Re: [Playerstage-developers] Request() call and dynamic request data size

[Paul O. <new...@ki...>]

On Thu, 15 Nov 2007, Toby Collett wrote:

> With the dynamic array sizes you cannot do simple tests to check the size of
> the incoming packets..basically you just have to trust that player is
> passing you a valid data packet. If you want to be double certain then you
> can test that it is at least the size of the base structure...
>
> The len field in publish is actually ignored rather than being optional, The
> one in Request is also ignored, although it gets passed on for a long time
> first.
>
> Toby
Hi Toby,

Looks like it works, it's enough to replace this condition with following 
one:
if ((msg->GetDataSize()) < (sizeof(player_simulation_pose2d_req_t)))
{
   PLAYER_WARN2(....);
} else
{
   //ok
}

Thanks,
Paul

>
> On 15/11/2007, Paul Osmialowski <new...@ki...> wrote:
>>
>> Hi Toby,
>>
>> I'm trying to rewrite some plugin driver so it could be compiled with CVS
>> version of libplayercore. As we know, currently Publish() method parameter
>> that denotes the size of published data packet is optional and has default
>> value 0, which means, the size of the data can be dynamic and is computed.
>> In my driver I'm also using Request() method to send
>> PLAYER_SIMULATION_REQ_GET_POSE2D request, which means I have to fill
>> fields in player_simulation_pose2d_req_t structure. One of them (called
>> 'name') has dynamic size. Unfortunately, 'len' parameter of Request()
>> method isn't optional, so I guess I have to pass size of the
>> player_simulation_pose2d_req_t structure.
>> My code is:
>>
>> #define STRNCPY(dest, src, n) do \
>> { \
>>    strncpy(dest, src, n); \
>>    ((dest)[n-1]) = 0; \
>> } while (0)
>>
>>      player_position2d_data_t posdata;
>>      Message * msg;
>>      player_simulation_pose2d_req_t posreq, * posreq_new;
>>      memset(&posdata, 0, sizeof posdata);
>>      memset(&posreq, 0, sizeof posreq);
>>      posreq.name_count = strlen(this->object) + 1;
>>      posreq.name = new char[posreq.name_count];
>>      assert(posreq.name);
>>      STRNCPY(posreq.name, this->object, posreq.name_count);
>>      msg = this->simulation_dev->Request(this->InQueue,
>>                                          PLAYER_MSGTYPE_REQ,
>>                                          PLAYER_SIMULATION_REQ_GET_POSE2D,
>>                                          (void *)(&posreq),
>>                                          sizeof posreq,
>>                                          NULL, true);
>>      delete []posreq.name;
>>      posreq.name = NULL;
>>      if (!msg)
>>      {
>>        PLAYER_WARN("failed to acquire position data");
>>      } else
>>      {
>>        if ((msg->GetDataSize()) !=
>> (sizeof(player_simulation_pose2d_req_t)))
>>        {
>>          PLAYER_WARN2("invalid acqired data size %d vs %d",
>> msg->GetDataSize(), sizeof(player_simulation_pose2d_
>> req_t));
>>        } else
>>        {
>>          posreq_new = (player_simulation_pose2d_req_t
>> *)(msg->GetPayload());
>>          if (!posreq_new)
>>          {
>>            PLAYER_WARN("no data acquired");
>>          } else
>>          {
>>            posdata.pos.px = posreq_new->pose.px;
>>            posdata.pos.py = posreq_new->pose.py;
>>            posdata.pos.pa = posreq_new->pose.pa;
>>          }
>>        }
>>        delete msg;
>>      }
>>      msg = NULL;
>>
>> As a result I'm getting warning:
>> invalid acqired data size 35 vs 32
>>
>> What went wrong?
>> This code worked before recent changes...
>>
>> Cheers,
>> Paul
>>
>>
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>
>
>
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