1 /*
2 ** $Id: ltm.c,v 2.38.1.1 2017/04/19 17:39:34 roberto Exp $
3 ** Tag methods
4 ** See Copyright Notice in lua.h
5 */
6 
7 #define ltm_c
8 #define LUA_CORE
9 
10 #include "lprefix.h"
11 
12 
13 #include <string.h>
14 
15 #include "lua.h"
16 
17 #include "ldebug.h"
18 #include "ldo.h"
19 #include "lobject.h"
20 #include "lstate.h"
21 #include "lstring.h"
22 #include "ltable.h"
23 #include "ltm.h"
24 #include "lvm.h"
25 
26 
27 static const char udatatypename[] = "userdata";
28 
29 LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTAGS] = {
30   "no value",
31   "nil", "boolean", udatatypename, "number",
32   "string", "table", "function", udatatypename, "thread",
33   "proto" /* this last case is used for tests only */
34 };
35 
36 
luaT_init(lua_State * L)37 void luaT_init (lua_State *L) {
38   static const char *const luaT_eventname[] = {  /* ORDER TM */
39     "__index", "__newindex",
40     "__gc", "__mode", "__len", "__eq",
41     "__add", "__sub", "__mul", "__mod", "__pow",
42     "__div", "__idiv",
43     "__band", "__bor", "__bxor", "__shl", "__shr",
44     "__unm", "__bnot", "__lt", "__le",
45     "__concat", "__call"
46   };
47   int i;
48   for (i=0; i<TM_N; i++) {
49     G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);
50     luaC_fix(L, obj2gco(G(L)->tmname[i]));  /* never collect these names */
51   }
52 }
53 
54 
55 /*
56 ** function to be used with macro "fasttm": optimized for absence of
57 ** tag methods
58 */
luaT_gettm(Table * events,TMS event,TString * ename)59 const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {
60   const TValue *tm = luaH_getshortstr(events, ename);
61   lua_assert(event <= TM_EQ);
62   if (ttisnil(tm)) {  /* no tag method? */
63     events->flags |= cast_byte(1u<<event);  /* cache this fact */
64     return NULL;
65   }
66   else return tm;
67 }
68 
69 
luaT_gettmbyobj(lua_State * L,const TValue * o,TMS event)70 const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
71   Table *mt;
72   switch (ttnov(o)) {
73     case LUA_TTABLE:
74       mt = hvalue(o)->metatable;
75       break;
76     case LUA_TUSERDATA:
77       mt = uvalue(o)->metatable;
78       break;
79     default:
80       mt = G(L)->mt[ttnov(o)];
81   }
82   return (mt ? luaH_getshortstr(mt, G(L)->tmname[event]) : luaO_nilobject);
83 }
84 
85 
86 /*
87 ** Return the name of the type of an object. For tables and userdata
88 ** with metatable, use their '__name' metafield, if present.
89 */
luaT_objtypename(lua_State * L,const TValue * o)90 const char *luaT_objtypename (lua_State *L, const TValue *o) {
91   Table *mt;
92   if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||
93       (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {
94     const TValue *name = luaH_getshortstr(mt, luaS_new(L, "__name"));
95     if (ttisstring(name))  /* is '__name' a string? */
96       return getstr(tsvalue(name));  /* use it as type name */
97   }
98   return ttypename(ttnov(o));  /* else use standard type name */
99 }
100 
101 
luaT_callTM(lua_State * L,const TValue * f,const TValue * p1,const TValue * p2,TValue * p3,int hasres)102 void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
103                   const TValue *p2, TValue *p3, int hasres) {
104   ptrdiff_t result = savestack(L, p3);
105   StkId func = L->top;
106   setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
107   setobj2s(L, func + 1, p1);  /* 1st argument */
108   setobj2s(L, func + 2, p2);  /* 2nd argument */
109   L->top += 3;
110   if (!hasres)  /* no result? 'p3' is third argument */
111     setobj2s(L, L->top++, p3);  /* 3rd argument */
112   /* metamethod may yield only when called from Lua code */
113   if (isLua(L->ci))
114     luaD_call(L, func, hasres);
115   else
116     luaD_callnoyield(L, func, hasres);
117   if (hasres) {  /* if has result, move it to its place */
118     p3 = restorestack(L, result);
119     setobjs2s(L, p3, --L->top);
120   }
121 }
122 
123 
luaT_callbinTM(lua_State * L,const TValue * p1,const TValue * p2,StkId res,TMS event)124 int luaT_callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
125                     StkId res, TMS event) {
126   const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
127   if (ttisnil(tm))
128     tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
129   if (ttisnil(tm)) return 0;
130   luaT_callTM(L, tm, p1, p2, res, 1);
131   return 1;
132 }
133 
134 
luaT_trybinTM(lua_State * L,const TValue * p1,const TValue * p2,StkId res,TMS event)135 void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
136                     StkId res, TMS event) {
137   if (!luaT_callbinTM(L, p1, p2, res, event)) {
138     switch (event) {
139       case TM_CONCAT:
140         luaG_concaterror(L, p1, p2);
141       /* call never returns, but to avoid warnings: *//* FALLTHROUGH */
142       case TM_BAND: case TM_BOR: case TM_BXOR:
143       case TM_SHL: case TM_SHR: case TM_BNOT: {
144         lua_Number dummy;
145         if (tonumber(p1, &dummy) && tonumber(p2, &dummy))
146           luaG_tointerror(L, p1, p2);
147         else
148           luaG_opinterror(L, p1, p2, "perform bitwise operation on");
149       }
150       /* calls never return, but to avoid warnings: *//* FALLTHROUGH */
151       default:
152         luaG_opinterror(L, p1, p2, "perform arithmetic on");
153     }
154   }
155 }
156 
157 
luaT_callorderTM(lua_State * L,const TValue * p1,const TValue * p2,TMS event)158 int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
159                       TMS event) {
160   if (!luaT_callbinTM(L, p1, p2, L->top, event))
161     return -1;  /* no metamethod */
162   else
163     return !l_isfalse(L->top);
164 }
165 
166