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      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 
     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 */
     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 
     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 */
     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 
    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 
    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 
    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 
    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