使用LwIP回调编程实现paho开源MQTT库的移植

/ MQTT 数据发送函数
static OSStatus tcp_mqtt_send(struct mqtt_comm_t *mqtt_comm_p, uint8_t data[], uint32_t len, int msBlock, uint8_t apiflag)
{
    mqtt_comm_p->sendbuf = data;
    mqtt_comm_p->sendlen = len;
    mqtt_comm_p->apiflags = apiflag; 
    
    sys_log("tcp_mqtt_send，sendlen: %d.\r\n", mqtt_comm_p->sendlen);

    tcp_send_data(mqtt_comm_p);
    
    if( xSemaphoreTake(mqtt_comm_p->sendsema, msBlock) != pdTRUE )
    {   
        sys_log("tcp send timeout.\r\n");
        return TCP_MQTT_SEND_ERR;
    }
    
   if (mqtt_comm_p->sendlen != 0)  
      return TCP_MQTT_SEND_ERR;
   else
      return NoErr;
}

// TCP 数据发送函数
void tcp_send_data(struct mqtt_comm_t *mqtt_comm_p)
{
    err_t err;
    uint32_t len;

    len = mqtt_comm_p->sendlen;
    len = (len > tcp_sndbuf(mqtt_comm_p->tpcb) ) ?  tcp_sndbuf(mqtt_comm_p->tpcb) : len;
    
    // 连接断开
    if ( (mqtt_comm_p->tpcb == NULL ) || (mqtt_comm_p->tpcb->state != ESTABLISHED) )
    {
        xSemaphoreGive(mqtt_comm_p->sendsema);
        sys_log("tcp_send_data: tpcb error.\r\n");
        return;
    }

    // 发送缓冲区满
    if(tcp_sndbuf(mqtt_comm_p->tpcb) == 0)
    {
        vTaskDelay(1);
        return;
    } 

    do
    {
        err = tcp_write(mqtt_comm_p->tpcb, mqtt_comm_p->sendbuf, len, mqtt_comm_p->apiflags);
        if (err == ERR_MEM)
            len /= 2;
    }
    while (err == ERR_MEM && len > 1);

    if (err == ERR_OK)
    {
        mqtt_comm_p->sendlen -= len;
        mqtt_comm_p->sendbuf += len;
    }
    else
        sys_log("[tcp_send_data]: tcp_write failed.\r\n");    
}

err_t tcp_send_cb(void *arg, struct tcp_pcb *tpcb, u16_t len)
{
  struct mqtt_comm_t *mqtt_comm_p = arg;
  
  if ( mqtt_comm_p->sendlen > 0 )
  {
    tcp_send_data(mqtt_comm_p);
  }
  else
  {
    xSemaphoreGive(mqtt_comm_p->sendsema);
  }
  
  return ERR_OK;
}