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  1. /*
  2. ** $Id: ltm.c $
  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 "lgc.h"
  20. #include "lobject.h"
  21. #include "lstate.h"
  22. #include "lstring.h"
  23. #include "ltable.h"
  24. #include "ltm.h"
  25. #include "lvm.h"
  26.  
  27.  
  28. static const char udatatypename[] = "userdata";
  29.  
  30. LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTYPES] = {
  31.   "no value",
  32.   "nil", "boolean", udatatypename, "number",
  33.   "string", "table", "function", udatatypename, "thread",
  34.   "upvalue", "proto" /* these last cases are used for tests only */
  35. };
  36.  
  37.  
  38. void luaT_init (lua_State *L) {
  39.   static const char *const luaT_eventname[] = {  /* ORDER TM */
  40.     "__index", "__newindex",
  41.     "__gc", "__mode", "__len", "__eq",
  42.     "__add", "__sub", "__mul", "__mod", "__pow",
  43.     "__div", "__idiv",
  44.     "__band", "__bor", "__bxor", "__shl", "__shr",
  45.     "__unm", "__bnot", "__lt", "__le",
  46.     "__concat", "__call", "__close"
  47.   };
  48.   int i;
  49.   for (i=0; i<TM_N; i++) {
  50.     G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);
  51.     luaC_fix(L, obj2gco(G(L)->tmname[i]));  /* never collect these names */
  52.   }
  53. }
  54.  
  55.  
  56. /*
  57. ** function to be used with macro "fasttm": optimized for absence of
  58. ** tag methods
  59. */
  60. const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {
  61.   const TValue *tm = luaH_getshortstr(events, ename);
  62.   lua_assert(event <= TM_EQ);
  63.   if (notm(tm)) {  /* no tag method? */
  64.     events->flags |= cast_byte(1u<<event);  /* cache this fact */
  65.     return NULL;
  66.   }
  67.   else return tm;
  68. }
  69.  
  70.  
  71. const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
  72.   Table *mt;
  73.   switch (ttype(o)) {
  74.     case LUA_TTABLE:
  75.       mt = hvalue(o)->metatable;
  76.       break;
  77.     case LUA_TUSERDATA:
  78.       mt = uvalue(o)->metatable;
  79.       break;
  80.     default:
  81.       mt = G(L)->mt[ttype(o)];
  82.   }
  83.   return (mt ? luaH_getshortstr(mt, G(L)->tmname[event]) : &G(L)->nilvalue);
  84. }
  85.  
  86.  
  87. /*
  88. ** Return the name of the type of an object. For tables and userdata
  89. ** with metatable, use their '__name' metafield, if present.
  90. */
  91. const char *luaT_objtypename (lua_State *L, const TValue *o) {
  92.   Table *mt;
  93.   if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||
  94.       (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {
  95.     const TValue *name = luaH_getshortstr(mt, luaS_new(L, "__name"));
  96.     if (ttisstring(name))  /* is '__name' a string? */
  97.       return getstr(tsvalue(name));  /* use it as type name */
  98.   }
  99.   return ttypename(ttype(o));  /* else use standard type name */
  100. }
  101.  
  102.  
  103. void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
  104.                   const TValue *p2, const TValue *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.   setobj2s(L, func + 3, p3);  /* 3rd argument */
  110.   L->top = func + 4;
  111.   /* metamethod may yield only when called from Lua code */
  112.   if (isLuacode(L->ci))
  113.     luaD_call(L, func, 0);
  114.   else
  115.     luaD_callnoyield(L, func, 0);
  116. }
  117.  
  118.  
  119. void luaT_callTMres (lua_State *L, const TValue *f, const TValue *p1,
  120.                      const TValue *p2, StkId res) {
  121.   ptrdiff_t result = savestack(L, res);
  122.   StkId func = L->top;
  123.   setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
  124.   setobj2s(L, func + 1, p1);  /* 1st argument */
  125.   setobj2s(L, func + 2, p2);  /* 2nd argument */
  126.   L->top += 3;
  127.   /* metamethod may yield only when called from Lua code */
  128.   if (isLuacode(L->ci))
  129.     luaD_call(L, func, 1);
  130.   else
  131.     luaD_callnoyield(L, func, 1);
  132.   res = restorestack(L, result);
  133.   setobjs2s(L, res, --L->top);  /* move result to its place */
  134. }
  135.  
  136.  
  137. static int callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
  138.                       StkId res, TMS event) {
  139.   const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
  140.   if (notm(tm))
  141.     tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
  142.   if (notm(tm)) return 0;
  143.   luaT_callTMres(L, tm, p1, p2, res);
  144.   return 1;
  145. }
  146.  
  147.  
  148. void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
  149.                     StkId res, TMS event) {
  150.   if (l_unlikely(!callbinTM(L, p1, p2, res, event))) {
  151.     switch (event) {
  152.       case TM_BAND: case TM_BOR: case TM_BXOR:
  153.       case TM_SHL: case TM_SHR: case TM_BNOT: {
  154.         if (ttisnumber(p1) && ttisnumber(p2))
  155.           luaG_tointerror(L, p1, p2);
  156.         else
  157.           luaG_opinterror(L, p1, p2, "perform bitwise operation on");
  158.       }
  159.       /* calls never return, but to avoid warnings: *//* FALLTHROUGH */
  160.       default:
  161.         luaG_opinterror(L, p1, p2, "perform arithmetic on");
  162.     }
  163.   }
  164. }
  165.  
  166.  
  167. void luaT_tryconcatTM (lua_State *L) {
  168.   StkId top = L->top;
  169.   if (l_unlikely(!callbinTM(L, s2v(top - 2), s2v(top - 1), top - 2,
  170.                                TM_CONCAT)))
  171.     luaG_concaterror(L, s2v(top - 2), s2v(top - 1));
  172. }
  173.  
  174.  
  175. void luaT_trybinassocTM (lua_State *L, const TValue *p1, const TValue *p2,
  176.                                        int flip, StkId res, TMS event) {
  177.   if (flip)
  178.     luaT_trybinTM(L, p2, p1, res, event);
  179.   else
  180.     luaT_trybinTM(L, p1, p2, res, event);
  181. }
  182.  
  183.  
  184. void luaT_trybiniTM (lua_State *L, const TValue *p1, lua_Integer i2,
  185.                                    int flip, StkId res, TMS event) {
  186.   TValue aux;
  187.   setivalue(&aux, i2);
  188.   luaT_trybinassocTM(L, p1, &aux, flip, res, event);
  189. }
  190.  
  191.  
  192. /*
  193. ** Calls an order tag method.
  194. ** For lessequal, LUA_COMPAT_LT_LE keeps compatibility with old
  195. ** behavior: if there is no '__le', try '__lt', based on l <= r iff
  196. ** !(r < l) (assuming a total order). If the metamethod yields during
  197. ** this substitution, the continuation has to know about it (to negate
  198. ** the result of r<l); bit CIST_LEQ in the call status keeps that
  199. ** information.
  200. */
  201. int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
  202.                       TMS event) {
  203.   if (callbinTM(L, p1, p2, L->top, event))  /* try original event */
  204.     return !l_isfalse(s2v(L->top));
  205. #if defined(LUA_COMPAT_LT_LE)
  206.   else if (event == TM_LE) {
  207.       /* try '!(p2 < p1)' for '(p1 <= p2)' */
  208.       L->ci->callstatus |= CIST_LEQ;  /* mark it is doing 'lt' for 'le' */
  209.       if (callbinTM(L, p2, p1, L->top, TM_LT)) {
  210.         L->ci->callstatus ^= CIST_LEQ;  /* clear mark */
  211.         return l_isfalse(s2v(L->top));
  212.       }
  213.       /* else error will remove this 'ci'; no need to clear mark */
  214.   }
  215. #endif
  216.   luaG_ordererror(L, p1, p2);  /* no metamethod found */
  217.   return 0;  /* to avoid warnings */
  218. }
  219.  
  220.  
  221. int luaT_callorderiTM (lua_State *L, const TValue *p1, int v2,
  222.                        int flip, int isfloat, TMS event) {
  223.   TValue aux; const TValue *p2;
  224.   if (isfloat) {
  225.     setfltvalue(&aux, cast_num(v2));
  226.   }
  227.   else
  228.     setivalue(&aux, v2);
  229.   if (flip) {  /* arguments were exchanged? */
  230.     p2 = p1; p1 = &aux;  /* correct them */
  231.   }
  232.   else
  233.     p2 = &aux;
  234.   return luaT_callorderTM(L, p1, p2, event);
  235. }
  236.  
  237.  
  238. void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
  239.                          const Proto *p) {
  240.   int i;
  241.   int actual = cast_int(L->top - ci->func) - 1;  /* number of arguments */
  242.   int nextra = actual - nfixparams;  /* number of extra arguments */
  243.   ci->u.l.nextraargs = nextra;
  244.   luaD_checkstack(L, p->maxstacksize + 1);
  245.   /* copy function to the top of the stack */
  246.   setobjs2s(L, L->top++, ci->func);
  247.   /* move fixed parameters to the top of the stack */
  248.   for (i = 1; i <= nfixparams; i++) {
  249.     setobjs2s(L, L->top++, ci->func + i);
  250.     setnilvalue(s2v(ci->func + i));  /* erase original parameter (for GC) */
  251.   }
  252.   ci->func += actual + 1;
  253.   ci->top += actual + 1;
  254.   lua_assert(L->top <= ci->top && ci->top <= L->stack_last);
  255. }
  256.  
  257.  
  258. void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
  259.   int i;
  260.   int nextra = ci->u.l.nextraargs;
  261.   if (wanted < 0) {
  262.     wanted = nextra;  /* get all extra arguments available */
  263.     checkstackGCp(L, nextra, where);  /* ensure stack space */
  264.     L->top = where + nextra;  /* next instruction will need top */
  265.   }
  266.   for (i = 0; i < wanted && i < nextra; i++)
  267.     setobjs2s(L, where + i, ci->func - nextra + i);
  268.   for (; i < wanted; i++)   /* complete required results with nil */
  269.     setnilvalue(s2v(where + i));
  270. }
  271.  
  272.