zmq_init 源码学习

void *zmq_init (int io_threads_)
{ 
    if (io_threads_ >= 0) {
        void *ctx = zmq_ctx_new ();  
        zmq_ctx_set (ctx, ZMQ_IO_THREADS, io_threads_);
        return ctx;      
    }
    errno = EINVAL;      
    return NULL;
}

//  New context API

void *zmq_ctx_new (void)
{
    //  We do this before the ctx constructor since its embedded mailbox_t
    //  object needs the network to be up and running (at least on Windows).
    if (!zmq::initialize_network ()) {
        return NULL;
    }

    //  Create 0MQ context.
    zmq::ctx_t *ctx = new (std::nothrow) zmq::ctx_t; /* 这里使用的是不抛出异常的new，因为zmq作为库来说，要与不支持异常的调用者兼容，如C。*/
    if (ctx) {
        if (!ctx->valid ()) {
            delete ctx;
            return NULL;
        }
    }
    return ctx;
}

zmq::ctx_t::ctx_t () :
    _tag (ZMQ_CTX_TAG_VALUE_GOOD),
    _starting (true),
    _terminating (false),
    _reaper (NULL),
    _max_sockets (clipped_maxsocket (ZMQ_MAX_SOCKETS_DFLT)),
    _max_msgsz (INT_MAX),
    _io_thread_count (ZMQ_IO_THREADS_DFLT),
    _blocky (true), 
    _ipv6 (false),
    _zero_copy (true)
{    
#ifdef HAVE_FORK
    _pid = getpid ();
#endif
#ifdef ZMQ_HAVE_VMCI
    _vmci_fd = -1;
    _vmci_family = -1;
#endif

    //  Initialise crypto library, if needed.
    zmq::random_open ();
}

zmq::reaper_t::reaper_t (class ctx_t *ctx_, uint32_t tid_) :
    object_t (ctx_, tid_),
    _mailbox_handle (static_cast<poller_t::handle_t> (NULL)),
    _poller (NULL),
    _sockets (0),
    _terminating (false)
{
    if (!_mailbox.valid ())
        return;
     /* Linux下，poller_t实际上即为epoll_t*/
    _poller = new (std::nothrow) poller_t (*ctx_);
    alloc_assert (_poller);
    //这里的mailbox.get_fd()得到该reaper_t拥有的mailbox的读描述符
    if (_mailbox.get_fd () != retired_fd) {
        _mailbox_handle = _poller->add_fd (_mailbox.get_fd (), this);
        _poller->set_pollin (_mailbox_handle);
    }

#ifdef HAVE_FORK
    _pid = getpid ();
#endif
}