Waitset Use Cases

Using wait-sets and conditions. More...

Using wait-sets and conditions.

Setting up a wait-set

• Create a wait-set

  DDSWaitSet* waitset = new DDSWaitSet();

• Attach conditions

  DDSCondition* cond1 = ...;
  DDSCondition* cond2 = entity->get_statuscondition();
  DDSCondition* cond3 = reader->create_readcondition(DDS_NOT_READ_SAMPLE_STATE,
                                               DDS_ANY_VIEW_STATE,
                                               DDS_ANY_INSTANCE_STATE);
  DDSCondition* cond4 = new DDSGuardCondition();
  DDSCondition* cond5 = ...;
  DDS_ReturnCode_t retcode;
  
  retcode = waitset->attach_condition(cond1);
  if (retcode != DDS_RETCODE_OK) {
      // ... error
  }
  retcode = waitset->attach_condition(cond2);
  if (retcode != DDS_RETCODE_OK) {
      // ... error
  }
  retcode = waitset->attach_condition(cond3);
  if (retcode != DDS_RETCODE_OK) {
      // ... error
  }
  retcode = waitset->attach_condition(cond4);
  if (retcode != DDS_RETCODE_OK) {
      // ... error
  }
  retcode = waitset->attach_condition(cond5);
  if (retcode != DDS_RETCODE_OK) {
      // ... error
  }

Waiting for condition(s) to trigger

• Set up a wait-set

• Wait for a condition to trigger or timeout, whichever occurs first

  DDS_Duration_t timeout = { 0, 1000000 }; // 1ms
  
  DDSConditionSeq active_conditions; // holder for active conditions
  
  bool is_cond1_triggered = false;
  bool is_cond2_triggered = false;
  
  DDS_ReturnCode_t retcode;
  
  retcode = waitset->wait(active_conditions, timeout);
  
  if (retcode != DDS_RETCODE_OK) {
      if (retcode == DDS_RETCODE_TIMEOUT) {
          // Timeout
      } else {
          // Failure
  } else {
      // success, check if "cond1" or "cond2" are triggered:
          for(int i = 0; i < active_conditions.length(); ++i) {
  
             if (active_conditions[i] == cond1) {
                printf("Cond1 was triggered!");
                is_cond1_triggered = true;              
             }
  
             if (active_conditions[i] == cond2) {
                printf("Cond2 was triggered!");
                is_cond2_triggered = true;              
             }
  
             if (is_cond1_triggered && is_cond2_triggered) {
                break;
             }   
         }   
  }  
  
  if (is_cond1_triggered) {
      // ... do something because "cond1" was triggered ...
  }
  
  if (is_cond2_triggered) {
      // ... do something because "cond2" was triggered ...
  }
  
  return retcode;

Tearing down a wait-set

• Delete the wait-set

  delete waitset;
  waitset = NULL;