From 0ef362472c2d9b6c037b3c3c52d69187436c46ef Mon Sep 17 00:00:00 2001
From: TerryE <terry@ellisons.org.uk>
Date: Sat, 20 Feb 2016 18:54:09 +0000
Subject: [PATCH] Add node.egc.setmode() + constants as per #609

---
 app/modules/node.c      | 25 +++++++++++++++++++++++++
 docs/en/modules/node.md | 21 +++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/app/modules/node.c b/app/modules/node.c
index 5b5e9e19..7be33737 100644
--- a/app/modules/node.c
+++ b/app/modules/node.c
@@ -9,6 +9,7 @@
 #include "lmem.h"
 #include "lobject.h"
 #include "lstate.h"
+#include "legc.h"
 
 #include "lopcodes.h"
 #include "lstring.h"
@@ -553,7 +554,30 @@ static int node_stripdebug (lua_State *L) {
 }
 #endif
 
+// Lua: node.egc.setmode( mode, [param])
+// where the mode is one of the node.egc constants  NOT_ACTIVE , ON_ALLOC_FAILURE, 
+// ON_MEM_LIMIT, ALWAYS.  In the case of ON_MEM_LIMIT an integer parameter is reqired
+// See legc.h and lecg.c.
+static int node_egc_setmode(lua_State* L) {
+  unsigned mode  = luaL_checkinteger(L, 1);
+  unsigned limit = luaL_optinteger (L, 2, 0);
+  
+  luaL_argcheck(L, mode <= (EGC_ON_ALLOC_FAILURE | EGC_ON_MEM_LIMIT | EGC_ALWAYS), 1, "invalid mode");
+  luaL_argcheck(L, !(mode & EGC_ON_MEM_LIMIT) || limit>0, 1, "limit must be non-zero");
+  
+  legc_set_mode( L, mode, limit );
+  return 0;
+}
 // Module function map
+
+static const LUA_REG_TYPE node_egc_map[] = {
+  { LSTRKEY( "setmode" ),           LFUNCVAL( node_egc_setmode ) },  
+  { LSTRKEY( "NOT_ACTIVE" ),        LNUMVAL( EGC_NOT_ACTIVE ) },
+  { LSTRKEY( "ON_ALLOC_FAILURE" ),  LNUMVAL( EGC_ON_ALLOC_FAILURE ) },
+  { LSTRKEY( "ON_MEM_LIMIT" ),      LNUMVAL( EGC_ON_MEM_LIMIT ) },
+  { LSTRKEY( "ALWAYS" ),            LNUMVAL( EGC_ALWAYS ) },
+  { LNILKEY, LNILVAL }
+};
 static const LUA_REG_TYPE node_map[] =
 {
   { LSTRKEY( "restart" ), LFUNCVAL( node_restart ) },
@@ -580,6 +604,7 @@ static const LUA_REG_TYPE node_map[] =
 #ifdef LUA_OPTIMIZE_DEBUG
   { LSTRKEY( "stripdebug" ), LFUNCVAL( node_stripdebug ) },
 #endif
+  { LSTRKEY( "egc" ), LROVAL( node_egc_map ) },
 
 // Combined to dsleep(us, option)
 // { LSTRKEY( "dsleepsetoption" ), LFUNCVAL( node_deepsleep_setoption) },
diff --git a/docs/en/modules/node.md b/docs/en/modules/node.md
index 6a4ec31b..e69707b1 100644
--- a/docs/en/modules/node.md
+++ b/docs/en/modules/node.md
@@ -378,3 +378,24 @@ node.compile('bigstuff.lua')
 #### See also
 [`node.compile()`](#nodecompile)
 
+# node.egc module
+
+## node.egc.setmode()
+
+Sets the Emergency Garbage Collector mode. [The EGC whitepaper](http://www.eluaproject.net/doc/v0.9/en_elua_egc.html)
+provides more detailed information on the EGC.
+
+####Syntax
+`node.egc.setmode(mode, [param])`
+
+#### Parameters
+- `mode`
+	- `node.ecg.NOT_ACTIVE` EGC inactive, no collection cycle will be forced in low memory situations
+	- `node.ecg.ON_ALLOC_FAILURE` Try to allocate a new block of memory, and run the garbage collector if the allocation fails. If the allocation fails even after running the garbage collector, the allocator will return with error. 
+	- `node.ecg.ON_MEM_LIMIT` Tun the garbage collector when the memory used by the Lua script goes beyond an upper `limit`. If the upper limit can't be satisfied even after running the garbage collector, the allocator will return with error.
+	- `node.ecg.ALWAYS` Run the garbage collector before each memory allocation. If the allocation fails even after running the garbage collector, the allocator will return with error. This mode is very efficient with regards to memory savings, but it's also the slowest.
+- `level` in the case of `node.ecg.ON_MEM_LIMIT`, this specifies the memory limit.
+  
+#### Returns
+`nil`
+