From f543ff65fc6a5c44cc939555f92fcf2aaa0a7e50 Mon Sep 17 00:00:00 2001
From: Francois Perrad <francois.perrad@gadz.org>
Date: Sat, 6 May 2017 10:31:55 +0200
Subject: [PATCH] backport lua_len from 5.2

---
 src/lj_api.c | 19 +++++++++++++++++++
 src/lua.h    |  1 +
 2 files changed, 20 insertions(+)

diff --git a/src/lj_api.c b/src/lj_api.c
index 84508d7d..35698cc4 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -806,6 +806,25 @@ LUA_API void lua_concat(lua_State *L, int n)
   /* else n == 1: nothing to do. */
 }
 
+LUA_API void lua_len (lua_State *L, int idx)
+{
+  TValue *o = index2adr_stack(L, idx);
+  if (tvisstr(o)) {
+    setnumV(L->top, strV(o)->len);
+  } else if (tvistab(o) && (!LJ_52 || tvisnil(lj_meta_lookup(L, o, MM_len)))) {
+    setnumV(L->top, lj_tab_len(tabV(o)));
+  } else {
+    TValue *v;
+    L->top = lj_meta_len(L, o);
+    L->top += 2;
+    lj_vm_call(L, L->top-2, 1+1);
+    L->top -= 2+LJ_FR2;
+    v = L->top+1+LJ_FR2;
+    copyTV(L, L->top, v);
+  }
+  incr_top(L);
+}
+
 /* -- Object getters ------------------------------------------------------ */
 
 LUA_API void lua_gettable(lua_State *L, int idx)
diff --git a/src/lua.h b/src/lua.h
index 2a548c5a..e6b74d0f 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -353,6 +353,7 @@ LUA_API void lua_copy (lua_State *L, int fromidx, int toidx);
 LUA_API lua_Number lua_tonumberx (lua_State *L, int idx, int *isnum);
 LUA_API lua_Integer lua_tointegerx (lua_State *L, int idx, int *isnum);
 LUA_API size_t lua_rawlen (lua_State *L, int idx);
+LUA_API void lua_len (lua_State *L, int idx);
 
 /* From Lua 5.3. */
 LUA_API int lua_isyieldable (lua_State *L);