Waitset Use Cases

Using WaitSets and Conditions. More...

Using WaitSets and Conditions.

The following #includes are needed for the examples on this page

#include <iostream>
#include <dds/core/ddscore.hpp>
#include <dds/sub/ddssub.hpp>

Setting up a WaitSet

• Create a WaitSet and attach Conditions

      // Create a WaitSet
      dds::core::cond::WaitSet waitset;
  
      // Create a GuardCondition
      dds::core::cond::GuardCondition guard_cond;
  
      // Create a StatusCondition for a given Entity
      dds::core::cond::StatusCondition status_cond(entity);
  
      // Create a ReadCondition for a reader with a specific DataState
      dds::sub::cond::ReadCondition read_cond(
          reader, dds::sub::status::DataState(
              dds::sub::status::SampleState::not_read(),
              dds::sub::status::ViewState::any(),
              dds::sub::status::InstanceState::any()));
  
      // Attach conditions
      waitset += guard_cond; // using += operator
      waitset += status_cond;
      waitset.attach_condition(read_cond); // or using attach_condition()

Waiting for Condition(s) to trigger

You have two ways to wait for Conditions to trigger: wait or dispatch.

• Wait example

      // Wait for at most 20 seconds until one or more conditions are active and
      // then return them.
      // In case of timeout, active_conditions will be empty.
      dds::core::cond::WaitSet::ConditionSeq active_conditions =
          waitset.wait(dds::core::Duration::from_secs(20));
  
      for (uint32_t i = 0; i < active_conditions.size(); i++) {
          if (active_conditions[i] == guard_cond) {
              std::cout << "guard_cond was triggered\n";
          } else if (active_conditions[i] == status_cond) {
              std::cout << "status_cond was triggered\n";
          } // ...
      }

  
  
• Dispatch example

      // create a WaitSet
      dds::core::cond::WaitSet waitset;
  
      // Create a ReadCondition for reader1 with a functor handler, like this
      // C++11 lambda
      dds::sub::cond::ReadCondition read_cond1(
          reader1,
          dds::sub::status::DataState::any(),
          []()
          {
              std::cout << "read_cond1 was triggered\n";
          }
      );
  
      dds::sub::cond::ReadCondition read_cond2(
          reader2,
          dds::sub::status::DataState::any(),
          []()
          {
              std::cout << "read_cond2 was triggered\n";
          }
      );
  
      // Attach conditions
      waitset += read_cond1;
      waitset += read_cond2;
  
      // Wait at most 20 seconds until one or more conditions are active and
      // then call the handler of the active conditions
      waitset.dispatch(dds::core::Duration::from_secs(20));