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// Copyright (c) 2022 by Apex.AI Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
#pragma once
#include "iceoryx_posh/popo/wait_set.hpp"
#include "iceoryx_posh/runtime/service_discovery.hpp"
#include <atomic>
#include <vector>
namespace discovery
{
using ServiceDiscovery = iox::runtime::ServiceDiscovery;
using ServiceContainer = std::vector<iox::capro::ServiceDescription>;
ServiceDiscovery& serviceDiscovery();
/// @brief User defined discovery with wait functionality that allows
/// to wait until some (discovery related) condition is true.
class Discovery
{
public:
Discovery();
/// @brief wait until service availability changes AND some condition evaluates to true
/// @param condition condition with signature bool(void)
/// @return true if the condition held, false otherwise (i.e. was unblocked)
/// @note blocks the current thread, can be unblocked by unblockWait (as a final action)
template <typename Condition>
bool waitUntil(const Condition& condition);
/// @brief wait for any change of the registry since the last update
void waitUntilChange();
/// @brief unblock any wait
/// @note not reversible, i.e. after this call no further waiting with e.g. waitUntil is possible
void unblockWait();
/// @brief get all services matching a findService query
/// @note invokes findService of the native iceoryx ServiceDiscovery API
ServiceContainer findService(const iox::cxx::optional<iox::capro::IdString_t>& service,
const iox::cxx::optional<iox::capro::IdString_t>& instance,
const iox::cxx::optional<iox::capro::IdString_t>& event);
private:
ServiceDiscovery* m_discovery{nullptr};
iox::popo::WaitSet<1> m_waitset;
std::atomic_bool m_blocking{true};
};
//! [wait until condition]
template <typename Condition>
bool Discovery::waitUntil(const Condition& condition)
{
do
{
// 1) does the condition hold?
bool result = condition();
if (result)
{
// 2) condition held and we return (without mutex to protect condition changes
// there is no way to guarantee it still holds)
return true;
}
else
{
if (!m_blocking)
{
return false;
}
}
// 3) condition did not hold but it may hold if we use the latest discovery data
// which may have arrived in the meantime
// 4) this does not wait if there is new discovery data (and hence we try again immediately)
waitUntilChange();
// 5) discovery data changed, check condition again (even if unblocked)
} while (true);
return false;
}
//! [wait until condition]
} // namespace discovery
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