Thread::SizedQueue.new

static VALUE
rb_szqueue_initialize(VALUE self, VALUE vmax)
{
    long max;
    struct rb_szqueue *sq = szqueue_ptr(self);

    max = NUM2LONG(vmax);
    if (max <= 0) {
        rb_raise(rb_eArgError, "queue size must be positive");
    }

    RB_OBJ_WRITE(self, szqueue_list(sq), ary_buf_new());
    ccan_list_head_init(szqueue_waitq(sq));
    ccan_list_head_init(szqueue_pushq(sq));
    sq->max = max;

    return self;
}