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sigslot.h (21236B)

---

// sigslot.h: Signal/Slot classes
//
// Written by Sarah Thompson (sarah@telergy.com) 2002.
//
// License: Public domain. You are free to use this code however you like, with
// the proviso that the author takes on no responsibility or liability for any
// use.
//
// QUICK DOCUMENTATION
//
//        (see also the full documentation at http://sigslot.sourceforge.net/)
//
//    #define switches
//      SIGSLOT_PURE_ISO:
//        Define this to force ISO C++ compliance. This also disables all of
//        the thread safety support on platforms where it is available.
//
//      SIGSLOT_USE_POSIX_THREADS:
//        Force use of Posix threads when using a C++ compiler other than gcc
//        on a platform that supports Posix threads. (When using gcc, this is
//        the default - use SIGSLOT_PURE_ISO to disable this if necessary)
//
//      SIGSLOT_DEFAULT_MT_POLICY:
//        Where thread support is enabled, this defaults to
//        multi_threaded_global. Otherwise, the default is single_threaded.
//        #define this yourself to override the default. In pure ISO mode,
//        anything other than single_threaded will cause a compiler error.
//
//    PLATFORM NOTES
//
//      Win32:
//        On Win32, the WEBRTC_WIN symbol must be #defined. Most mainstream
//        compilers do this by default, but you may need to define it yourself
//        if your build environment is less standard. This causes the Win32
//        thread support to be compiled in and used automatically.
//
//      Unix/Linux/BSD, etc.:
//        If you're using gcc, it is assumed that you have Posix threads
//        available, so they are used automatically. You can override this (as
//        under Windows) with the SIGSLOT_PURE_ISO switch. If you're using
//        something other than gcc but still want to use Posix threads, you
//        need to #define SIGSLOT_USE_POSIX_THREADS.
//
//      ISO C++:
//        If none of the supported platforms are detected, or if
//        SIGSLOT_PURE_ISO is defined, all multithreading support is turned
//        off, along with any code that might cause a pure ISO C++ environment
//        to complain. Before you ask, gcc -ansi -pedantic won't compile this
//        library, but gcc -ansi is fine. Pedantic mode seems to throw a lot of
//        errors that aren't really there. If you feel like investigating this,
//        please contact the author.
//
//
//    THREADING MODES
//
//      single_threaded:
//        Your program is assumed to be single threaded from the point of view
//        of signal/slot usage (i.e. all objects using signals and slots are
//        created and destroyed from a single thread). Behaviour if objects are
//        destroyed concurrently is undefined (i.e. you'll get the occasional
//        segmentation fault/memory exception).
//
//      multi_threaded_global:
//        Your program is assumed to be multi threaded. Objects using signals
//        and slots can be safely created and destroyed from any thread, even
//        when connections exist. In multi_threaded_global mode, this is
//        achieved by a single global mutex (actually a critical section on
//        Windows because they are faster). This option uses less OS resources,
//        but results in more opportunities for contention, possibly resulting
//        in more context switches than are strictly necessary.
//
//      multi_threaded_local:
//        Behaviour in this mode is essentially the same as
//        multi_threaded_global, except that each signal, and each object that
//        inherits has_slots, all have their own mutex/critical section. In
//        practice, this means that mutex collisions (and hence context
//        switches) only happen if they are absolutely essential. However, on
//        some platforms, creating a lot of mutexes can slow down the whole OS,
//        so use this option with care.
//
//    USING THE LIBRARY
//
//      See the full documentation at http://sigslot.sourceforge.net/
//
// Libjingle specific:
//
// This file has been modified such that has_slots and signalx do not have to be
// using the same threading requirements. E.g. it is possible to connect a
// has_slots<single_threaded> and signal0<multi_threaded_local> or
// has_slots<multi_threaded_local> and signal0<single_threaded>.
// If has_slots is single threaded the user must ensure that it is not trying
// to connect or disconnect to signalx concurrently or data race may occur.
// If signalx is single threaded the user must ensure that disconnect, connect
// or signal is not happening concurrently or data race may occur.

#ifndef RTC_BASE_SIGSLOT_H_
#define RTC_BASE_SIGSLOT_H_

#include <stdlib.h>

#include <cstring>
#include <list>
#include <set>

// On our copy of sigslot.h, we set single threading as default.
#define SIGSLOT_DEFAULT_MT_POLICY single_threaded

#if defined(SIGSLOT_PURE_ISO) ||                   \
   (!defined(WEBRTC_WIN) && !defined(__GNUG__) && \
    !defined(SIGSLOT_USE_POSIX_THREADS))
#  define _SIGSLOT_SINGLE_THREADED
#elif defined(WEBRTC_WIN)
#  define _SIGSLOT_HAS_WIN32_THREADS
#  if !defined(WIN32_LEAN_AND_MEAN)
#    define WIN32_LEAN_AND_MEAN
#  endif
#  include "rtc_base/win32.h"
#elif (defined(__GNUG__) || defined(SIGSLOT_USE_POSIX_THREADS)) && \
   !defined(__MINGW32__)
#  define _SIGSLOT_HAS_POSIX_THREADS
#  include <pthread.h>
#else
#  define _SIGSLOT_SINGLE_THREADED
#endif

#ifndef SIGSLOT_DEFAULT_MT_POLICY
#  ifdef _SIGSLOT_SINGLE_THREADED
#    define SIGSLOT_DEFAULT_MT_POLICY single_threaded
#  else
#    define SIGSLOT_DEFAULT_MT_POLICY multi_threaded_local
#  endif
#endif

// TODO: change this namespace to rtc?
namespace sigslot {

class single_threaded {
public:
 void lock() {}
 void unlock() {}
};

#ifdef _SIGSLOT_HAS_WIN32_THREADS
// The multi threading policies only get compiled in if they are enabled.
class multi_threaded_global {
public:
 multi_threaded_global() {
   static bool isinitialised = false;

   if (!isinitialised) {
     InitializeCriticalSection(get_critsec());
     isinitialised = true;
   }
 }

 void lock() { EnterCriticalSection(get_critsec()); }

 void unlock() { LeaveCriticalSection(get_critsec()); }

private:
 CRITICAL_SECTION* get_critsec() {
   static CRITICAL_SECTION g_critsec;
   return &g_critsec;
 }
};

class multi_threaded_local {
public:
 multi_threaded_local() { InitializeCriticalSection(&m_critsec); }

 multi_threaded_local(const multi_threaded_local&) {
   InitializeCriticalSection(&m_critsec);
 }

 ~multi_threaded_local() { DeleteCriticalSection(&m_critsec); }

 void lock() { EnterCriticalSection(&m_critsec); }

 void unlock() { LeaveCriticalSection(&m_critsec); }

private:
 CRITICAL_SECTION m_critsec;
};
#endif  // _SIGSLOT_HAS_WIN32_THREADS

#ifdef _SIGSLOT_HAS_POSIX_THREADS
// The multi threading policies only get compiled in if they are enabled.
class multi_threaded_global {
public:
 void lock() { pthread_mutex_lock(get_mutex()); }
 void unlock() { pthread_mutex_unlock(get_mutex()); }

private:
 static pthread_mutex_t* get_mutex();
};

class multi_threaded_local {
public:
 multi_threaded_local() { pthread_mutex_init(&m_mutex, nullptr); }
 multi_threaded_local(const multi_threaded_local&) {
   pthread_mutex_init(&m_mutex, nullptr);
 }
 ~multi_threaded_local() { pthread_mutex_destroy(&m_mutex); }
 void lock() { pthread_mutex_lock(&m_mutex); }
 void unlock() { pthread_mutex_unlock(&m_mutex); }

private:
 pthread_mutex_t m_mutex;
};
#endif  // _SIGSLOT_HAS_POSIX_THREADS

template <class mt_policy>
class lock_block {
public:
 mt_policy* m_mutex;

 explicit lock_block(mt_policy* mtx) : m_mutex(mtx) { m_mutex->lock(); }

 ~lock_block() { m_mutex->unlock(); }
};

class _signal_base_interface;

class has_slots_interface {
private:
 typedef void (*signal_connect_t)(has_slots_interface* self,
                                  _signal_base_interface* sender);
 typedef void (*signal_disconnect_t)(has_slots_interface* self,
                                     _signal_base_interface* sender);
 typedef void (*disconnect_all_t)(has_slots_interface* self);

 const signal_connect_t m_signal_connect;
 const signal_disconnect_t m_signal_disconnect;
 const disconnect_all_t m_disconnect_all;

protected:
 has_slots_interface(signal_connect_t conn, signal_disconnect_t disc,
                     disconnect_all_t disc_all)
     : m_signal_connect(conn),
       m_signal_disconnect(disc),
       m_disconnect_all(disc_all) {}

 // Doesn't really need to be virtual, but is for backwards compatibility
 // (it was virtual in a previous version of sigslot).
 virtual ~has_slots_interface() = default;

public:
 void signal_connect(_signal_base_interface* sender) {
   m_signal_connect(this, sender);
 }

 void signal_disconnect(_signal_base_interface* sender) {
   m_signal_disconnect(this, sender);
 }

 void disconnect_all() { m_disconnect_all(this); }
};

class _signal_base_interface {
private:
 typedef void (*slot_disconnect_t)(_signal_base_interface* self,
                                   has_slots_interface* pslot);
 typedef void (*slot_duplicate_t)(_signal_base_interface* self,
                                  const has_slots_interface* poldslot,
                                  has_slots_interface* pnewslot);

 const slot_disconnect_t m_slot_disconnect;
 const slot_duplicate_t m_slot_duplicate;

protected:
 _signal_base_interface(slot_disconnect_t disc, slot_duplicate_t dupl)
     : m_slot_disconnect(disc), m_slot_duplicate(dupl) {}

 ~_signal_base_interface() = default;

public:
 void slot_disconnect(has_slots_interface* pslot) {
   m_slot_disconnect(this, pslot);
 }

 void slot_duplicate(const has_slots_interface* poldslot,
                     has_slots_interface* pnewslot) {
   m_slot_duplicate(this, poldslot, pnewslot);
 }
};

class _opaque_connection {
private:
 typedef void (*emit_t)(const _opaque_connection*);
 template <typename FromT, typename ToT>
 union union_caster {
   FromT from;
   ToT to;
 };

 emit_t pemit;
 has_slots_interface* pdest;
 // Pointers to member functions may be up to 16 bytes for virtual classes,
 // so make sure we have enough space to store it.
 unsigned char pmethod[16];

public:
 template <typename DestT, typename... Args>
 _opaque_connection(DestT* pd, void (DestT::*pm)(Args...)) : pdest(pd) {
   typedef void (DestT::*pm_t)(Args...);
   static_assert(sizeof(pm_t) <= sizeof(pmethod),
                 "Size of slot function pointer too large.");

   std::memcpy(pmethod, &pm, sizeof(pm_t));

   typedef void (*em_t)(const _opaque_connection* self, Args...);
   union_caster<em_t, emit_t> caster2;
   caster2.from = &_opaque_connection::emitter<DestT, Args...>;
   pemit = caster2.to;
 }

 has_slots_interface* getdest() const { return pdest; }

 _opaque_connection duplicate(has_slots_interface* newtarget) const {
   _opaque_connection res = *this;
   res.pdest = newtarget;
   return res;
 }

 // Just calls the stored "emitter" function pointer stored at construction
 // time.
 template <typename... Args>
 void emit(Args... args) const {
   typedef void (*em_t)(const _opaque_connection*, Args...);
   union_caster<emit_t, em_t> caster;
   caster.from = pemit;
   (caster.to)(this, args...);
 }

private:
 template <typename DestT, typename... Args>
 static void emitter(const _opaque_connection* self, Args... args) {
   typedef void (DestT::*pm_t)(Args...);
   pm_t pm;
   std::memcpy(&pm, self->pmethod, sizeof(pm_t));
   (static_cast<DestT*>(self->pdest)->*(pm))(args...);
 }
};

template <class mt_policy>
class _signal_base : public _signal_base_interface, public mt_policy {
protected:
 typedef std::list<_opaque_connection> connections_list;

 _signal_base()
     : _signal_base_interface(&_signal_base::do_slot_disconnect,
                              &_signal_base::do_slot_duplicate),
       m_current_iterator(m_connected_slots.end()) {}

 ~_signal_base() { disconnect_all(); }

private:
 _signal_base& operator=(_signal_base const& that);

public:
 _signal_base(const _signal_base& o)
     : _signal_base_interface(&_signal_base::do_slot_disconnect,
                              &_signal_base::do_slot_duplicate),
       m_current_iterator(m_connected_slots.end()) {
   lock_block<mt_policy> lock(this);
   for (const auto& connection : o.m_connected_slots) {
     connection.getdest()->signal_connect(this);
     m_connected_slots.push_back(connection);
   }
 }

 bool is_empty() {
   lock_block<mt_policy> lock(this);
   return m_connected_slots.empty();
 }

 void disconnect_all() {
   lock_block<mt_policy> lock(this);

   while (!m_connected_slots.empty()) {
     has_slots_interface* pdest = m_connected_slots.front().getdest();
     m_connected_slots.pop_front();
     pdest->signal_disconnect(static_cast<_signal_base_interface*>(this));
   }
   // If disconnect_all is called while the signal is firing, advance the
   // current slot iterator to the end to avoid an invalidated iterator from
   // being dereferenced.
   m_current_iterator = m_connected_slots.end();
 }

#if !defined(NDEBUG)
 bool connected(has_slots_interface* pclass) {
   lock_block<mt_policy> lock(this);
   connections_list::const_iterator it = m_connected_slots.begin();
   connections_list::const_iterator itEnd = m_connected_slots.end();
   while (it != itEnd) {
     if (it->getdest() == pclass) return true;
     ++it;
   }
   return false;
 }
#endif

 void disconnect(has_slots_interface* pclass) {
   lock_block<mt_policy> lock(this);
   connections_list::iterator it = m_connected_slots.begin();
   connections_list::iterator itEnd = m_connected_slots.end();

   while (it != itEnd) {
     if (it->getdest() == pclass) {
       // If we're currently using this iterator because the signal is firing,
       // advance it to avoid it being invalidated.
       if (m_current_iterator == it) {
         m_current_iterator = m_connected_slots.erase(it);
       } else {
         m_connected_slots.erase(it);
       }
       pclass->signal_disconnect(static_cast<_signal_base_interface*>(this));
       return;
     }
     ++it;
   }
 }

private:
 static void do_slot_disconnect(_signal_base_interface* p,
                                has_slots_interface* pslot) {
   _signal_base* const self = static_cast<_signal_base*>(p);
   lock_block<mt_policy> lock(self);
   connections_list::iterator it = self->m_connected_slots.begin();
   connections_list::iterator itEnd = self->m_connected_slots.end();

   while (it != itEnd) {
     connections_list::iterator itNext = it;
     ++itNext;

     if (it->getdest() == pslot) {
       // If we're currently using this iterator because the signal is firing,
       // advance it to avoid it being invalidated.
       if (self->m_current_iterator == it) {
         self->m_current_iterator = self->m_connected_slots.erase(it);
       } else {
         self->m_connected_slots.erase(it);
       }
     }

     it = itNext;
   }
 }

 static void do_slot_duplicate(_signal_base_interface* p,
                               const has_slots_interface* oldtarget,
                               has_slots_interface* newtarget) {
   _signal_base* const self = static_cast<_signal_base*>(p);
   lock_block<mt_policy> lock(self);
   connections_list::iterator it = self->m_connected_slots.begin();
   connections_list::iterator itEnd = self->m_connected_slots.end();

   while (it != itEnd) {
     if (it->getdest() == oldtarget) {
       self->m_connected_slots.push_back(it->duplicate(newtarget));
     }

     ++it;
   }
 }

protected:
 connections_list m_connected_slots;

 // Used to handle a slot being disconnected while a signal is
 // firing (iterating m_connected_slots).
 connections_list::iterator m_current_iterator;
 bool m_erase_current_iterator = false;
};

template <class mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
class has_slots : public has_slots_interface, public mt_policy {
private:
 typedef std::set<_signal_base_interface*> sender_set;
 typedef sender_set::const_iterator const_iterator;

public:
 has_slots()
     : has_slots_interface(&has_slots::do_signal_connect,
                           &has_slots::do_signal_disconnect,
                           &has_slots::do_disconnect_all) {}

 has_slots(has_slots const& o)
     : has_slots_interface(&has_slots::do_signal_connect,
                           &has_slots::do_signal_disconnect,
                           &has_slots::do_disconnect_all) {
   lock_block<mt_policy> lock(this);
   for (auto* sender : o.m_senders) {
     sender->slot_duplicate(&o, this);
     m_senders.insert(sender);
   }
 }

 ~has_slots() { this->disconnect_all(); }

private:
 has_slots& operator=(has_slots const&);

 static void do_signal_connect(has_slots_interface* p,
                               _signal_base_interface* sender) {
   has_slots* const self = static_cast<has_slots*>(p);
   lock_block<mt_policy> lock(self);
   self->m_senders.insert(sender);
 }

 static void do_signal_disconnect(has_slots_interface* p,
                                  _signal_base_interface* sender) {
   has_slots* const self = static_cast<has_slots*>(p);
   lock_block<mt_policy> lock(self);
   self->m_senders.erase(sender);
 }

 static void do_disconnect_all(has_slots_interface* p) {
   has_slots* const self = static_cast<has_slots*>(p);
   lock_block<mt_policy> lock(self);
   while (!self->m_senders.empty()) {
     std::set<_signal_base_interface*> senders;
     senders.swap(self->m_senders);
     const_iterator it = senders.begin();
     const_iterator itEnd = senders.end();

     while (it != itEnd) {
       _signal_base_interface* s = *it;
       ++it;
       s->slot_disconnect(p);
     }
   }
 }

private:
 sender_set m_senders;
};

template <class mt_policy, typename... Args>
class signal_with_thread_policy : public _signal_base<mt_policy> {
private:
 typedef _signal_base<mt_policy> base;

protected:
 typedef typename base::connections_list connections_list;

public:
 signal_with_thread_policy() = default;

 template <class desttype>
 void connect(desttype* pclass, void (desttype::*pmemfun)(Args...)) {
   lock_block<mt_policy> lock(this);
   this->m_connected_slots.push_back(_opaque_connection(pclass, pmemfun));
   pclass->signal_connect(static_cast<_signal_base_interface*>(this));
 }

 void emit(Args... args) {
   lock_block<mt_policy> lock(this);
   this->m_current_iterator = this->m_connected_slots.begin();
   while (this->m_current_iterator != this->m_connected_slots.end()) {
     _opaque_connection const& conn = *this->m_current_iterator;
     ++(this->m_current_iterator);
     conn.emit<Args...>(args...);
   }
 }

 void operator()(Args... args) { emit(args...); }
};

// Alias with default thread policy. Needed because both default arguments
// and variadic template arguments must go at the end of the list, so we
// can't have both at once.
template <typename... Args>
using signal = signal_with_thread_policy<SIGSLOT_DEFAULT_MT_POLICY, Args...>;

// The previous verion of sigslot didn't use variadic templates, so you would
// need to write "sigslot::signal2<Arg1, Arg2>", for example.
// Now you can just write "sigslot::signal<Arg1, Arg2>", but these aliases
// exist for backwards compatibility.
template <typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal0 = signal_with_thread_policy<mt_policy>;

template <typename A1, typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal1 = signal_with_thread_policy<mt_policy, A1>;

template <typename A1, typename A2,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal2 = signal_with_thread_policy<mt_policy, A1, A2>;

template <typename A1, typename A2, typename A3,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal3 = signal_with_thread_policy<mt_policy, A1, A2, A3>;

template <typename A1, typename A2, typename A3, typename A4,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal4 = signal_with_thread_policy<mt_policy, A1, A2, A3, A4>;

template <typename A1, typename A2, typename A3, typename A4, typename A5,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal5 = signal_with_thread_policy<mt_policy, A1, A2, A3, A4, A5>;

template <typename A1, typename A2, typename A3, typename A4, typename A5,
         typename A6, typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal6 = signal_with_thread_policy<mt_policy, A1, A2, A3, A4, A5, A6>;

template <typename A1, typename A2, typename A3, typename A4, typename A5,
         typename A6, typename A7,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal7 =
   signal_with_thread_policy<mt_policy, A1, A2, A3, A4, A5, A6, A7>;

template <typename A1, typename A2, typename A3, typename A4, typename A5,
         typename A6, typename A7, typename A8,
         typename mt_policy = SIGSLOT_DEFAULT_MT_POLICY>
using signal8 =
   signal_with_thread_policy<mt_policy, A1, A2, A3, A4, A5, A6, A7, A8>;

}  // namespace sigslot

#endif  // RTC_BASE_SIGSLOT_H_