From daa492ce07b62bd07d6120e2fabc3f6f2b6e50c7 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 10 Mar 2015 22:52:38 +1100
Subject: [PATCH] signal: add return value combiners

---
 signal.hpp      |  62 +++++++++++++++++++++++---
 signal.ipp      | 113 +++++++++++++++++++++++++++++-------------------
 test/signal.cpp |  47 ++++++++++++++++++++
 3 files changed, 172 insertions(+), 50 deletions(-)

diff --git a/signal.hpp b/signal.hpp
index 7dff0ba3..7c1c0fe4 100644
--- a/signal.hpp
+++ b/signal.hpp
@@ -21,16 +21,62 @@
 #define __UTIL_SIGNAL_HPP
 
 #include "nocopy.hpp"
+#include "types/traits.hpp"
 
 #include <functional>
 #include <list>
 #include <type_traits>
 
 namespace util {
-    template <typename F>
+    namespace combine {
+        template <typename F>
+        struct logical_and {
+            using R = typename func_traits<F>::return_type;
+
+            template <typename T, typename ...Args>
+            R operator() (T first, T last, Args&&... args)
+            {
+                while (first != last)
+                    if (!(*first++)(std::forward<Args> (args)...))
+                        return false;
+
+                return true;
+            }
+        };
+
+        template <typename F>
+        struct logical_or {
+            using R = typename func_traits<F>::return_type;
+
+            template <typename T, typename ...Args>
+            R operator() (T first, T last, Args&&... args)
+            {
+                while (first != last)
+                    if ((*first++)(std::forward<Args> (args)...))
+                        return true;
+
+                return false;
+            }
+        };
+
+        template <typename F>
+        struct noop {
+            using R = void;
+
+            template <typename T, typename ...Args>
+            R operator() (T first, T last, Args&&... args)
+            {
+                while (first != last) {
+                    (*first++)(std::forward<Args> (args)...);
+                }
+            }
+        };
+    }
+
+    template <typename F, template <typename> class C = combine::noop>
     class signal {
         public:
-            using R = std::result_of<F>;
+            using R = typename C<F>::R;
             using callback = std::function<F>;
 
             struct cookie;
@@ -40,9 +86,10 @@ namespace util {
             ~signal ();
 
             /// Add a callback to list.
+            cookie connect (callback&&);
             cookie connect (const callback&);
 
-            void disconnect (const cookie&);
+            void disconnect (cookie&);
 
             /// Disconnect all callbacks
             void clear (void);
@@ -51,16 +98,19 @@ namespace util {
             unsigned int size (void) const;
             bool empty (void) const;
 
-            /// Execute all callbacks, ignoring the return parameters. Does
-            /// not combine results.
+            /// Execute all callbacks
             template <typename ...Args>
-            void operator () (Args&&... tail);
+            R
+            operator() (Args&&... tail);
 
         private:
             typedef std::list<callback> group;
             group m_children;
     };
 
+    ///////////////////////////////////////////////////////////////////////////
+    // wrap a value in a signal and trigger on assignment
+    //template <typename T, template <typename> class C>
     template <typename T>
     class value_signal : public signal<void(T)> {
     public:
diff --git a/signal.ipp b/signal.ipp
index be599c82..76afa5ee 100644
--- a/signal.ipp
+++ b/signal.ipp
@@ -27,9 +27,9 @@
 
 namespace util {
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
-    struct signal<F>::cookie : public nocopy {
-        cookie (typename group::iterator, signal<F> &parent);
+    template <typename F, template <typename> class C>
+    struct signal<F,C>::cookie : public nocopy {
+        cookie (typename group::iterator, signal<F,C> &parent);
         cookie (cookie &&rhs);
         ~cookie ();
 
@@ -37,22 +37,22 @@ namespace util {
         void reset (void);
 
         typename group::iterator m_position;
-        signal<F> &m_parent;
+        signal<F,C> &m_parent;
     };
 
 
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
-    signal<F>::cookie::cookie (typename group::iterator _position,
-                               signal<F> &_parent):
+    template <typename F, template <typename> class C>
+    signal<F,C>::cookie::cookie (typename group::iterator _position,
+                                 signal<F,C> &_parent):
         m_position (_position),
         m_parent (_parent)
     { ; }
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
-    signal<F>::cookie::cookie (cookie &&rhs):
+    template <typename F, template <typename> class C>
+    signal<F,C>::cookie::cookie (cookie &&rhs):
         m_position (rhs.m_position),
         m_parent (rhs.m_parent)
     {
@@ -61,8 +61,8 @@ namespace util {
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
-    signal<F>::cookie::~cookie ()
+    template <typename F, template <typename> class C>
+    signal<F,C>::cookie::~cookie ()
     {
         if (m_parent.m_children.end () != m_position)
             m_parent.disconnect (*this);
@@ -70,59 +70,81 @@ namespace util {
 
 
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
+    template <typename F, template <typename> class C>
     void
-    signal<F>::cookie::reset (callback &&cb)
+    signal<F,C>::cookie::reset (callback &&cb)
     {
         *m_position = std::move (cb);
     }
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
+    template <typename F, template <typename> class C>
     void
-    signal<F>::cookie::reset (void)
+    signal<F,C>::cookie::reset (void)
     {
         m_position = m_parent.m_children.end ();
     }
 
 
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
-    signal<F>::signal ()
+    template <typename F, template <typename> class C>
+    signal<F,C>::signal ()
     { ; }
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
-    signal<F>::~signal ()
+    template <typename F, template <typename> class C>
+    signal<F,C>::~signal ()
     {
         CHECK (empty ());
     }
 
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
-    typename signal<F>::cookie
-    signal<F>::connect (const callback &_cb)
+    template <typename F, template <typename> class C>
+    typename signal<F,C>::cookie
+    signal<F,C>::connect (const callback &_cb)
     {
-        return cookie (m_children.insert (m_children.end (), _cb), *this);
+        return cookie (
+            m_children.insert (
+                m_children.end (),
+                std::move (_cb)
+            ),
+            *this
+        );
     }
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
+    template <typename F, template <typename> class C>
+    typename signal<F,C>::cookie
+    signal<F,C>::connect (callback &&_cb)
+    {
+        return cookie (
+            m_children.insert (
+                m_children.end (),
+                std::move (_cb)
+            ),
+            *this
+        );
+    }
+
+
+    //-------------------------------------------------------------------------
+    template <typename F, template <typename> class C>
     void
-    signal<F>::disconnect (const cookie &c)
+    signal<F,C>::disconnect (cookie &c)
     {
         m_children.erase (c.m_position);
+        c.m_position = m_children.end ();
     }
 
 
     //-------------------------------------------------------------------------
     /// Disconnect all callbacks
-    template <typename F>
+    template <typename F, template <typename> class C>
     void
-    signal<F>::clear (void) 
+    signal<F,C>::clear (void) 
     {
         m_children.clear ();
     }
@@ -130,42 +152,45 @@ namespace util {
 
     ///////////////////////////////////////////////////////////////////////////
     /// Returns the number of callbacks connected.
-    template <typename F>
+    template <typename F, template <typename> class C>
     unsigned int
-    signal<F>::size (void) const
+    signal<F,C>::size (void) const
     {
         return m_children.size ();
     }
 
 
     //-------------------------------------------------------------------------
-    template <typename F>
+    template <typename F, template <typename> class C>
     bool
-    signal<F>::empty (void) const
+    signal<F,C>::empty (void) const
     {
         return m_children.empty ();
     }
 
 
     ///////////////////////////////////////////////////////////////////////////
-    template <typename F>
+    template <typename F, template <typename> class C>
     template <typename ...Args>
-    void
-    signal<F>::operator () (Args&&... tail) {
+    typename signal<F,C>::R
+    signal<F,C>::operator () (Args&&... tail) {
         if (m_children.empty ())
-            return;
+            return R();
 
-        auto i = m_children.cbegin ();
-        bool looping;
+        //auto i = m_children.cbegin ();
+        //bool looping;
 
-        do {
-            // Increment before we execute so that the caller is able to
-            // deregister during execution.
-            auto current = i++;
-            looping = m_children.cend () != i;
+        C<F> combiner;
+        return combiner (m_children.begin (), m_children.end (), std::forward<Args> (tail)...);
 
-            (*current)(std::forward<Args> (tail)...);
-        } while (looping);
+        //do {
+        //    // Increment before we execute so that the caller is able to
+        //    // deregister themselves during execution.
+        //    auto current = i++;
+        //    looping = m_children.cend () != i;
+
+        //    (*current)(std::forward<Args> (tail)...);
+        //} while (looping);
     }
 
 
diff --git a/test/signal.cpp b/test/signal.cpp
index a4848dc2..260af61f 100644
--- a/test/signal.cpp
+++ b/test/signal.cpp
@@ -73,6 +73,51 @@ test_value_signal (void)
 }
 
 
+///////////////////////////////////////////////////////////////////////////////
+void
+test_combiner (void)
+{
+    {
+        util::signal<bool(void), util::combine::logical_and> sig;
+
+        unsigned count = 0;
+        auto raii = sig.connect ([&] (void) { ++count; return true; });
+        auto raii = sig.connect ([&] (void) { ++count; return true; });
+        auto raii = sig.connect ([&] (void) { ++count; return true; });
+
+        CHECK (sig ());
+        CHECK_EQ (count, 3);
+    }
+
+    {
+        util::signal<bool(void), util::combine::logical_and> sig;
+
+        unsigned count = 0;
+        auto raii = sig.connect ([&] (void) { ++count; return true; });
+        auto raii = sig.connect ([&] (void) { ++count; return false; });
+        auto raii = sig.connect ([&] (void) { ++count; return true; });
+
+        CHECK (!sig ());
+        CHECK_EQ (count, 2);
+    }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+void
+test_disconnect (void)
+{
+    util::signal<void(void)> sig;
+
+    util::signal<void(void)>::cookie a = sig.connect ([&] (void) { sig.disconnect (a); });
+    util::signal<void(void)>::cookie b = sig.connect ([&] (void) { sig.disconnect (b); });
+    util::signal<void(void)>::cookie c = sig.connect ([&] (void) { sig.disconnect (c); });
+    util::signal<void(void)>::cookie d = sig.connect ([&] (void) { sig.disconnect (d); });
+
+    sig ();
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 int
 main (int, char **)
@@ -81,6 +126,8 @@ main (int, char **)
     test_single ();
     test_double ();
     test_value_signal ();
+    test_combiner ();
+    test_disconnect ();
 
     return EXIT_SUCCESS;
 }