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1 /*
2 ** $Id: ltm.c,v 2.14.1.1 2013/04/12 18:48:47 roberto Exp $
3 ** Tag methods
4 ** See Copyright Notice in lua.h
5 */
6 
7 
8 #include <string.h>
9 
10 #define ltm_c
11 #define LUA_CORE
12 
13 #include "lua.h"
14 
15 #include "lobject.h"
16 #include "lstate.h"
17 #include "lstring.h"
18 #include "ltable.h"
19 #include "ltm.h"
20 
21 
22 static const char udatatypename[] = "userdata";
23 
24 LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTAGS] = {
25   "no value",
26   "nil", "boolean", udatatypename, "number",
27   "string", "table", "function", udatatypename, "thread",
28   "proto", "upval"  /* these last two cases are used for tests only */
29 };
30 
31 
luaT_init(lua_State * L)32 void luaT_init (lua_State *L) {
33   static const char *const luaT_eventname[] = {  /* ORDER TM */
34     "__index", "__newindex",
35     "__gc", "__mode", "__len", "__eq",
36     "__add", "__sub", "__mul", "__div", "__mod",
37     "__pow", "__unm", "__lt", "__le",
38     "__concat", "__call"
39   };
40   int i;
41   for (i=0; i<TM_N; i++) {
42     G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);
43     luaS_fix(G(L)->tmname[i]);  /* never collect these names */
44   }
45 }
46 
47 
48 /*
49 ** function to be used with macro "fasttm": optimized for absence of
50 ** tag methods
51 */
luaT_gettm(Table * events,TMS event,TString * ename)52 const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {
53   const TValue *tm = luaH_getstr(events, ename);
54   lua_assert(event <= TM_EQ);
55   if (ttisnil(tm)) {  /* no tag method? */
56     events->flags |= cast_byte(1u<<event);  /* cache this fact */
57     return NULL;
58   }
59   else return tm;
60 }
61 
62 
luaT_gettmbyobj(lua_State * L,const TValue * o,TMS event)63 const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
64   Table *mt;
65   switch (ttypenv(o)) {
66     case LUA_TTABLE:
67       mt = hvalue(o)->metatable;
68       break;
69     case LUA_TUSERDATA:
70       mt = uvalue(o)->metatable;
71       break;
72     default:
73       mt = G(L)->mt[ttypenv(o)];
74   }
75   return (mt ? luaH_getstr(mt, G(L)->tmname[event]) : luaO_nilobject);
76 }
77 
78