srs/trunk/3rdparty/srt-1-fit/srtcore/epoll.h

/*
 * SRT - Secure, Reliable, Transport
 * Copyright (c) 2018 Haivision Systems Inc.
 * 
 * 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 http://mozilla.org/MPL/2.0/.
 * 
 */

/*****************************************************************************
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  and/or other materials provided with the distribution.

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/*****************************************************************************
written by
   Yunhong Gu, last updated 08/20/2010
modified by
   Haivision Systems Inc.
*****************************************************************************/

#ifndef INC_SRT_EPOLL_H
#define INC_SRT_EPOLL_H


#include <map>
#include <set>
#include <list>
#include "udt.h"

namespace srt
{

class CUDT;
class CRendezvousQueue;
class CUDTGroup;


class CEPollDesc
{
#ifdef __GNUG__
   const int m_iID;                                // epoll ID
#else
   const int m_iID SRT_ATR_UNUSED;                 // epoll ID
#endif
   struct Wait;

   struct Notice: public SRT_EPOLL_EVENT
   {
       Wait* parent;

       Notice(Wait* p, SRTSOCKET sock, int ev): parent(p)
       {
           fd = sock;
           events = ev;
       }
   };

   /// The type for `m_USockEventNotice`, the pair contains:
   /// * The back-pointer to the subscriber object for which this event notice serves
   /// * The events currently being on
   typedef std::list<Notice> enotice_t;

   struct Wait
   {
       /// Events the subscriber is interested with. Only those will be
       /// regarded when updating event flags.
       int32_t watch;

       /// Which events should be edge-triggered. When the event isn't
       /// mentioned in `watch`, this bit flag is disregarded. Otherwise
       /// it means that the event is to be waited for persistent state
       /// if this flag is not present here, and for edge trigger, if
       /// the flag is present here.
       int32_t edge;

       /// The current persistent state. This is usually duplicated in
       /// a dedicated state object in `m_USockEventNotice`, however the state
       /// here will stay forever as is, regardless of the edge/persistent
       /// subscription mode for the event.
       int32_t state;

       /// The iterator to `m_USockEventNotice` container that contains the
       /// event notice object for this subscription, or the value from
       /// `nullNotice()` if there is no such object.
       enotice_t::iterator notit;

       Wait(explicit_t<int32_t> sub, explicit_t<int32_t> etr, enotice_t::iterator i)
           :watch(sub)
           ,edge(etr)
           ,state(0)
           ,notit(i)
       {
       }

       int edgeOnly() { return edge & watch; }

       /// Clear all flags for given direction from the notices
       /// and subscriptions, and checks if this made the event list
       /// for this watch completely empty.
       /// @param direction event type that has to be cleared
       /// @return true, if this cleared the last event (the caller
       /// want to remove the subscription for this socket)
       bool clear(int32_t direction)
       {
           if (watch & direction)
           {
               watch &= ~direction;
               edge &= ~direction;
               state &= ~direction;

               return watch == 0;
           }

           return false;
       }
   };

   typedef std::map<SRTSOCKET, Wait> ewatch_t;

#if ENABLE_HEAVY_LOGGING
std::string DisplayEpollWatch();
#endif

   /// Sockets that are subscribed for events in this eid.
   ewatch_t m_USockWatchState;

   /// Objects representing changes in SRT sockets.
   /// Objects are removed from here when an event is registerred as edge-triggered.
   /// Otherwise it is removed only when all events as per subscription
   /// are no longer on.
   enotice_t m_USockEventNotice;

   // Special behavior
   int32_t m_Flags;

   enotice_t::iterator nullNotice() { return m_USockEventNotice.end(); }

   // Only CEPoll class should have access to it.
   // Guarding private access to the class is not necessary
   // within the epoll module.
   friend class CEPoll;

   CEPollDesc(int id, int localID)
       : m_iID(id)
       , m_Flags(0)
       , m_iLocalID(localID)
    {
    }

   static const int32_t EF_NOCHECK_EMPTY = 1 << 0;
   static const int32_t EF_CHECK_REP = 1 << 1;

   int32_t flags() const { return m_Flags; }
   bool flags(int32_t f) const { return (m_Flags & f) != 0; }
   void set_flags(int32_t flg) { m_Flags |= flg; }
   void clr_flags(int32_t flg) { m_Flags &= ~flg; }

   // Container accessors for ewatch_t.
   bool watch_empty() const { return m_USockWatchState.empty(); }
   Wait* watch_find(SRTSOCKET sock)
   {
       ewatch_t::iterator i = m_USockWatchState.find(sock);
       if (i == m_USockWatchState.end())
           return NULL;
       return &i->second;
   }

   // Container accessors for enotice_t.
   enotice_t::iterator enotice_begin() { return m_USockEventNotice.begin(); }
   enotice_t::iterator enotice_end() { return m_USockEventNotice.end(); }
   enotice_t::const_iterator enotice_begin() const { return m_USockEventNotice.begin(); }
   enotice_t::const_iterator enotice_end() const { return m_USockEventNotice.end(); }
   bool enotice_empty() const { return m_USockEventNotice.empty(); }

   const int m_iLocalID;                           // local system epoll ID
   std::set<SYSSOCKET> m_sLocals;            // set of local (non-UDT) descriptors

   std::pair<ewatch_t::iterator, bool> addWatch(SRTSOCKET sock, explicit_t<int32_t> events, explicit_t<int32_t> et_events)
   {
        return m_USockWatchState.insert(std::make_pair(sock, Wait(events, et_events, nullNotice())));
   }

   void addEventNotice(Wait& wait, SRTSOCKET sock, int events)
   {
       // `events` contains bits to be set, so:
       //
       // 1. If no notice object exists, add it exactly with `events`.
       // 2. If it exists, only set the bits from `events`.
       // ASSUME: 'events' is not 0, that is, we have some readiness

       if (wait.notit == nullNotice()) // No notice object
       {
           // Add new event notice and bind to the wait object.
           m_USockEventNotice.push_back(Notice(&wait, sock, events));
           wait.notit = --m_USockEventNotice.end();

           return;
       }

       // We have an existing event notice, so update it
       wait.notit->events |= events;
   }

   // This function only updates the corresponding event notice object
   // according to the change in the events.
   void updateEventNotice(Wait& wait, SRTSOCKET sock, int events, bool enable)
   {
       if (enable)
       {
           addEventNotice(wait, sock, events);
       }
       else
       {
           removeExcessEvents(wait, ~events);
       }
   }

   void removeSubscription(SRTSOCKET u)
   {
       std::map<SRTSOCKET, Wait>::iterator i = m_USockWatchState.find(u);
       if (i == m_USockWatchState.end())
           return;

       if (i->second.notit != nullNotice())
       {
           m_USockEventNotice.erase(i->second.notit);
           // NOTE: no need to update the Wait::notit field
           // because the Wait object is about to be removed anyway.
       }
       m_USockWatchState.erase(i);
   }

   void clearAll()
   {
       m_USockEventNotice.clear();
       m_USockWatchState.clear();
   }

   void removeExistingNotices(Wait& wait)
   {
       m_USockEventNotice.erase(wait.notit);
       wait.notit = nullNotice();
   }

   void removeEvents(Wait& wait)
   {
       if (wait.notit == nullNotice())
           return;
       removeExistingNotices(wait);
   }

   // This function removes notices referring to
   // events that are NOT present in @a nevts, but
   // may be among subscriptions and therefore potentially
   // have an associated notice.
   void removeExcessEvents(Wait& wait, int nevts)
   {
       // Update the event notice, should it exist
       // If the watch points to a null notice, there's simply
       // no notice there, so nothing to update or prospectively
       // remove - but may be something to add.
       if (wait.notit == nullNotice())
           return;

       // `events` contains bits to be cleared.
       // 1. If there is no notice event, do nothing - clear already.
       // 2. If there is a notice event, update by clearing the bits
       // 2.1. If this made resulting state to be 0, also remove the notice.

       const int newstate = wait.notit->events & nevts;
       if (newstate)
       {
           wait.notit->events = newstate;
       }
       else
       {
           // If the new state is full 0 (no events),
           // then remove the corresponding notice object
           removeExistingNotices(wait);
       }
   }

   bool checkEdge(enotice_t::iterator i)
   {
       // This function should check if this event was subscribed
       // as edge-triggered, and if so, clear the event from the notice.
       // Update events and check edge mode at the subscriber
       i->events &= ~i->parent->edgeOnly();
       if(!i->events)
       {
           removeExistingNotices(*i->parent);
           return true;
       }
       return false;
   }

   /// This should work in a loop around the notice container of
   /// the given eid container and clear out the notice for
   /// particular event type. If this has cleared effectively the
   /// last existing event, it should return the socket id
   /// so that the caller knows to remove it also from subscribers.
   ///
   /// @param i iterator in the notice container
   /// @param event event type to be cleared
   /// @retval (socket) Socket to be removed from subscriptions
   /// @retval SRT_INVALID_SOCK Nothing to be done (associated socket
   ///         still has other subscriptions)
   SRTSOCKET clearEventSub(enotice_t::iterator i, int event)
   {
       // We need to remove the notice and subscription
       // for this event. The 'i' iterator is safe to
       // delete, even indirectly.

       // This works merely like checkEdge, just on request to clear the
       // identified event, if found.
       if (i->events & event)
       {
           // The notice has a readiness flag on this event.
           // This means that there exists also a subscription.
           Wait* w = i->parent;
           if (w->clear(event))
               return i->fd;
       }

       return SRT_INVALID_SOCK;
   }
};

class CEPoll
{
friend class srt::CUDT;
friend class srt::CUDTGroup;
friend class srt::CRendezvousQueue;

public:
   CEPoll();
   ~CEPoll();

public: // for CUDTUnited API

   /// create a new EPoll.
   /// @return new EPoll ID if success, otherwise an error number.
   int create(CEPollDesc** ppd = 0);


   /// delete all user sockets (SRT sockets) from an EPoll
   /// @param [in] eid EPoll ID.
   /// @return 0 
   int clear_usocks(int eid);

   /// add a system socket to an EPoll.
   /// @param [in] eid EPoll ID.
   /// @param [in] s system Socket ID.
   /// @param [in] events events to watch.
   /// @return 0 if success, otherwise an error number.

   int add_ssock(const int eid, const SYSSOCKET& s, const int* events = NULL);

   /// remove a system socket event from an EPoll; socket will be removed if no events to watch.
   /// @param [in] eid EPoll ID.
   /// @param [in] s system socket ID.
   /// @return 0 if success, otherwise an error number.

   int remove_ssock(const int eid, const SYSSOCKET& s);
   /// update a UDT socket events from an EPoll.
   /// @param [in] eid EPoll ID.
   /// @param [in] u UDT socket ID.
   /// @param [in] events events to watch.
   /// @return 0 if success, otherwise an error number.

   int update_usock(const int eid, const SRTSOCKET& u, const int* events);

   /// update a system socket events from an EPoll.
   /// @param [in] eid EPoll ID.
   /// @param [in] u UDT socket ID.
   /// @param [in] events events to watch.
   /// @return 0 if success, otherwise an error number.

   int update_ssock(const int eid, const SYSSOCKET& s, const int* events = NULL);

   /// wait for EPoll events or timeout.
   /// @param [in] eid EPoll ID.
   /// @param [out] readfds UDT sockets available for reading.
   /// @param [out] writefds UDT sockets available for writing.
   /// @param [in] msTimeOut timeout threshold, in milliseconds.
   /// @param [out] lrfds system file descriptors for reading.
   /// @param [out] lwfds system file descriptors for writing.
   /// @return number of sockets available for IO.

   int wait(const int eid, std::set<SRTSOCKET>* readfds, std::set<SRTSOCKET>* writefds, int64_t msTimeOut, std::set<SYSSOCKET>* lrfds, std::set<SYSSOCKET>* lwfds);

   typedef std::map<SRTSOCKET, int> fmap_t;

   /// Lightweit and more internal-reaching version of `uwait` for internal use only.
   /// This function wait for sockets to be ready and reports them in `st` map.
   ///
   /// @param d the internal structure of the epoll container
   /// @param st output container for the results: { socket_type, event }
   /// @param msTimeOut timeout after which return with empty output is allowed
   /// @param report_by_exception if true, errors will result in exception intead of returning -1
   /// @retval -1 error occurred
   /// @retval >=0 number of ready sockets (actually size of `st`)
   int swait(CEPollDesc& d, fmap_t& st, int64_t msTimeOut, bool report_by_exception = true);

   /// Empty subscription check - for internal use only.
   bool empty(const CEPollDesc& d) const;

   /// Reports which events are ready on the given socket.
   /// @param mp socket event map retirned by `swait`
   /// @param sock which socket to ask
   /// @return event flags for given socket, or 0 if none
   static int ready(const fmap_t& mp, SRTSOCKET sock)
   {
       fmap_t::const_iterator y = mp.find(sock);
       if (y == mp.end())
           return 0;
       return y->second;
   }

   /// Reports whether socket is ready for given event.
   /// @param mp socket event map retirned by `swait`
   /// @param sock which socket to ask
   /// @param event which events it should be ready for
   /// @return true if the given socket is ready for given event
   static bool isready(const fmap_t& mp, SRTSOCKET sock, SRT_EPOLL_OPT event)
   {
       return (ready(mp, sock) & event) != 0;
   }

   // Could be a template directly, but it's now hidden in the imp file.
   void clear_ready_usocks(CEPollDesc& d, int direction);

   /// wait for EPoll events or timeout optimized with explicit EPOLL_ERR event and the edge mode option.
   /// @param [in] eid EPoll ID.
   /// @param [out] fdsSet array of user socket events (SRT_EPOLL_IN | SRT_EPOLL_OUT | SRT_EPOLL_ERR).
   /// @param [int] fdsSize of fds array
   /// @param [in] msTimeOut timeout threshold, in milliseconds.
   /// @return total of available events in the epoll system (can be greater than fdsSize)

   int uwait(const int eid, SRT_EPOLL_EVENT* fdsSet, int fdsSize, int64_t msTimeOut);

   /// close and release an EPoll.
   /// @param [in] eid EPoll ID.
   /// @return 0 if success, otherwise an error number.

   int release(const int eid);

public: // for CUDT to acknowledge IO status

   /// Update events available for a UDT socket. At the end this function
   /// counts the number of updated EIDs with given events.
   /// @param [in] uid UDT socket ID.
   /// @param [in] eids EPoll IDs to be set
   /// @param [in] events Combination of events to update
   /// @param [in] enable true -> enable, otherwise disable
   /// @return -1 if invalid events, otherwise the number of changes

   int update_events(const SRTSOCKET& uid, std::set<int>& eids, int events, bool enable);

   int setflags(const int eid, int32_t flags);

private:
   int m_iIDSeed;                            // seed to generate a new ID
   srt::sync::Mutex m_SeedLock;

   std::map<int, CEPollDesc> m_mPolls;       // all epolls
   mutable srt::sync::Mutex m_EPollLock;
};

#if ENABLE_HEAVY_LOGGING
std::string DisplayEpollResults(const std::map<SRTSOCKET, int>& sockset);
#endif

} // namespace srt


#endif