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commit 4b91e9cde630573cb35bb20101eb74cf5cf79a27
parent 26c5f56ad1ac6f0409e638f44af75da09f2b0a0b
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date:   Tue, 16 Sep 1997 16:25:38 -0300

Tag methods

Diffstat:

Dfallback.c | 353-------------------------------------------------------------------------------


Dfallback.h | 64----------------------------------------------------------------


Altm.c | 317+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


Altm.h | 61+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


4 files changed, 378 insertions(+), 417 deletions(-)

diff --git a/fallback.c b/fallback.c
@@ -1,353 +0,0 @@
-/*
-** fallback.c
-** TecCGraf - PUC-Rio
-*/
- 
-char *rcs_fallback="$Id: fallback.c,v 2.10 1997/07/03 22:06:06 roberto Exp $";
-
-#include <stdio.h>
-#include <string.h>
- 
-#include "auxlib.h"
-#include "luamem.h"
-#include "fallback.h"
-#include "opcode.h"
-#include "lua.h"
-#include "table.h"
-#include "tree.h"
-#include "hash.h"
-
-
-
-/* -------------------------------------------
-** Reference routines
-*/
-
-static struct ref {
-  TObject o;
-  enum {LOCK, HOLD, FREE, COLLECTED} status;
-} *refArray = NULL;
-static int refSize = 0;
-
-int luaI_ref (TObject *object, int lock)
-{
-  int i;
-  int oldSize;
-  if (ttype(object) == LUA_T_NIL)
-    return -1;   /* special ref for nil */
-  for (i=0; i<refSize; i++)
-    if (refArray[i].status == FREE)
-      goto found;
-  /* no more empty spaces */
-  oldSize = refSize;
-  refSize = growvector(&refArray, refSize, struct ref, refEM, MAX_WORD);
-  for (i=oldSize; i<refSize; i++)
-    refArray[i].status = FREE;
-  i = oldSize;
- found:
-  refArray[i].o = *object;
-  refArray[i].status = lock ? LOCK : HOLD;
-  return i;
-}
-
-
-void lua_unref (int ref)
-{
-  if (ref >= 0 && ref < refSize)
-    refArray[ref].status = FREE;
-}
-
-
-TObject *luaI_getref (int ref)
-{
-  static TObject nul = {LUA_T_NIL, {0}};
-  if (ref == -1)
-    return &nul;
-  if (ref >= 0 && ref < refSize &&
-      (refArray[ref].status == LOCK || refArray[ref].status == HOLD))
-    return &refArray[ref].o;
-  else
-    return NULL;
-}
-
-
-void luaI_travlock (int (*fn)(TObject *))
-{
-  int i;
-  for (i=0; i<refSize; i++)
-    if (refArray[i].status == LOCK)
-      fn(&refArray[i].o);
-}
-
-
-void luaI_invalidaterefs (void)
-{
-  int i;
-  for (i=0; i<refSize; i++)
-    if (refArray[i].status == HOLD && !luaI_ismarked(&refArray[i].o))
-      refArray[i].status = COLLECTED;
-}
-
-
-/* -------------------------------------------
-* Internal Methods 
-*/
-
-char *luaI_eventname[] = {  /* ORDER IM */
-  "gettable", "settable", "index", "getglobal", "setglobal", "add",
-  "sub", "mul", "div", "pow", "unm", "lt", "le", "gt", "ge",
-  "concat", "gc", "function",
-  NULL
-};
-
-
-
-static int luaI_checkevent (char *name, char *list[])
-{
-  int e = luaI_findstring(name, list);
-  if (e < 0)
-    luaL_verror("`%s' is not a valid event name", name);
-  return e;
-}
-
-
-struct IM *luaI_IMtable = NULL;
-
-static int IMtable_size = 0;
-static int last_tag = LUA_T_NIL;  /* ORDER LUA_T */
-
-
-/* events in LUA_T_LINE are all allowed, since this is used as a
-*  'placeholder' for "default" fallbacks
-*/
-static char validevents[NUM_TYPES][IM_N] = { /* ORDER LUA_T, ORDER IM */
-{1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1},  /* LUA_T_USERDATA */
-{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},  /* LUA_T_LINE */
-{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},  /* LUA_T_CMARK */
-{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},  /* LUA_T_MARK */
-{1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0},  /* LUA_T_CFUNCTION */
-{1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0},  /* LUA_T_FUNCTION */
-{0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},  /* LUA_T_ARRAY */
-{1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},  /* LUA_T_STRING */
-{1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1},  /* LUA_T_NUMBER */
-{1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}   /* LUA_T_NIL */
-};
-
-static int validevent (lua_Type t, int e)
-{ /* ORDER LUA_T */
-  return (t < LUA_T_NIL) ?  1 : validevents[-t][e];
-}
-
-
-static void init_entry (int tag)
-{
-  int i;
-  for (i=0; i<IM_N; i++)
-    ttype(luaI_getim(tag, i)) = LUA_T_NIL;
-}
-
-void luaI_initfallbacks (void)
-{
-  if (luaI_IMtable == NULL) {
-    int i;
-    IMtable_size = NUM_TYPES+10;
-    luaI_IMtable = newvector(IMtable_size, struct IM);
-    for (i=LUA_T_NIL; i<=LUA_T_USERDATA; i++)
-      init_entry(i);
-  }
-}
-
-int lua_newtag (void)
-{
-  --last_tag;
-  if ((-last_tag) >= IMtable_size) {
-    luaI_initfallbacks();
-    IMtable_size = growvector(&luaI_IMtable, IMtable_size,
-                              struct IM, memEM, MAX_INT);
-  }
-  init_entry(last_tag);
-  return last_tag;
-}
-
-
-static void checktag (int tag)
-{
-  if (!(last_tag <= tag && tag <= 0))
-    luaL_verror("%d is not a valid tag", tag);
-}
-
-void luaI_realtag (int tag)
-{
-  if (!(last_tag <= tag && tag < LUA_T_NIL))
-    luaL_verror("tag %d is not result of `newtag'", tag);
-}
-
-
-void luaI_settag (int tag, TObject *o)
-{
-  luaI_realtag(tag);
-  switch (ttype(o)) {
-    case LUA_T_ARRAY:
-      o->value.a->htag = tag;
-      break;
-    case LUA_T_USERDATA:
-      o->value.ts->tag = tag;
-      break;
-    default:
-      luaL_verror("cannot change the tag of a %s", luaI_typenames[-ttype(o)]);
-  }
-}
-
-
-int luaI_efectivetag (TObject *o)
-{
-  lua_Type t = ttype(o);
-  if (t == LUA_T_USERDATA) {
-    int tag = o->value.ts->tag;
-    return (tag >= 0) ? LUA_T_USERDATA : tag;
-  }
-  else if (t == LUA_T_ARRAY)
-    return o->value.a->htag;
-  else return t;
-}
-
-
-void luaI_gettagmethod (void)
-{
-  int t = (int)luaL_check_number(1);
-  int e = luaI_checkevent(luaL_check_string(2), luaI_eventname);
-  checktag(t);
-  if (validevent(t, e))
-    luaI_pushobject(luaI_getim(t,e));
-}
-
-
-void luaI_settagmethod (void)
-{
-  int t = (int)luaL_check_number(1);
-  int e = luaI_checkevent(luaL_check_string(2), luaI_eventname);
-  lua_Object func = lua_getparam(3);
-  checktag(t);
-  if (!validevent(t, e))
-    luaL_verror("cannot change internal method `%s' for tag %d",
-                luaI_eventname[e], t);
-  luaL_arg_check(lua_isnil(func) || lua_isfunction(func),
-                 3, "function expected");
-  luaI_pushobject(luaI_getim(t,e));
-  *luaI_getim(t, e) = *luaI_Address(func);
-}
-
-
-void luaI_seterrormethod (void)
-{
-  lua_Object func = lua_getparam(1);
-  luaL_arg_check(lua_isnil(func) || lua_isfunction(func),
-                 1, "function expected");
-  luaI_pushobject(&luaI_errorim);
-  luaI_errorim = *luaI_Address(func);
-}
-
-char *luaI_travfallbacks (int (*fn)(TObject *))
-{
-  int e;
-  if (fn(&luaI_errorim))
-    return "error";
-  for (e=IM_GETTABLE; e<=IM_FUNCTION; e++) {  /* ORDER IM */
-    int t;
-    for (t=0; t>=last_tag; t--)
-      if (fn(luaI_getim(t,e)))
-        return luaI_eventname[e];
-  }
-  return NULL;
-}
-
-
-/*
-* ===================================================================
-* compatibility with old fallback system
-*/
-#if	LUA_COMPAT2_5
-
-static void errorFB (void)
-{
-  lua_Object o = lua_getparam(1);
-  if (lua_isstring(o))
-    fprintf (stderr, "lua: %s\n", lua_getstring(o));
-  else
-    fprintf(stderr, "lua: unknown error\n");
-}
- 
-
-static void nilFB (void) { }
- 
-
-static void typeFB (void)
-{
-  lua_error("unexpected type");
-}
-
-
-static void fillvalids (IMS e, TObject *func)
-{
-  int t;
-  for (t=LUA_T_NIL; t<=LUA_T_USERDATA; t++)
-    if (validevent(t, e))
-      *luaI_getim(t, e) = *func;
-}
-
-
-void luaI_setfallback (void)
-{
-  static char *oldnames [] = {"error", "getglobal", "arith", "order", NULL};
-  TObject oldfunc;
-  lua_CFunction replace;
-  char *name = luaL_check_string(1);
-  lua_Object func = lua_getparam(2);
-  luaI_initfallbacks();
-  luaL_arg_check(lua_isfunction(func), 2, "function expected");
-  switch (luaI_findstring(name, oldnames)) {
-    case 0:  /* old error fallback */
-      oldfunc = luaI_errorim;
-      luaI_errorim = *luaI_Address(func);
-      replace = errorFB;
-      break;
-    case 1:  /* old getglobal fallback */
-      oldfunc = *luaI_getim(LUA_T_NIL, IM_GETGLOBAL);
-      *luaI_getim(LUA_T_NIL, IM_GETGLOBAL) = *luaI_Address(func);
-      replace = nilFB;
-      break;
-    case 2: {  /* old arith fallback */
-      int i;
-      oldfunc = *luaI_getim(LUA_T_NUMBER, IM_POW);
-      for (i=IM_ADD; i<=IM_UNM; i++)  /* ORDER IM */
-        fillvalids(i, luaI_Address(func));
-      replace = typeFB;
-      break;
-    }
-    case 3: {  /* old order fallback */
-      int i;
-      oldfunc = *luaI_getim(LUA_T_LINE, IM_LT);
-      for (i=IM_LT; i<=IM_GE; i++)  /* ORDER IM */
-        fillvalids(i, luaI_Address(func));
-      replace = typeFB;
-      break;
-    }
-    default: {
-      int e;
-      if ((e = luaI_findstring(name, luaI_eventname)) >= 0) {
-        oldfunc = *luaI_getim(LUA_T_LINE, e);
-        fillvalids(e, luaI_Address(func));
-        replace = (e == IM_GC || e == IM_INDEX) ? nilFB : typeFB;
-      }
-      else {
-        luaL_verror("`%s' is not a valid fallback name", name);
-        replace = NULL;  /* to avoid warnings */
-      }
-    }
-  }
-  if (oldfunc.ttype != LUA_T_NIL)
-    luaI_pushobject(&oldfunc);
-  else
-    lua_pushcfunction(replace);
-}
-#endif 
diff --git a/fallback.h b/fallback.h
@@ -1,64 +0,0 @@
-/*
-** $Id: fallback.h,v 1.24 1997/07/03 22:06:06 roberto Exp $
-*/
- 
-#ifndef fallback_h
-#define fallback_h
-
-#include "lua.h"
-#include "opcode.h"
-
-/*
-* WARNING: if you change the order of this enumeration,
-* grep "ORDER IM"
-*/
-typedef enum {
-  IM_GETTABLE = 0,
-  IM_SETTABLE,
-  IM_INDEX,
-  IM_GETGLOBAL,
-  IM_SETGLOBAL,
-  IM_ADD,
-  IM_SUB,
-  IM_MUL,
-  IM_DIV,
-  IM_POW,
-  IM_UNM,
-  IM_LT,
-  IM_LE,
-  IM_GT,
-  IM_GE,
-  IM_CONCAT,
-  IM_GC,
-  IM_FUNCTION
-} IMS;
-
-#define IM_N 18
-
-
-extern struct IM {
-  TObject int_method[IM_N];
-} *luaI_IMtable;
-
-extern char *luaI_eventname[];
-
-#define luaI_getim(tag,event) (&luaI_IMtable[-(tag)].int_method[event])
-#define luaI_getimbyObj(o,e)  (luaI_getim(luaI_efectivetag(o),(e)))
-
-void luaI_setfallback (void);
-int luaI_ref (TObject *object, int lock);
-TObject *luaI_getref (int ref);
-void luaI_travlock (int (*fn)(TObject *));
-void luaI_invalidaterefs (void);
-char *luaI_travfallbacks (int (*fn)(TObject *));
-
-void luaI_settag (int tag, TObject *o);
-void luaI_realtag (int tag);
-int luaI_efectivetag (TObject *o);
-void luaI_settagmethod (void);
-void luaI_gettagmethod (void);
-void luaI_seterrormethod (void);
-void luaI_initfallbacks (void);
-
-#endif
-
diff --git a/ltm.c b/ltm.c
@@ -0,0 +1,317 @@
+/*
+** $Id: $
+** Tag methods
+** See Copyright Notice in lua.h
+*/
+
+
+#include <stdio.h>
+#include <string.h>
+
+#include "lauxlib.h"
+#include "ldo.h"
+#include "lmem.h"
+#include "lobject.h"
+#include "ltm.h"
+
+static struct IM init_IM[NUM_TYPES] = {
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}},
+{{{LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}},
+  {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}, {LUA_T_NIL, {NULL}}}}
+};
+
+
+
+
+char *luaT_eventname[] = {  /* ORDER IM */
+  "gettable", "settable", "index", "getglobal", "setglobal", "add",
+  "sub", "mul", "div", "pow", "unm", "lt", "le", "gt", "ge",
+  "concat", "gc", "function",
+  NULL
+};
+
+
+static int luaI_checkevent (char *name, char *list[])
+{
+  int e = luaO_findstring(name, list);
+  if (e < 0)
+    luaL_verror("`%.50s' is not a valid event name", name);
+  return e;
+}
+
+
+struct IM *luaT_IMtable = init_IM;
+
+static int IMtable_size = NUM_TYPES;
+
+static int last_tag = -(NUM_TYPES-1);
+
+
+/* events in LUA_T_LINE are all allowed, since this is used as a
+*  'placeholder' for "default" fallbacks
+*/
+static char validevents[NUM_TYPES][IM_N] = { /* ORDER LUA_T, ORDER IM */
+{1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1},  /* LUA_T_USERDATA */
+{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},  /* LUA_T_LINE */
+{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},  /* LUA_T_CMARK */
+{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},  /* LUA_T_MARK */
+{1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0},  /* LUA_T_CFUNCTION */
+{1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0},  /* LUA_T_FUNCTION */
+{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},  /* LUA_T_PROTO */
+{0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},  /* LUA_T_ARRAY */
+{1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},  /* LUA_T_STRING */
+{1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1},  /* LUA_T_NUMBER */
+{1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}   /* LUA_T_NIL */
+};
+
+static int validevent (lua_Type t, int e)
+{ /* ORDER LUA_T */
+  return (t < LUA_T_NIL) ?  1 : validevents[-t][e];
+}
+
+
+static void init_entry (int tag)
+{
+  int i;
+  for (i=0; i<IM_N; i++)
+    ttype(luaT_getim(tag, i)) = LUA_T_NIL;
+}
+
+int lua_newtag (void)
+{
+  --last_tag;
+  if ((-last_tag) >= IMtable_size) {
+    if (luaT_IMtable == init_IM) {  /* fist time? */
+      IMtable_size *= 2;
+      luaT_IMtable = luaM_newvector(IMtable_size, struct IM);
+      memcpy(luaT_IMtable, init_IM, sizeof(init_IM));
+    }
+    else
+      IMtable_size = luaM_growvector(&luaT_IMtable, IMtable_size,
+                                struct IM, memEM, MAX_INT);
+  }
+  init_entry(last_tag);
+  return last_tag;
+}
+
+
+static void checktag (int tag)
+{ /* ORDER LUA_T */
+  if (!(last_tag <= tag && tag <= 0))
+    luaL_verror("%d is not a valid tag", tag);
+}
+
+void luaT_realtag (int tag)
+{
+  if (!(last_tag <= tag && tag < LUA_T_NIL))
+    luaL_verror("tag %d is not result of `newtag'", tag);
+}
+
+
+
+int luaT_efectivetag (TObject *o)
+{
+  lua_Type t = ttype(o);
+  if (t == LUA_T_USERDATA) {
+    int tag = o->value.ts->tag;
+    return (tag >= 0) ? LUA_T_USERDATA : tag;
+  }
+  else if (t == LUA_T_ARRAY)
+    return o->value.a->htag;
+  else return t;
+}
+
+
+TObject *luaT_gettagmethod (int t, char *event)
+{
+  int e = luaI_checkevent(event, luaT_eventname);
+  checktag(t);
+  if (validevent(t, e))
+    return luaT_getim(t,e);
+  else
+    return luaT_getim(LUA_T_CMARK, IM_GETTABLE);  /* always nil */
+}
+
+
+void luaT_settagmethod (int t, char *event, TObject *func)
+{
+  TObject temp = *func;
+  int e = luaI_checkevent(event, luaT_eventname);
+  checktag(t);
+  if (!validevent(t, e))
+    luaL_verror("settagmethod: cannot change internal method `%s' for tag %d",
+                luaT_eventname[e], t);
+  *func = *luaT_getim(t,e);
+  *luaT_getim(t, e) = temp;
+}
+
+
+char *luaT_travtagmethods (int (*fn)(TObject *))
+{
+  int e;
+  if (fn(&luaD_errorim))
+    return "error";
+  for (e=IM_GETTABLE; e<=IM_FUNCTION; e++) {  /* ORDER IM */
+    int t;
+    for (t=0; t>=last_tag; t--)
+      if (fn(luaT_getim(t,e)))
+        return luaT_eventname[e];
+  }
+  return NULL;
+}
+
+
+/*
+* ===================================================================
+* compatibility with old fallback system
+*/
+#if	LUA_COMPAT2_5
+
+#include "lapi.h"
+
+static void errorFB (void)
+{
+  lua_Object o = lua_getparam(1);
+  if (lua_isstring(o))
+    fprintf(stderr, "lua: %s\n", lua_getstring(o));
+  else
+    fprintf(stderr, "lua: unknown error\n");
+}
+
+
+static void nilFB (void) { }
+
+
+static void typeFB (void)
+{
+  lua_error("unexpected type");
+}
+
+
+static void fillvalids (IMS e, TObject *func)
+{
+  int t;
+  for (t=LUA_T_NIL; t<=LUA_T_USERDATA; t++)
+    if (validevent(t, e))
+      *luaT_getim(t, e) = *func;
+}
+
+
+void luaT_setfallback (void)
+{
+  static char *oldnames [] = {"error", "getglobal", "arith", "order", NULL};
+  TObject oldfunc;
+  lua_CFunction replace;
+  char *name = luaL_check_string(1);
+  lua_Object func = lua_getparam(2);
+  luaL_arg_check(lua_isfunction(func), 2, "function expected");
+  switch (luaO_findstring(name, oldnames)) {
+    case 0:  /* old error fallback */
+      oldfunc = luaD_errorim;
+      luaD_errorim = *luaA_Address(func);
+      replace = errorFB;
+      break;
+    case 1:  /* old getglobal fallback */
+      oldfunc = *luaT_getim(LUA_T_NIL, IM_GETGLOBAL);
+      *luaT_getim(LUA_T_NIL, IM_GETGLOBAL) = *luaA_Address(func);
+      replace = nilFB;
+      break;
+    case 2: {  /* old arith fallback */
+      int i;
+      oldfunc = *luaT_getim(LUA_T_NUMBER, IM_POW);
+      for (i=IM_ADD; i<=IM_UNM; i++)  /* ORDER IM */
+        fillvalids(i, luaA_Address(func));
+      replace = typeFB;
+      break;
+    }
+    case 3: {  /* old order fallback */
+      int i;
+      oldfunc = *luaT_getim(LUA_T_LINE, IM_LT);
+      for (i=IM_LT; i<=IM_GE; i++)  /* ORDER IM */
+        fillvalids(i, luaA_Address(func));
+      replace = typeFB;
+      break;
+    }
+    default: {
+      int e;
+      if ((e = luaO_findstring(name, luaT_eventname)) >= 0) {
+        oldfunc = *luaT_getim(LUA_T_LINE, e);
+        fillvalids(e, luaA_Address(func));
+        replace = (e == IM_GC || e == IM_INDEX) ? nilFB : typeFB;
+      }
+      else {
+        luaL_verror("`%.50s' is not a valid fallback name", name);
+        replace = NULL;  /* to avoid warnings */
+      }
+    }
+  }
+  if (oldfunc.ttype != LUA_T_NIL)
+    luaA_pushobject(&oldfunc);
+  else
+    lua_pushcfunction(replace);
+}
+#endif
+
diff --git a/ltm.h b/ltm.h
@@ -0,0 +1,61 @@
+/*
+** $Id: $
+** Tag methods
+** See Copyright Notice in lua.h
+*/
+
+#ifndef ltm_h
+#define ltm_h
+
+
+#include "lobject.h"
+
+/*
+* WARNING: if you change the order of this enumeration,
+* grep "ORDER IM"
+*/
+typedef enum {
+  IM_GETTABLE = 0,
+  IM_SETTABLE,
+  IM_INDEX,
+  IM_GETGLOBAL,
+  IM_SETGLOBAL,
+  IM_ADD,
+  IM_SUB,
+  IM_MUL,
+  IM_DIV,
+  IM_POW,
+  IM_UNM,
+  IM_LT,
+  IM_LE,
+  IM_GT,
+  IM_GE,
+  IM_CONCAT,
+  IM_GC,
+  IM_FUNCTION
+} IMS;
+
+#define IM_N 18
+
+
+extern struct IM {
+  TObject int_method[IM_N];
+} *luaT_IMtable;
+
+
+#define luaT_getim(tag,event) (&luaT_IMtable[-(tag)].int_method[event])
+#define luaT_getimbyObj(o,e)  (luaT_getim(luaT_efectivetag(o),(e)))
+
+extern char *luaT_eventname[];
+
+
+void luaT_settag (int tag, TObject *o);
+void luaT_realtag (int tag);
+int luaT_efectivetag (TObject *o);
+void luaT_settagmethod (int t, char *event, TObject *func);
+TObject *luaT_gettagmethod (int t, char *event);
+char *luaT_travtagmethods (int (*fn)(TObject *));
+
+void luaT_setfallback (void);  /* only if LUA_COMPAT2_5 */
+
+#endif