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685 lines
25 KiB
C++
685 lines
25 KiB
C++
#ifndef IG_NOD_INCLUDE_NOD_HPP
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#define IG_NOD_INCLUDE_NOD_HPP
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#include <vector> // std::vector
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#include <functional> // std::function
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#include <mutex> // std::mutex, std::lock_guard
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#include <memory> // std::shared_ptr, std::weak_ptr
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#include <algorithm> // std::find_if()
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#include <cassert> // assert()
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#include <thread> // std::this_thread::yield()
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#include <type_traits> // std::is_same
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#include <iterator> // std::back_inserter
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namespace nod {
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// implementational details
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namespace detail {
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/// Interface for type erasure when disconnecting slots
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struct disconnector {
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virtual void operator()( std::size_t index ) const = 0;
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};
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/// Deleter that doesn't delete
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inline void no_delete(disconnector*){
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};
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} // namespace detail
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/// Base template for the signal class
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template <class P, class T>
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class signal_type;
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/// Connection class.
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///
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/// This is used to be able to disconnect slots after they have been connected.
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/// Used as return type for the connect method of the signals.
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///
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/// Connections are default constructible.
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/// Connections are not copy constructible or copy assignable.
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/// Connections are move constructible and move assignable.
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///
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class connection {
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public:
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/// Default constructor
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connection() :
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_index()
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{}
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// Connection are not copy constructible or copy assignable
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connection( connection const& ) = delete;
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connection& operator=( connection const& ) = delete;
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/// Move constructor
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/// @param other The instance to move from.
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connection( connection&& other ) :
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_weak_disconnector( std::move(other._weak_disconnector) ),
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_index( other._index )
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{}
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/// Move assign operator.
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/// @param other The instance to move from.
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connection& operator=( connection&& other ) {
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_weak_disconnector = std::move( other._weak_disconnector );
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_index = other._index;
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return *this;
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}
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/// @returns `true` if the connection is connected to a signal object,
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/// and `false` otherwise.
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bool connected() const {
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return !_weak_disconnector.expired();
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}
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/// Disconnect the slot from the connection.
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///
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/// If the connection represents a slot that is connected to a signal object, calling
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/// this method will disconnect the slot from that object. The result of this operation
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/// is that the slot will stop receiving calls when the signal is invoked.
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void disconnect();
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private:
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/// The signal template is a friend of the connection, since it is the
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/// only one allowed to create instances using the meaningful constructor.
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template<class P,class T> friend class signal_type;
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/// Create a connection.
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/// @param shared_disconnector Disconnector instance that will be used to disconnect
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/// the connection when the time comes. A weak pointer
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/// to the disconnector will be held within the connection
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/// object.
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/// @param index The slot index of the connection.
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connection( std::shared_ptr<detail::disconnector> const& shared_disconnector, std::size_t index ) :
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_weak_disconnector( shared_disconnector ),
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_index( index )
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{}
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/// Weak pointer to the current disconnector functor.
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std::weak_ptr<detail::disconnector> _weak_disconnector;
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/// Slot index of the connected slot.
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std::size_t _index;
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};
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/// Scoped connection class.
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///
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/// This type of connection is automatically disconnected when
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/// the connection object is destructed.
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///
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class scoped_connection
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{
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public:
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/// Scoped are default constructible
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scoped_connection() = default;
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/// Scoped connections are not copy constructible
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scoped_connection( scoped_connection const& ) = delete;
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/// Scoped connections are not copy assingable
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scoped_connection& operator=( scoped_connection const& ) = delete;
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/// Move constructor
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scoped_connection( scoped_connection&& other ) :
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_connection( std::move(other._connection) )
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{}
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/// Move assign operator.
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/// @param other The instance to move from.
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scoped_connection& operator=( scoped_connection&& other ) {
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reset( std::move( other._connection ) );
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return *this;
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}
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/// Construct a scoped connection from a connection object
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/// @param connection The connection object to manage
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scoped_connection( connection&& c ) :
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_connection( std::forward<connection>(c) )
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{}
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/// destructor
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~scoped_connection() {
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disconnect();
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}
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/// Assignment operator moving a new connection into the instance.
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/// @note If the scoped_connection instance already contains a
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/// connection, that connection will be disconnected as if
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/// the scoped_connection was destroyed.
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/// @param c New connection to manage
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scoped_connection& operator=( connection&& c ) {
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reset( std::forward<connection>(c) );
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return *this;
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}
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/// Reset the underlying connection to another connection.
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/// @note The connection currently managed by the scoped_connection
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/// instance will be disconnected when resetting.
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/// @param c New connection to manage
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void reset( connection&& c = {} ) {
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disconnect();
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_connection = std::move(c);
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}
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/// Release the underlying connection, without disconnecting it.
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/// @returns The newly released connection instance is returned.
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connection release() {
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connection c = std::move(_connection);
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_connection = connection{};
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return c;
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}
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///
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/// @returns `true` if the connection is connected to a signal object,
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/// and `false` otherwise.
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bool connected() const {
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return _connection.connected();
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}
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/// Disconnect the slot from the connection.
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///
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/// If the connection represents a slot that is connected to a signal object, calling
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/// this method will disconnect the slot from that object. The result of this operation
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/// is that the slot will stop receiving calls when the signal is invoked.
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void disconnect() {
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_connection.disconnect();
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}
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private:
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/// Underlying connection object
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connection _connection;
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};
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/// Policy for multi threaded use of signals.
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///
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/// This policy provides mutex and lock types for use in
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/// a multithreaded environment, where signals and slots
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/// may exists in different threads.
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///
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/// This policy is used in the `nod::signal` type provided
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/// by the library.
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struct multithread_policy
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{
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using mutex_type = std::mutex;
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using mutex_lock_type = std::unique_lock<mutex_type>;
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/// Function that yields the current thread, allowing
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/// the OS to reschedule.
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static void yield_thread() {
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std::this_thread::yield();
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}
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/// Function that defers a lock to a lock function that prevents deadlock
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static mutex_lock_type defer_lock(mutex_type & m){
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return mutex_lock_type{m, std::defer_lock};
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}
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/// Function that locks two mutexes and prevents deadlock
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static void lock(mutex_lock_type & a,mutex_lock_type & b) {
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std::lock(a,b);
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}
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};
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/// Policy for single threaded use of signals.
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///
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/// This policy provides dummy implementations for mutex
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/// and lock types, resulting in that no synchronization
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/// will take place.
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///
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/// This policy is used in the `nod::unsafe_signal` type
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/// provided by the library.
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struct singlethread_policy
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{
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/// Dummy mutex type that doesn't do anything
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struct mutex_type{};
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/// Dummy lock type, that doesn't do any locking.
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struct mutex_lock_type
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{
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/// A lock type must be constructible from a
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/// mutex type from the same thread policy.
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explicit mutex_lock_type( mutex_type const& ) {
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}
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};
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/// Dummy implementation of thread yielding, that
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/// doesn't do any actual yielding.
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static void yield_thread() {
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}
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/// Dummy implemention of defer_lock that doesn't
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/// do anything
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static mutex_lock_type defer_lock(mutex_type &m){
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return mutex_lock_type{m};
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}
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/// Dummy implemention of lock that doesn't
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/// do anything
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static void lock(mutex_lock_type &,mutex_lock_type &) {
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}
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};
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/// Signal accumulator class template.
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///
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/// This acts sort of as a proxy for triggering a signal and
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/// accumulating the slot return values.
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///
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/// This class is not really intended to instantiate by client code.
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/// Instances are aquired as return values of the method `accumulate()`
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/// called on signals.
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///
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/// @tparam S Type of signal. The signal_accumulator acts
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/// as a type of proxy for a signal instance of
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/// this type.
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/// @tparam T Type of initial value of the accumulate algorithm.
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/// This type must meet the requirements of `CopyAssignable`
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/// and `CopyConstructible`
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/// @tparam F Type of accumulation function.
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/// @tparam A... Argument types of the underlying signal type.
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///
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template <class S, class T, class F, class...A>
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class signal_accumulator
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{
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public:
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/// Result type when calling the accumulating function operator.
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#if __cplusplus >= 201703L
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using result_type = typename std::invoke_result<F, T, typename S::slot_type::result_type>::type;
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#else
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using result_type = typename std::result_of<F(T, typename S::slot_type::result_type)>::type;
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#endif
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/// Construct a signal_accumulator as a proxy to a given signal
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//
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/// @param signal Signal instance.
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/// @param init Initial value of the accumulate algorithm.
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/// @param func Binary operation function object that will be
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/// applied to all slot return values.
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/// The signature of the function should be
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/// equivalent of the following:
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/// `R func( T1 const& a, T2 const& b )`
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/// - The signature does not need to have `const&`.
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/// - The initial value, type `T`, must be implicitly
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/// convertible to `R`
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/// - The return type `R` must be implicitly convertible
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/// to type `T1`.
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/// - The type `R` must be `CopyAssignable`.
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/// - The type `S::slot_type::result_type` (return type of
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/// the signals slots) must be implicitly convertible to
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/// type `T2`.
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signal_accumulator( S const& signal, T init, F func ) :
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_signal( signal ),
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_init( init ),
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_func( func )
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{}
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/// Function call operator.
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///
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/// Calling this will trigger the underlying signal and accumulate
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/// all of the connected slots return values with the current
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/// initial value and accumulator function.
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///
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/// When called, this will invoke the accumulator function will
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/// be called for each return value of the slots. The semantics
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/// are similar to the `std::accumulate` algorithm.
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///
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/// @param args Arguments to propagate to the slots of the
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/// underlying when triggering the signal.
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result_type operator()( A const& ... args ) const {
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return _signal.trigger_with_accumulator( _init, _func, args... );
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}
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private:
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/// Reference to the underlying signal to proxy.
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S const& _signal;
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/// Initial value of the accumulate algorithm.
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T _init;
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/// Accumulator function.
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F _func;
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};
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/// Signal template specialization.
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///
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/// This is the main signal implementation, and it is used to
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/// implement the observer pattern whithout the overhead
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/// boilerplate code that typically comes with it.
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///
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/// Any function or function object is considered a slot, and
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/// can be connected to a signal instance, as long as the signature
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/// of the slot matches the signature of the signal.
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///
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/// @tparam P Threading policy for the signal.
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/// A threading policy must provide two type definitions:
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/// - P::mutex_type, this type will be used as a mutex
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/// in the signal_type class template.
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/// - P::mutex_lock_type, this type must implement a
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/// constructor that takes a P::mutex_type as a parameter,
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/// and it must have the semantics of a scoped mutex lock
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/// like std::lock_guard, i.e. locking in the constructor
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/// and unlocking in the destructor.
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///
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/// @tparam R Return value type of the slots connected to the signal.
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/// @tparam A... Argument types of the slots connected to the signal.
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template <class P, class R, class... A >
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class signal_type<P,R(A...)>
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{
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public:
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/// signals are not copy constructible
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signal_type( signal_type const& ) = delete;
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/// signals are not copy assignable
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signal_type& operator=( signal_type const& ) = delete;
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/// signals are move constructible
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signal_type(signal_type&& other)
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{
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mutex_lock_type lock{other._mutex};
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_slot_count = std::move(other._slot_count);
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_slots = std::move(other._slots);
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if(other._shared_disconnector != nullptr)
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{
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_disconnector = disconnector{ this };
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_shared_disconnector = std::move(other._shared_disconnector);
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// replace the disconnector with our own disconnector
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*static_cast<disconnector*>(_shared_disconnector.get()) = _disconnector;
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}
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}
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/// signals are move assignable
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signal_type& operator=(signal_type&& other)
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{
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auto lock = thread_policy::defer_lock(_mutex);
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auto other_lock = thread_policy::defer_lock(other._mutex);
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thread_policy::lock(lock,other_lock);
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_slot_count = std::move(other._slot_count);
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_slots = std::move(other._slots);
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if(other._shared_disconnector != nullptr)
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{
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_disconnector = disconnector{ this };
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_shared_disconnector = std::move(other._shared_disconnector);
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// replace the disconnector with our own disconnector
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*static_cast<disconnector*>(_shared_disconnector.get()) = _disconnector;
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}
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return *this;
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}
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/// signals are default constructible
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signal_type() :
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_slot_count(0)
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{}
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// Destruct the signal object.
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~signal_type() {
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invalidate_disconnector();
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}
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/// Type that will be used to store the slots for this signal type.
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using slot_type = std::function<R(A...)>;
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/// Type that is used for counting the slots connected to this signal.
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using size_type = typename std::vector<slot_type>::size_type;
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/// Connect a new slot to the signal.
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///
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/// The connected slot will be called every time the signal
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/// is triggered.
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/// @param slot The slot to connect. This must be a callable with
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/// the same signature as the signal itself.
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/// @return A connection object is returned, and can be used to
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/// disconnect the slot.
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template <class T>
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connection connect( T&& slot ) {
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mutex_lock_type lock{ _mutex };
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_slots.push_back( std::forward<T>(slot) );
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std::size_t index = _slots.size()-1;
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if( _shared_disconnector == nullptr ) {
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_disconnector = disconnector{ this };
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_shared_disconnector = std::shared_ptr<detail::disconnector>{&_disconnector, detail::no_delete};
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}
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++_slot_count;
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return connection{ _shared_disconnector, index };
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}
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/// Function call operator.
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///
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/// Calling this is how the signal is triggered and the
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/// connected slots are called.
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///
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/// @note The slots will be called in the order they were
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/// connected to the signal.
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///
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/// @param args Arguments that will be propagated to the
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/// connected slots when they are called.
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void operator()( A const&... args ) const {
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for( auto const& slot : copy_slots() ) {
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if( slot ) {
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slot( args... );
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}
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}
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}
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/// Construct a accumulator proxy object for the signal.
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///
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/// The intended purpose of this function is to create a function
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/// object that can be used to trigger the signal and accumulate
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/// all the slot return values.
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///
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/// The algorithm used to accumulate slot return values is similar
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/// to `std::accumulate`. A given binary function is called for
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/// each return value with the parameters consisting of the
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/// return value of the accumulator function applied to the
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/// previous slots return value, and the current slots return value.
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/// A initial value must be provided for the first slot return type.
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///
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/// @note This can only be used on signals that have slots with
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/// non-void return types, since we can't accumulate void
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/// values.
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///
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/// @tparam T The type of the initial value given to the accumulator.
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/// @tparam F The accumulator function type.
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/// @param init Initial value given to the accumulator.
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/// @param op Binary operator function object to apply by the accumulator.
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/// The signature of the function should be
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/// equivalent of the following:
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/// `R func( T1 const& a, T2 const& b )`
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/// - The signature does not need to have `const&`.
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/// - The initial value, type `T`, must be implicitly
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/// convertible to `R`
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/// - The return type `R` must be implicitly convertible
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/// to type `T1`.
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/// - The type `R` must be `CopyAssignable`.
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/// - The type `S::slot_type::result_type` (return type of
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/// the signals slots) must be implicitly convertible to
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/// type `T2`.
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template <class T, class F>
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signal_accumulator<signal_type, T, F, A...> accumulate( T init, F op ) const {
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static_assert( std::is_same<R,void>::value == false, "Unable to accumulate slot return values with 'void' as return type." );
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return { *this, init, op };
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}
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/// Trigger the signal, calling the slots and aggregate all
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/// the slot return values into a container.
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///
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/// @tparam C The type of container. This type must be
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/// `DefaultConstructible`, and usable with
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/// `std::back_insert_iterator`. Additionally it
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/// must be either copyable or moveable.
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/// @param args The arguments to propagate to the slots.
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template <class C>
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C aggregate( A const&... args ) const {
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static_assert( std::is_same<R,void>::value == false, "Unable to aggregate slot return values with 'void' as return type." );
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C container;
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auto iterator = std::back_inserter( container );
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for( auto const& slot : copy_slots() ) {
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if( slot ) {
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(*iterator) = slot( args... );
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}
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}
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return container;
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}
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/// Count the number of slots connected to this signal
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/// @returns The number of connected slots
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size_type slot_count() const {
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return _slot_count;
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}
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/// Determine if the signal is empty, i.e. no slots are connected
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/// to it.
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/// @returns `true` is returned if the signal has no connected
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/// slots, and `false` otherwise.
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bool empty() const {
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return slot_count() == 0;
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}
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/// Disconnects all slots
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/// @note This operation invalidates all scoped_connection objects
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void disconnect_all_slots() {
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mutex_lock_type lock{ _mutex };
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_slots.clear();
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_slot_count = 0;
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invalidate_disconnector();
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}
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private:
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template<class, class, class, class...> friend class signal_accumulator;
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/// Thread policy currently in use
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using thread_policy = P;
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/// Type of mutex, provided by threading policy
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using mutex_type = typename thread_policy::mutex_type;
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/// Type of mutex lock, provided by threading policy
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using mutex_lock_type = typename thread_policy::mutex_lock_type;
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|
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/// Invalidate the internal disconnector object in a way
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/// that is safe according to the current thread policy.
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///
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/// This will effectively make all current connection objects to
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/// to this signal incapable of disconnecting, since they keep a
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/// weak pointer to the shared disconnector object.
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void invalidate_disconnector() {
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// If we are unlucky, some of the connected slots
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// might be in the process of disconnecting from other threads.
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// If this happens, we are risking to destruct the disconnector
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// object managed by our shared pointer before they are done
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// disconnecting. This would be bad. To solve this problem, we
|
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// discard the shared pointer (that is pointing to the disconnector
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|
// object within our own instance), but keep a weak pointer to that
|
|
// instance. We then stall the destruction until all other weak
|
|
// pointers have released their "lock" (indicated by the fact that
|
|
// we will get a nullptr when locking our weak pointer).
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std::weak_ptr<detail::disconnector> weak{_shared_disconnector};
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_shared_disconnector.reset();
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|
while( weak.lock() != nullptr ) {
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// we just yield here, allowing the OS to reschedule. We do
|
|
// this until all threads has released the disconnector object.
|
|
thread_policy::yield_thread();
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|
}
|
|
}
|
|
|
|
/// Retrieve a copy of the current slots
|
|
///
|
|
/// It's useful and necessary to copy the slots so we don't need
|
|
/// to hold the lock while calling the slots. If we hold the lock
|
|
/// we prevent the called slots from modifying the slots vector.
|
|
/// This simple "double buffering" will allow slots to disconnect
|
|
/// themself or other slots and connect new slots.
|
|
std::vector<slot_type> copy_slots() const
|
|
{
|
|
mutex_lock_type lock{ _mutex };
|
|
return _slots;
|
|
}
|
|
|
|
/// Implementation of the signal accumulator function call
|
|
template <class T, class F>
|
|
typename signal_accumulator<signal_type, T, F, A...>::result_type trigger_with_accumulator( T value, F& func, A const&... args ) const {
|
|
for( auto const& slot : copy_slots() ) {
|
|
if( slot ) {
|
|
value = func( value, slot( args... ) );
|
|
}
|
|
}
|
|
return value;
|
|
}
|
|
|
|
/// Implementation of the disconnection operation.
|
|
///
|
|
/// This is private, and only called by the connection
|
|
/// objects created when connecting slots to this signal.
|
|
/// @param index The slot index of the slot that should
|
|
/// be disconnected.
|
|
void disconnect( std::size_t index ) {
|
|
mutex_lock_type lock( _mutex );
|
|
assert( _slots.size() > index );
|
|
if( _slots[ index ] != nullptr ) {
|
|
--_slot_count;
|
|
}
|
|
_slots[ index ] = slot_type{};
|
|
while( _slots.size()>0 && !_slots.back() ) {
|
|
_slots.pop_back();
|
|
}
|
|
}
|
|
|
|
/// Implementation of the shared disconnection state
|
|
/// used by all connection created by signal instances.
|
|
///
|
|
/// This inherits the @ref detail::disconnector interface
|
|
/// for type erasure.
|
|
struct disconnector :
|
|
detail::disconnector
|
|
{
|
|
/// Default constructor, resulting in a no-op disconnector.
|
|
disconnector() :
|
|
_ptr(nullptr)
|
|
{}
|
|
|
|
/// Create a disconnector that works with a given signal instance.
|
|
/// @param ptr Pointer to the signal instance that the disconnector
|
|
/// should work with.
|
|
disconnector( signal_type<P,R(A...)>* ptr ) :
|
|
_ptr( ptr )
|
|
{}
|
|
|
|
/// Disconnect a given slot on the current signal instance.
|
|
/// @note If the instance is default constructed, or created
|
|
/// with `nullptr` as signal pointer this operation will
|
|
/// effectively be a no-op.
|
|
/// @param index The index of the slot to disconnect.
|
|
void operator()( std::size_t index ) const override {
|
|
if( _ptr ) {
|
|
_ptr->disconnect( index );
|
|
}
|
|
}
|
|
|
|
/// Pointer to the current signal.
|
|
signal_type<P,R(A...)>* _ptr;
|
|
};
|
|
|
|
/// Mutex to synchronize access to the slot vector
|
|
mutable mutex_type _mutex;
|
|
/// Vector of all connected slots
|
|
std::vector<slot_type> _slots;
|
|
/// Number of connected slots
|
|
size_type _slot_count;
|
|
/// Disconnector operation, used for executing disconnection in a
|
|
/// type erased manner.
|
|
disconnector _disconnector;
|
|
/// Shared pointer to the disconnector. All connection objects has a
|
|
/// weak pointer to this pointer for performing disconnections.
|
|
std::shared_ptr<detail::disconnector> _shared_disconnector;
|
|
};
|
|
|
|
// Implementation of the disconnect operation of the connection class
|
|
inline void connection::disconnect() {
|
|
auto ptr = _weak_disconnector.lock();
|
|
if( ptr ) {
|
|
(*ptr)( _index );
|
|
}
|
|
_weak_disconnector.reset();
|
|
}
|
|
|
|
/// Signal type that is safe to use in multithreaded environments,
|
|
/// where the signal and slots exists in different threads.
|
|
/// The multithreaded policy provides mutexes and locks to synchronize
|
|
/// access to the signals internals.
|
|
///
|
|
/// This is the recommended signal type, even for single threaded
|
|
/// environments.
|
|
template <class T> using signal = signal_type<multithread_policy, T>;
|
|
|
|
/// Signal type that is unsafe in multithreaded environments.
|
|
/// No synchronizations are provided to the signal_type for accessing
|
|
/// the internals.
|
|
///
|
|
/// Only use this signal type if you are sure that your environment is
|
|
/// single threaded and performance is of importance.
|
|
template <class T> using unsafe_signal = signal_type<singlethread_policy, T>;
|
|
} // namespace nod
|
|
|
|
#endif // IG_NOD_INCLUDE_NOD_HPP
|