table-len.patch

Make tables honor __len
Author: dubiousjim@gmail.com
Derived from: Lua 5.2 sources
Updated: 17 May 2012

This patch makes #tbl honor a __len metamethod on tbl, as in Lua 5.2.
It also provides a new global function, rawlen.


diff -urN lua-5.1.5.orig/src/lbaselib.c lua-5.1.5/src/lbaselib.c
--- lua-5.1.5.orig/src/lbaselib.c	2008-02-14 11:46:22.000000000 -0500
+++ lua-5.1.5/src/lbaselib.c	2012-05-17 12:12:02.256721839 -0400
@@ -158,6 +158,15 @@
 }
 
 
+static int luaB_rawlen (lua_State *L) {
+  int t = lua_type(L, 1);
+  luaL_argcheck(L, t == LUA_TTABLE || t == LUA_TSTRING, 1,
+                   "table or string expected");
+  lua_pushinteger(L, lua_objlen(L, 1));
+  return 1;
+}
+
+
 static int luaB_rawequal (lua_State *L) {
   luaL_checkany(L, 1);
   luaL_checkany(L, 2);
@@ -458,6 +467,7 @@
   {"next", luaB_next},
   {"pcall", luaB_pcall},
   {"print", luaB_print},
+  {"rawlen", luaB_rawlen},
   {"rawequal", luaB_rawequal},
   {"rawget", luaB_rawget},
   {"rawset", luaB_rawset},
diff -urN lua-5.1.5.orig/src/ltm.c lua-5.1.5/src/ltm.c
--- lua-5.1.5.orig/src/ltm.c	2007-12-27 08:02:25.000000000 -0500
+++ lua-5.1.5/src/ltm.c	2012-05-17 12:12:02.252794245 -0400
@@ -30,9 +30,9 @@
 void luaT_init (lua_State *L) {
   static const char *const luaT_eventname[] = {  /* ORDER TM */
     "__index", "__newindex",
-    "__gc", "__mode", "__eq",
+    "__gc", "__mode", "__len", "__eq",
     "__add", "__sub", "__mul", "__div", "__mod",
-    "__pow", "__unm", "__len", "__lt", "__le",
+    "__pow", "__unm", "__lt", "__le",
     "__concat", "__call"
   };
   int i;
diff -urN lua-5.1.5.orig/src/ltm.h lua-5.1.5/src/ltm.h
--- lua-5.1.5.orig/src/ltm.h	2007-12-27 08:02:25.000000000 -0500
+++ lua-5.1.5/src/ltm.h	2012-05-17 12:12:02.254718931 -0400
@@ -20,6 +20,7 @@
   TM_NEWINDEX,
   TM_GC,
   TM_MODE,
+  TM_LEN,
   TM_EQ,  /* last tag method with `fast' access */
   TM_ADD,
   TM_SUB,
@@ -28,7 +29,6 @@
   TM_MOD,
   TM_POW,
   TM_UNM,
-  TM_LEN,
   TM_LT,
   TM_LE,
   TM_CONCAT,
diff -urN lua-5.1.5.orig/src/lvm.c lua-5.1.5/src/lvm.c
--- lua-5.1.5.orig/src/lvm.c	2011-08-17 16:43:11.000000000 -0400
+++ lua-5.1.5/src/lvm.c	2012-05-17 12:12:02.254718931 -0400
@@ -515,16 +515,23 @@
         const TValue *rb = RB(i);
         switch (ttype(rb)) {
           case LUA_TTABLE: {
-            setnvalue(ra, cast_num(luaH_getn(hvalue(rb))));
+            Table *h = hvalue(rb);
+            /* const TValue *tm = luaT_gettmbyobj(L, rb, TM_LEN); */
+            const TValue *tm = fasttm(L, h->metatable, TM_LEN);
+            if (tm == NULL) /* || ttisnil(tm)) */ {
+                setnvalue(ra, cast_num(luaH_getn(h)));
+            } else {
+                Protect(callTMres(L, ra, tm, rb, luaO_nilobject));
+            }
             break;
           }
           case LUA_TSTRING: {
             setnvalue(ra, cast_num(tsvalue(rb)->len));
             break;
           }
           default: {  /* try metamethod */
             Protect(
               if (!call_binTM(L, rb, luaO_nilobject, ra, TM_LEN))
                 luaG_typeerror(L, rb, "get length of");
             )
           }