用於從佇列中讀取訊息，其呼叫如下：

string swoole_process->pop(int $maxsize = 8192);

下面我們分析下其流程。

static PHP_METHOD(swoole_process, pop)
{
    long maxsize = SW_MSGMAX;

    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "|l", &maxsize) == FAILURE)
    {
        RETURN_FALSE;
    }

    if (maxsize > SW_MSGMAX || maxsize <= 0)
    {
        maxsize = SW_MSGMAX;
    }

    swWorker *process = swoole_get_object(getThis());
    if (!process->queue)
    {
        swoole_php_fatal_error(E_WARNING, "no msgqueue, can not use pop()");
        RETURN_FALSE;
    }

    struct
    {
        long type;
        char data[SW_MSGMAX];
    } message;

    if (process->ipc_mode == 2)
    {
        message.type = 0;
    }
    else
    {
        message.type = process->id;
    }

    int n = swMsgQueue_pop(process->queue, (swQueue_data *) &message, maxsize);
    if (n < 0)
    {
        RETURN_FALSE;
    }
    SW_RETURN_STRINGL(message.data, n, 1);
}
 

int swMsgQueue_pop(swMsgQueue *q, swQueue_data *data, int length)
{
    int ret = msgrcv(q->msg_id, data, length, data->mtype, q->flags);
    if (ret < 0)
    {
        SwooleG.error = errno;
        if (errno != ENOMSG && errno != EINTR)
        {
            swSysError("msgrcv(%d, %d, %ld) failed.", q->msg_id, length, data->mtype);
        }
    }
    return ret;
}