chr

static VALUE
int_chr(int argc, VALUE *argv, VALUE num)
{
    char c;
    unsigned int i = NUM2UINT(num);
    rb_encoding *enc;

    switch (argc) {
      case 0:
        if (i < 0) {
          out_of_range:
            rb_raise(rb_eRangeError, "%d out of char range", i);
        }
        if (0xff < i) {
            enc = rb_default_internal_encoding();
            if (!enc) goto out_of_range;
            goto decode;
        }
        c = (char)i;
        if (i < 0x80) {
            return rb_usascii_str_new(&c, 1);
        }
        else {
            return rb_str_new(&c, 1);
        }
      case 1:
        break;
      default:
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 0..1)", argc);
        break;
    }
    enc = rb_to_encoding(argv[0]);
    if (!enc) enc = rb_ascii8bit_encoding();
  decode:
    return rb_enc_uint_chr(i, enc);
}