to_json

static VALUE mHash_to_json(int argc, VALUE *argv, VALUE self)
{
    VALUE Vstate, Vdepth, result;
    long depth;

    rb_scan_args(argc, argv, "02", &Vstate, &Vdepth);
    depth = NIL_P(Vdepth) ? 0 : FIX2LONG(Vdepth);
    if (NIL_P(Vstate)) {
        long len = RHASH_SIZE(self);
        result = rb_str_buf_new(len);
        rb_str_buf_cat2(result, "{");
        rb_hash_foreach(self, hash_to_json_i, result);
        rb_str_buf_cat2(result, "}");
    } else {
        GET_STATE(Vstate);
        check_max_nesting(state, depth);
        if (state->check_circular) {
            VALUE self_id = rb_obj_id(self);
            if (RTEST(rb_hash_aref(state->seen, self_id))) {
                rb_raise(eCircularDatastructure,
                        "circular data structures not supported!");
            }
            rb_hash_aset(state->seen, self_id, Qtrue);
            result = mHash_json_transfrom(self, Vstate, LONG2FIX(depth));
            rb_hash_delete(state->seen, self_id);
        } else {
            result = mHash_json_transfrom(self, Vstate, LONG2FIX(depth));
        }
    }
    OBJ_INFECT(result, self);
    FORCE_UTF8(result);
    return result;
}