zmq源码阅读 —— zmq_send()和zmq_recv()

最新推荐文章于 2025-06-11 06:58:59 发布

bluegreen315

最新推荐文章于 2025-06-11 06:58:59 发布

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分类专栏： zeromq 文章标签： zeromq 源码阅读

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本文详细解析了ZeroMQ（ZMQ）库中消息的接收与发送过程，包括zmq_recv与zmq_send函数的具体实现细节。展示了如何利用ZMQ进行高效的消息传递，并提供了关键步骤的代码示例。

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int zmq_recv (void *s_, void *buf_, size_t len_, int flags_)
{
    if (!s_ || !((zmq::socket_base_t*) s_)->check_tag ()) {
        errno = ENOTSOCK;
        return -1;
    }
    zmq_msg_t msg; // 创建消息结构
    int rc = zmq_msg_init (&msg); // 初始化空消息
    errno_assert (rc == 0);

    zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
    int nbytes = s_recvmsg (s, &msg, flags_); // 接收消息
    if (unlikely (nbytes < 0)) {
        int err = errno;
        rc = zmq_msg_close (&msg);
        errno_assert (rc == 0);
        errno = err;
        return -1;
    }

    //  At the moment an oversized message is silently truncated.
    //  TODO: Build in a notification mechanism to report the overflows.
    size_t to_copy = size_t (nbytes) < len_ ? size_t (nbytes) : len_; //计算消息大小
    memcpy (buf_, zmq_msg_data (&msg), to_copy); // 通过zmq_msg_data()获得消息的data地址，拷贝到buf_中

    rc = zmq_msg_close (&msg); // 释放或销毁消息
    errno_assert (rc == 0);

    return nbytes;
}
---------------------------------------------------------------------
int zmq_recvmsg (void *s_, zmq_msg_t *msg_, int flags_)
{
    return zmq_msg_recv (msg_, s_, flags_);
}
----------------------------------------------------------------------
int zmq_msg_recv (zmq_msg_t *msg_, void *s_, int flags_)
{
    if (!s_ || !((zmq::socket_base_t*) s_)->check_tag ()) {
        errno = ENOTSOCK;
        return -1;
    }
    zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
    int result = s_recvmsg (s, msg_, flags_);
    return result;
}
-----------------------------------------------------------------------
static int
s_recvmsg (zmq::socket_base_t *s_, zmq_msg_t *msg_, int flags_)
{
    int rc = s_->recv ((zmq::msg_t*) msg_, flags_); 
    if (unlikely (rc < 0))
        return -1;
    return (int) zmq_msg_size (msg_);// 计算消息的大小
}
---------------------------------------------------------------------------------
=================================================================================
---------------------------------------------------------------------------------
int zmq_send (void *s_, const void *buf_, size_t len_, int flags_)
{
    if (!s_ || !((zmq::socket_base_t*) s_)->check_tag ()) {
        errno = ENOTSOCK;
        return -1;
    }
    zmq_msg_t msg; // 创建消息结构
    int rc = zmq_msg_init_size (&msg, len_); // 以buf长度初始化成消息
    if (rc != 0)
        return -1;
    memcpy (zmq_msg_data (&msg), buf_, len_); // 将buf的内容拷贝给消息

    zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
    rc = s_sendmsg (s, &msg, flags_); // 发送消息
    if (unlikely (rc < 0)) {
        int err = errno;
        int rc2 = zmq_msg_close (&msg); // 释放和销毁消息
        errno_assert (rc2 == 0);
        errno = err;
        return -1;
    }
    
    //  Note the optimisation here. We don't close the msg object as it is
    //  empty anyway. This may change when implementation of zmq_msg_t changes.
    return rc;
}

从注释中可以看出消息发送的流程，czmq,jzmq等已经做了封装，也可以自己做封装。