resourceToken.cpp

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/**
 * @file
 * @ingroup daq
 * @copyright (c) Copyright ESO 2023
 * All Rights Reserved
 * ESO (eso.org) is an Intergovernmental Organisation, and therefore special legal conditions apply.
 */
#include <daq/resourceToken.hpp>
 
#include <log4cplus/loggingmacros.h>
 
namespace daq {
ResourceToken::ResourceToken(Resource* resource) noexcept : m_resource(resource) {
}
 
ResourceToken::~ResourceToken() noexcept {
    if (m_resource) {
        m_resource->Release();
    }
}
ResourceToken::ResourceToken(ResourceToken&& rhs) noexcept : m_resource(nullptr) {
    *this = std::move(rhs);
}
 
ResourceToken& ResourceToken::operator=(ResourceToken&& rhs) noexcept {
    if (m_resource) {
        m_resource->Release();
    }
    m_resource = rhs.m_resource;
    rhs.m_resource = nullptr;
    return *this;
}
 
std::optional<ResourceToken> Resource::Acquire() noexcept {
    if (HasResource()) {
        m_used++;
        return ResourceToken(this);
    }
    return {};
}
 
boost::future<ResourceToken> Resource::AsyncAcquire() noexcept {
    auto maybe_token = Acquire();
    if (maybe_token) {
        return boost::make_ready_future<ResourceToken>(*std::move(maybe_token));
    } else {
        auto& ref = m_promises.emplace();
        return ref.get_future();
    }
}
 
boost::signals2::connection Resource::Connect(Signal::slot_type const& slot) {
    return m_signal.connect(slot);
}
 
void Resource::Release() noexcept {
    m_used--;
 
    while (HasResource() && !m_promises.empty()) {
        // If future invokes completion function that releases resource we need to protected against
        // recursive calls.
        auto promise = std::move(m_promises.front());
        m_promises.pop();
        m_used++;
        promise.set_value(ResourceToken(this));  // may trigger recursive call
    }
 
    // If we still have resources signal slots
    if (HasResource()) {
        m_signal();
    }
}
}  // namespace daq