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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.