poller.cpp

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/*
 * Zth (libzth), a cooperative userspace multitasking library.
 * Copyright (C) 2019-2022  Jochem Rutgers
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */
 
#include <libzth/poller.h>
 
namespace zth {
 
 
// PollerInterface
//
 
#if __cplusplus >= 201103L
int PollerInterface::add(std::initializer_list<std::reference_wrapper<Pollable>> l) noexcept
{
        try {
                reserve(l.size());
        } catch(...) {
                return ENOMEM;
        }
 
        int res = 0;
        size_t count = 0;
 
        for(Pollable& p : l) {
                if((res = add(p))) {
                        // Rollback.
                        for(auto const* it = l.begin(); it != l.end() && count > 0; ++it, count--)
                                remove(*it);
                        break;
                }
 
                // Success.
                count++;
        }
 
        return res;
}
#endif // C++11
 
 
 
#ifdef ZTH_HAVE_LIBZMQ
// ZmqPoller
//
 
ZmqPoller::ZmqPoller()
{
        this->setName("zth::ZmqPoller");
}
 
ZmqPoller::~ZmqPoller() is_default
 
int ZmqPoller::init(Pollable const& p, zmq_pollitem_t& item) noexcept
{
        // Zth only has PollableFds, so casting is safe.
        // NOLINTNEXTLINE(cppcoreguidelines-pro-type-static-cast-downcast)
        PollableFd const& pfd = static_cast<PollableFd const&>(p);
 
        item.socket = pfd.socket;
        item.fd = pfd.fd;
 
        item.events = 0;
        if((pfd.events.test(Pollable::PollInIndex)))
                item.events |= ZMQ_POLLIN;
        if((pfd.events.test(Pollable::PollOutIndex)))
                item.events |= ZMQ_POLLOUT;
        return 0;
}
 
int ZmqPoller::doPoll(int timeout_ms, typename base::PollItemList& items) noexcept
{
        zth_assert(items.size() <= (size_t)std::numeric_limits<int>::max());
        int res = zmq_poll(items.data(), (int)items.size(), timeout_ms);
        if(res < 0)
                return zmq_errno();
        if(res == 0)
                // Timeout.
                return 0;
 
        for(size_t i = 0; res > 0 && i < items.size(); i++) {
                zmq_pollitem_t const& item = items[i];
                Pollable::Events revents = 0;
 
                if(item.revents) {
                        res--;
 
                        if(item.revents & ZMQ_POLLIN) // NOLINT(hicpp-signed-bitwise)
                                revents |= Pollable::PollIn;
                        if(item.revents & ZMQ_POLLOUT) // NOLINT(hicpp-signed-bitwise)
                                revents |= Pollable::PollOut;
                        if(item.revents & ZMQ_POLLERR) // NOLINT(hicpp-signed-bitwise)
                                revents |= Pollable::PollErr;
                }
 
                this->event(revents, i);
        }
 
        return 0;
}
 
#elif defined(ZTH_HAVE_POLL)
// PollPoller
//
 
PollPoller::PollPoller()
{
        setName("zth::PollPoller");
}
 
PollPoller::~PollPoller()
{
        clear();
}
 
int PollPoller::init(Pollable const& p, struct pollfd& item) noexcept
{
        // Zth only has PollableFds, so casting is safe.
        // NOLINTNEXTLINE(cppcoreguidelines-pro-type-static-cast-downcast)
        PollableFd const& pfd = static_cast<PollableFd const&>(p);
 
        item.fd = pfd.fd;
 
        item.events = 0;
        if((pfd.events.test(Pollable::PollInIndex)))
                item.events |= POLLIN;
        if((pfd.events.test(Pollable::PollOutIndex)))
                item.events |= POLLOUT;
        if((pfd.events.test(Pollable::PollPriIndex)))
                item.events |= POLLPRI;
        if((pfd.events.test(Pollable::PollHupIndex)))
                item.events |= POLLHUP;
 
        return 0;
}
 
int PollPoller::doPoll(int timeout_ms, base::PollItemList& items) noexcept
{
        int res = ::poll(items.data(), items.size(), timeout_ms);
        if(res < 0)
                return errno;
        if(res == 0)
                // Timeout.
                return 0;
 
        for(size_t i = 0; res > 0 && i < items.size(); i++) {
                struct pollfd const& item = items[i];
                Pollable::Events revents = 0;
 
                if(item.revents) {
                        res--;
 
                        if(item.revents & POLLIN)
                                revents |= Pollable::PollIn;
                        if(item.revents & POLLOUT)
                                revents |= Pollable::PollOut;
                        if(item.revents & POLLERR)
                                revents |= Pollable::PollErr;
                        if(item.revents & POLLPRI)
                                revents |= Pollable::PollPri;
                        if(item.revents & POLLHUP)
                                revents |= Pollable::PollHup;
                }
 
                event(revents, i);
        }
 
        return 0;
}
 
 
#else
// NoPoller
//
 
NoPoller::NoPoller()
{
        setName("zth::NoPoller");
}
 
NoPoller::~NoPoller() is_default
 
int NoPoller::init(Pollable const& UNUSED_PAR(p), int& UNUSED_PAR(item)) noexcept
{
        return EINVAL;
}
 
int NoPoller::doPoll(int UNUSED_PAR(timeout_ms), base::PollItemList& UNUSED_PAR(items)) noexcept
{
        return ENOSYS;
}
 
#endif // Poller method
 
 
 
// PollerClient
//
 
PollerClient::PollerClient()
{
        this->setName("zth::PollerClient");
}
 
#if __cplusplus >= 201103L
PollerClient::PollerClient(std::initializer_list<std::reference_wrapper<Pollable>> l)
{
        errno = add(l);
 
#       ifdef __cpp_exceptions
        switch(errno) {
        case 0:
                break;
        case ENOMEM:
                throw std::bad_alloc();
        default:
                throw std::runtime_error("");
        }
#       endif
}
#endif
 
PollerClient::~PollerClient() is_default
 
void PollerClient::reserve(size_t more)
{
        m_pollables.reserve(m_pollables.size() + more);
        m_result.reserve(m_pollables.capacity());
}
 
int PollerClient::add(Pollable& p) noexcept
{
        try {
                m_result.reserve(m_pollables.size() + 1u);
                m_pollables.push_back(&p);
                zth_dbg(io, "[%s] poll %p for events 0x%lu", id_str(), &p, p.events.to_ulong());
                return 0;
        } catch(...) {
                return ENOMEM;
        }
}
 
int PollerClient::remove(Pollable& p) noexcept
{
        for(size_t i = m_pollables.size(); i > 0; i--) {
                Pollable*& pi = m_pollables[i - 1u];
                if(pi == &p) {
                        pi = m_pollables.back();
                        m_pollables.pop_back();
                        return 0;
                }
        }
 
        return EAGAIN;
}
 
PollerClient::Result const& PollerClient::poll(int timeout_ms) noexcept
{
        m_result.clear();
 
        if(m_pollables.empty()) {
                errno = EINVAL;
                return m_result;
        }
 
        Waiter& waiter = currentWorker().waiter();
        PollerServerBase& p = waiter.poller();
 
        // Add all our pollables to the server.
        for(size_t i = 0; i < m_pollables.size(); i++)
                p.add(*m_pollables[i], this);
 
        // Go do the poll.
        zth_dbg(io, "[%s] polling %u items for %d ms", id_str(), (unsigned)m_pollables.size(),
                timeout_ms);
 
        // First try, in the current fiber's context.
        m_wait = TimedWaitable();
        int res = p.poll(0);
 
        if(!m_result.empty()) { // NOLINT(bugprone-branch-clone)
                                // Completed already.
        } else if(res && res != EAGAIN) {
                // Completed with an error.
        } else if(timeout_ms == 0) {
                // Just tried. Got nothing, apparently.
        } else if(timeout_ms < 0) {
                // Wait for the event callback.
                zth_dbg(io, "[%s] hand-off to server", id_str());
                m_wait.setFiber(currentFiber());
                suspend();
        } else {
                zth_dbg(io, "[%s] hand-off to server with timeout", id_str());
                m_wait = TimedWaitable(
                        Timestamp::now()
                        + TimeInterval(timeout_ms / 1000L, (timeout_ms * 1000000L) % 1000000000L));
                waitUntil(m_wait);
        }
 
        // Remove our pollables from the server.
        for(size_t i = m_pollables.size(); i > 0; i--)
                p.remove(*m_pollables[i - 1u], this);
 
        // m_result got populated by event().
        if(m_result.empty() && !res)
                res = EAGAIN;
 
        if(res)
                zth_dbg(io, "[%s] poll returned %s", id_str(), err(res).c_str());
        else
                zth_dbg(io, "[%s] poll returned %u pollable(s)", id_str(),
                        (unsigned)m_result.size());
 
        errno = res;
        return m_result;
}
 
void PollerClient::event(Pollable& p) noexcept
{
        m_result.push_back(&p);
 
        if(!m_wait.timeout().isNull()) {
                // Managed by the waiter
                currentWorker().waiter().wakeup(m_wait);
        } else if(m_wait.hasFiber()) {
                // Just suspended.
                resume(m_wait.fiber());
        }
}
 
bool PollerClient::empty() const noexcept
{
        return m_pollables.empty();
}
 
} // namespace zth