoding of str is assumed to be the locale encoding on Ruby 1.8. */
  str = rb_str_encode(str, rb_enc_from_encoding(rb_locale_encoding()), 0, Qnil);
#endif

  memset(&mbs,0,sizeof(mbstate_t));

  s = StringValueCStr(str);
  l = RSTRING_LEN(str);

  cols = 0;
  while (0 < l) {
    r = mbrtowc(&wc, s, l, &mbs);
    if (r == 0)
      rb_raise(rb_eArgError, "NUL found");

    width = wcwidth(wc);
    if (width == -1)
      rb_raise(rb_eArgError, "non-printable charactor found");
    cols += width;

    l -= r;
    s += r;
  }

  return LONG2NUM(cols);
}