Implement GC methods

* The GC methods are attached to a Rufus::Lua::State
  object.
* Implemented
** stopping and resuming GC
** Get the count in KB in use by Lua
** Manual GC

TODO.txt

@@ -12,8 +12,9 @@
 [o] fib.lua, use local, bench ! (2 times faster almost)
 
 [ ] add GC control methods (Alain)
-[ ] Add method to disable GC
-[ ] Add method to enable GC
+[X] Add method to disable GC
+[X] Add method to enable GC
 [ ] Look at parameters in Lua GC that can be tweaked
 [ ] Add method to tune GC parameters
+[ ] Test whether GC is truly independent for each state
 

lib/rufus/lua/lib.rb

@@ -91,6 +91,8 @@ module Lib
     attach_function :luaL_loadbuffer, [ :pointer, :string, :int, :string ], :int
     attach_function :luaL_ref, [ :pointer, :int ], :int
     attach_function :luaL_unref, [ :pointer, :int, :int ], :void
+
+    attach_function :lua_gc, [ :pointer, :int, :int ], :int
   end
 end
 end

lib/rufus/lua/state.rb

@@ -46,6 +46,16 @@ module StateMixin
     LUA_NOREF = -2
     LUA_REFNIL = -1
 
+    # Lua GC constants
+    LUA_GCSTOP = 0
+    LUA_GCRESTART = 1
+    LUA_GCCOLLECT = 2
+    LUA_GCCOUNT = 3
+    LUA_GCCOUNTB = 4
+    LUA_GCSTEP = 5
+    LUA_GCSETPAUSE = 6
+    LUA_GCSETSTEPMUL = 7
+
     TNONE = -1
     TNIL = 0
     TBOOLEAN = 1
@@ -361,6 +371,43 @@ def [] (k)
     def close
 
       Lib.lua_close(@pointer)
+      @pointer = nil
+    end
+
+    #
+    # Returns current amount of memory in KB in use by Lua
+    #
+    def gc_count
+
+      raise "closed" unless @pointer
+      Lib.lua_gc(@pointer, LUA_GCCOUNT, 0)
+    end
+
+    #
+    # Runs garbage collection
+    #
+    def gc_collect!
+
+      raise "closed" unless @pointer
+      Lib.lua_gc(@pointer, LUA_GCCOLLECT, 0)
+    end
+
+    #
+    # Stop garbage collection for this state
+    #
+    def gc_stop
+
+      raise "closed" unless @pointer
+      Lib.lua_gc(@pointer, LUA_GCSTOP, 0)
+    end
+
+    #
+    # Restart garbage collection for this state
+    #
+    def gc_resume
+
+      raise "closed" unless @pointer
+      Lib.lua_gc(@pointer, LUA_GCRESTART, 0)
     end
   end
 end

test/gc0.rb

@@ -0,0 +1,19 @@
+#
+# Test garbage collection API from rufus-lua
+#
+
+$:.unshift('lib')
+
+require 'rubygems'
+require 'rufus/lua'
+
+
+puts "Creating a new state..."
+s = Rufus::Lua::State.new
+puts "  #{s.gc_count} KB in use by Lua interpreter"
+puts "  Calling into Lua..."
+puts s.eval("return table.concat({ '    hello', 'from', 'Lua' }, ' ')")
+puts "  #{s.gc_count} KB in use by Lua interpreter"
+puts "Performing forced garbage collection..."
+s.gc_collect!
+puts "  #{s.gc_count} KB in use by Lua interpreter"