DomainImpl.h

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// SPDX-FileCopyrightText: Deutsches Elektronen-Synchrotron DESY, MSK, ChimeraTK Project <chimeratk-support@desy.de>
// SPDX-License-Identifier: LGPL-3.0-or-later
#pragma once
 
#include "../VersionNumber.h"
#include "AsyncNDRegisterAccessor.h"
#include "Domain.h"
#include "SubDomain.h"
 
#include <functional>
 
namespace ChimeraTK::async {
 
  template<typename BackendDataType>
  class DomainImpl : public Domain {
   public:
    DomainImpl(boost::shared_ptr<DeviceBackend> backend, size_t domainId) : _backend(backend), _id(domainId) {}
 
    VersionNumber distribute(BackendDataType data, VersionNumber version = VersionNumber{nullptr});
 
    VersionNumber activate(BackendDataType data, VersionNumber version = VersionNumber{nullptr});
 
    void deactivate() override;
    void sendException(const std::exception_ptr& e) noexcept override;
 
    template<typename UserDataType>
    boost::shared_ptr<AsyncNDRegisterAccessor<UserDataType>> subscribe(
        RegisterPath name, size_t numberOfWords, size_t wordOffsetInRegister, AccessModeFlags flags);
 
   protected:
    // Everything in this class is protected by the mutex from the Domain base class.
    boost::weak_ptr<SubDomain<BackendDataType>> _subDomain;
 
    boost::shared_ptr<DeviceBackend> _backend;
    size_t _id;
 
    // Data to resolve a race condition (see distribute and activate)
    BackendDataType _notDistributedData;
    VersionNumber _notDistributedVersion{nullptr};
    VersionNumber _activationVersion{nullptr};
  };
 
  /********************************************************************************************************************/
 
  template<typename BackendDataType>
  VersionNumber DomainImpl<BackendDataType>::distribute(BackendDataType data, VersionNumber version) {
    std::lock_guard l(_mutex);
    // everything incl. potential creation of a new version number must happen under the lock
    if(version == VersionNumber(nullptr)) {
      version = {};
    }
 
    if(!_isActive) {
      // Store the data. We might need it later if the data in activate is older due to a race condition.
      _notDistributedData = data;
      _notDistributedVersion = version;
      return VersionNumber{nullptr};
    }
 
    if(version < _activationVersion) {
      return VersionNumber{nullptr};
    }
 
    auto subDomain = _subDomain.lock();
    if(!subDomain) {
      return VersionNumber{nullptr};
    }
 
    subDomain->distribute(data, version);
    return version;
  }
 
  /********************************************************************************************************************/
 
  template<typename BackendDataType>
  VersionNumber DomainImpl<BackendDataType>::activate(BackendDataType data, VersionNumber version) {
    std::lock_guard l(_mutex);
    // everything incl. potential creation of a new version number must happen under the lock
    if(_isActive) {
      return VersionNumber(nullptr);
    }
 
    if(version == VersionNumber(nullptr)) {
      version = {};
    }
 
    _isActive = true;
 
    auto subDomain = _subDomain.lock();
    if(!subDomain) {
      return VersionNumber{nullptr};
    }
 
    if(version >= _notDistributedVersion) {
      subDomain->activate(data, version);
      _activationVersion = version;
    }
    else {
      // Due to a race condition, it has been tried to distribute newer data before activate was called.
      subDomain->activate(_notDistributedData, _notDistributedVersion);
      _activationVersion = _notDistributedVersion;
    }
    return _activationVersion;
  }
 
  /********************************************************************************************************************/
 
  template<typename BackendDataType>
  void DomainImpl<BackendDataType>::deactivate() {
    std::lock_guard l(_mutex);
 
    _isActive = false;
  }
 
  /********************************************************************************************************************/
 
  template<typename BackendDataType>
  void DomainImpl<BackendDataType>::sendException(const std::exception_ptr& e) noexcept {
    std::lock_guard l(_mutex);
 
    if(!_isActive) {
      // don't send exceptions if async read is off
      return;
    }
 
    _isActive = false;
    auto subDomain = _subDomain.lock();
    if(!subDomain) {
      return;
    }
 
    subDomain->sendException(e);
  }
 
  /********************************************************************************************************************/
 
  template<typename BackendDataType>
  template<typename UserDataType>
  boost::shared_ptr<AsyncNDRegisterAccessor<UserDataType>> DomainImpl<BackendDataType>::subscribe(
      RegisterPath name, size_t numberOfWords, size_t wordOffsetInRegister, AccessModeFlags flags) {
    std::lock_guard l(_mutex);
 
    auto subDomain = _subDomain.lock();
    if(!subDomain) {
      subDomain = boost::make_shared<SubDomain<BackendDataType>>(
          _backend, std::vector<size_t>({_id}), nullptr, shared_from_this());
      _subDomain = subDomain;
    }
 
    return subDomain->template subscribe<UserDataType>(name, numberOfWords, wordOffsetInRegister, flags);
  }
 
} // namespace ChimeraTK::async