成功的微网站,wordpress购物分享主题,注册网站的好处,济宁市中网站建设大家#xff0c;我是东风#xff0c;今天抽点时间整理一下我很久前关注的一个不错的库#xff0c;可以支持我们在使用标准C的时候使用信号槽机制进行观察者模式设计#xff0c;sigslot 官网#xff1a; http://sigslot.sourceforge.net/ 本文较为详尽探讨了一种观察者模… 大家我是东风今天抽点时间整理一下我很久前关注的一个不错的库可以支持我们在使用标准C的时候使用信号槽机制进行观察者模式设计sigslot 官网 http://sigslot.sourceforge.net/ 本文较为详尽探讨了一种观察者模式的精妙实现方式即2002年由Sarah Thompson匠心设计的sigslot库。该库以其高效、灵活的特点在信号与槽的连接管理上展现出卓越性能成为事件驱动编程领域中的一大亮点。
1.sigslot 类结构 其中以 _signal_base_interface 为基类的派生系列主要实现信号的链接与触发机制以 has_slots_interface 为基类的派生系列主要实现槽对象提供信号操作的对象mt_policy、lock_block 则主要实现类似std::lock_guard的锁机制确保线程安全。此外很重要的一个类 _opaque_connection它是槽对象的逻辑存储节点在一定程度上解耦了信号与槽的直接联系。
2.源码疑问注解
2.1.信号与槽 //template class mt_policy
//class _signal_base
typedef std::list_opaque_connection connections_list;connections_list m_connected_slots; //template class mt_policy SIGSLOT_DEFAULT_MT_POLICY
//class has_slots
typedef std::set_signal_base_interface* sender_set;sender_set m_senders;
可以这样理解一个信号可以触发多个槽回调同样一个槽对象可以被多个信号触发。
2.2.函数指针 cast 肯定不少人会对_opaque_connection的union实现函数指针 cast 表示疑问
template typename FromT, typename ToT
union union_caster {FromT from;ToT to;
}; 我先给出自己的理解union_caster 实现将 FromT 类型转成 ToT。其中本质是利用以下两个性质 1 union 同一时刻只能存储一个值要么是 from要么是 to 2函数指针在同一平台上的字节大小是一样的 基于这两点那么执行下列代码时会有以下效果见代码
template typename FromT, typename ToT
union union_caster {FromT from;ToT to;
};void fun_t(int a)
{std::cout fun_t a std::endl;
}void fun_f(int a,int b)
{std::cout fun_f a , b std::endl;
}int main()
{typedef void (*emit_t)(int a);typedef void (*em_t)(int a, int b);union_casterem_t, emit_t caster2; // em_t, emit_tcaster2.from fun_f;//此时只看数值caster2.to caster2.from fun_femit_t pemit caster2.to;union_casteremit_t,em_t caster; // emit_t,em_t 巧妙完成类型转换caster.from pemit; //caster的from是caster2的to(caster.to)(30, 20); //caster的to是caster2的from因此这里等价 fun_f(30, 20)//验证想法std::cout sizeof fun_t(): sizeof(fun_t) sizeof fun_t(): sizeof(fun_f) std::endl;std::cout caster2.from: caster2.from caster2.to: caster2.to std::endl;std::cout caster.from: caster.from caster.to: caster.to std::endl;getchar();return 0;
} 3.库使用
这里我们先给一个常规的应用可以参照作者示例
#include sigslot.h
#include iostreamusing namespace sigslot;class Switch
{
public:Switch(){}~Switch(){}public:signal1int ToggleLight;};class Light : public has_slots
{
public:Light() {};~Light() {};public:void TurnState(int a){std::cout Light on/off a std::endl;}};int main()
{Switch s;Light l;s.ToggleLight.connect(l,Light::TurnState);//l.signal_disconnect((s.ToggleLight));//l.disconnect_all();//s.ToggleLight.disconnect(l);s.ToggleLight.emit(1000);//s.ToggleLight.emit(1000);getchar();return 0;
} 我认为只需搞明白connect()即可其他行为就显而易见了。通过调试跟踪我们可以发现connect() 大概流程为 很显然connect其实就是完成 m_senders 集合和 m_connected_slots 链表的更新后续 emit() 、 disconnect()等等操作都是基于这两个数据结构来开展的。举个例子当信号对象执行emit()时不用查阅代码我们都可以知道流程大概是信号对象遍历 m_connected_slots 针对每一个 _opaque_connection回调它事先存储的槽对象成员方法。 TIPS: 1 has_slots 的 signal_connect()、signal_disconnect()成员只是操作了 m_senders并没有更新 m_connected_slotsdisconnect_all() 成员更新了 m_senders 和 m_connected_slots 2signal 的 connect()、disconnect() 等基本所有类似成员方法里都同时更新了 m_senders和 m_connected_slots。 若有不对提醒我啦 附录sigslot 源码
//头文件sigslot.h
//
// sigslot.h: Signal/Slot classes
//
// Written by Sarah Thompson (sarahtelergy.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 youre 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 youre 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 wont compile this
// library, but gcc -ansi is fine. Pedantic mode seems to throw a lot of
// errors that arent 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. youll 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_slotssingle_threaded and signal0multi_threaded_local or
// has_slotsmulti_threaded_local and signal0single_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_THIRD_PARTY_SIGSLOT_SIGSLOT_H_
#define RTC_BASE_THIRD_PARTY_SIGSLOT_SIGSLOT_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
#include windows.h
#elif defined(__GNUG__) || defined(SIGSLOT_USE_POSIX_THREADS)
#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//
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_THREADStemplate class mt_policy
class lock_block {public:mt_policy* m_mutex;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) {}// Doesnt really need to be virtual, but is for backwards compatibility// (it was virtual in a previous version of sigslot).virtual ~has_slots_interface() {}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() {}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 ToTunion union_caster {FromT from;ToT to;};emit_t pemit;has_slots_interface* pdest;// Pointers to member functions may be up to 16 bytes (24 bytes for MSVC)// for virtual classes, so make sure we have enough space to store it.
#if defined(_MSC_VER) !defined(__clang__)unsigned char pmethod[24];
#elseunsigned char pmethod[16];
#endifpublic: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_casterem_t, emit_t caster2;caster2.from _opaque_connection::emitterDestT, 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... Argsvoid emit(Args... args) const {typedef void (*em_t)(const _opaque_connection*, Args...);union_casteremit_t, em_t caster;caster.from pemit;(caster.to)(this, args...);}private:template typename DestT, typename... Argsstatic void emitter(const _opaque_connection* self, Args... args) {typedef void (DestT::*pm_t)(Args...);pm_t pm;static_assert(sizeof(pm_t) sizeof(pmethod),Size of slot function pointer too large.);std::memcpy(pm, self-pmethod, sizeof(pm_t));(static_castDestT*(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_blockmt_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_blockmt_policy lock(this);return m_connected_slots.empty();}void disconnect_all() {lock_blockmt_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_blockmt_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;}
#endifvoid disconnect(has_slots_interface* pclass) {lock_blockmt_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 were 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_blockmt_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 were 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_blockmt_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_blockmt_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_casthas_slots*(p);lock_blockmt_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_casthas_slots*(p);lock_blockmt_policy lock(self);self-m_senders.erase(sender);}static void do_disconnect_all(has_slots_interface* p) {has_slots* const self static_casthas_slots*(p);lock_blockmt_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_basemt_policy {private:typedef _signal_basemt_policy base;protected:typedef typename base::connections_list connections_list;public:signal_with_thread_policy() {}template class desttypevoid connect(desttype* pclass, void (desttype::*pmemfun)(Args...)) {lock_blockmt_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_blockmt_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.emitArgs...(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
// cant have both at once.
template typename... Args
using signal signal_with_thread_policySIGSLOT_DEFAULT_MT_POLICY, Args...;// The previous verion of sigslot didnt use variadic templates, so you would
// need to write sigslot::signal2Arg1, Arg2, for example.
// Now you can just write sigslot::signalArg1, Arg2, but these aliases
// exist for backwards compatibility.
template typename mt_policy SIGSLOT_DEFAULT_MT_POLICY
using signal0 signal_with_thread_policymt_policy;template typename A1, typename mt_policy SIGSLOT_DEFAULT_MT_POLICY
using signal1 signal_with_thread_policymt_policy, A1;template typename A1,typename A2,typename mt_policy SIGSLOT_DEFAULT_MT_POLICY
using signal2 signal_with_thread_policymt_policy, A1, A2;template typename A1,typename A2,typename A3,typename mt_policy SIGSLOT_DEFAULT_MT_POLICY
using signal3 signal_with_thread_policymt_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_policymt_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_policymt_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_policymt_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_policymt_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_policymt_policy, A1, A2, A3, A4, A5, A6, A7, A8;} // namespace sigslot#endif /* RTC_BASE_THIRD_PARTY_SIGSLOT_SIGSLOT_H_ *///实现文件sigslot.cc
//
// sigslot.h: Signal/Slot classes
//
// Written by Sarah Thompson (sarahtelergy.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.#include sigslot.hnamespace sigslot {#ifdef _SIGSLOT_HAS_POSIX_THREADSpthread_mutex_t* multi_threaded_global::get_mutex() {static pthread_mutex_t g_mutex PTHREAD_MUTEX_INITIALIZER;return g_mutex;
}#endif // _SIGSLOT_HAS_POSIX_THREADS} // namespace sigslot
