From 204c8016c70ea0e91534e30bc5b879da5540e1de Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Thu, 14 Apr 2016 03:08:02 +0200
Subject: [PATCH] allow to compare C class instances from lua

---
 libs/ardour/luabindings.cc             |  3 +++
 libs/lua/LuaBridge/detail/CFunctions.h | 13 +++++++++++++
 libs/lua/LuaBridge/detail/Namespace.h  | 15 +++++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/libs/ardour/luabindings.cc b/libs/ardour/luabindings.cc
index 5dcd0964cd..2fa6fa0604 100644
--- a/libs/ardour/luabindings.cc
+++ b/libs/ardour/luabindings.cc
@@ -1005,6 +1005,7 @@ LuaBindings::dsp (lua_State* L)
 		.beginNamespace ("ARDOUR")
 
 		.beginClass <AudioBuffer> ("AudioBuffer")
+		.addEqualCheck ()
 		.addFunction ("data", (Sample*(AudioBuffer::*)(framecnt_t))&AudioBuffer::data)
 		.addFunction ("silence", &AudioBuffer::silence)
 		.addFunction ("apply_gain", &AudioBuffer::apply_gain)
@@ -1013,12 +1014,14 @@ LuaBindings::dsp (lua_State* L)
 		.endClass()
 
 		.beginClass <MidiBuffer> ("MidiBuffer")
+		.addEqualCheck ()
 		.addFunction ("silence", &MidiBuffer::silence)
 		.addFunction ("empty", &MidiBuffer::empty)
 		// TODO iterators..
 		.endClass()
 
 		.beginClass <BufferSet> ("BufferSet")
+		.addEqualCheck ()
 		.addFunction ("get_audio", static_cast<AudioBuffer&(BufferSet::*)(size_t)>(&BufferSet::get_audio))
 		.addFunction ("count", static_cast<const ChanCount&(BufferSet::*)()const>(&BufferSet::count))
 		.endClass()
diff --git a/libs/lua/LuaBridge/detail/CFunctions.h b/libs/lua/LuaBridge/detail/CFunctions.h
index 29b361b690..6f43919216 100644
--- a/libs/lua/LuaBridge/detail/CFunctions.h
+++ b/libs/lua/LuaBridge/detail/CFunctions.h
@@ -366,6 +366,19 @@ struct CFunc
     }
   };
 
+  template <class T>
+  struct ClassEqualCheck
+  {
+    static int f (lua_State* L)
+    {
+      T const* const t0 = Userdata::get <T> (L, 1, true);
+      T const* const t1 = Userdata::get <T> (L, 2, true);
+      Stack <bool>::push (L, t0 == t1);
+      return 1;
+    }
+  };
+
+
   template <class T>
   struct PtrNullCheck
   {
diff --git a/libs/lua/LuaBridge/detail/Namespace.h b/libs/lua/LuaBridge/detail/Namespace.h
index 722d02e4a7..c859d8d151 100644
--- a/libs/lua/LuaBridge/detail/Namespace.h
+++ b/libs/lua/LuaBridge/detail/Namespace.h
@@ -1039,6 +1039,15 @@ private:
       return addConstructor <void (*) ()> ();
     }
 
+    Class <T>& addEqualCheck ()
+    {
+      PRINTDOC("Member Function", _name << "sameinstance", std::string("bool"), std::string("void (*)(" + type_name <T>() + ")"))
+      assert (lua_istable (L, -1));
+      lua_pushcclosure (L, &CFunc::ClassEqualCheck <T>::f, 0);
+      rawsetfield (L, -3, "sameinstance");
+      return *this;
+    }
+
   };
 
   /** C Array to/from table */
@@ -1060,6 +1069,8 @@ private:
           std::string(""), "int (*)(lua_State*)")
       PRINTDOC ("Ext C Function", _name << "set_table",
           std::string(""), "int (*)(lua_State*)")
+      PRINTDOC("Member Function", _name << "sameinstance",
+          std::string("bool"), std::string("void (*)(" + type_name <T>() + "*)"))
 
       m_stackSize = parent->m_stackSize + 3;
       parent->m_stackSize = 0;
@@ -1117,6 +1128,10 @@ private:
 
         lua_pushcclosure (L, &CFunc::setTable <T>, 0);
         rawsetfield (L, -3, "set_table"); // class table
+
+        lua_pushcclosure (L, &CFunc::ClassEqualCheck <T>::f, 0);
+        rawsetfield (L, -3, "sameinstance");
+
       }
       else
       {