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ltm.c (8528B)

      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_Hgetshortstr(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_Hgetshortstr(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_Hgetshortstr(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.p;
    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.p = 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 lu_byte 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.p;
    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.p += 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.p);  /* move result to its place */
    134   return ttypetag(s2v(res));  /* return tag of the result */
    135 }
    136 
    137 
    138 static int callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
    139                       StkId res, TMS event) {
    140   const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
    141   if (notm(tm))
    142     tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
    143   if (notm(tm))
    144     return -1;  /* tag method not found */
    145   else  /* call tag method and return the tag of the result */
    146     return luaT_callTMres(L, tm, p1, p2, res);
    147 }
    148 
    149 
    150 void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
    151                     StkId res, TMS event) {
    152   if (l_unlikely(callbinTM(L, p1, p2, res, event) < 0)) {
    153     switch (event) {
    154       case TM_BAND: case TM_BOR: case TM_BXOR:
    155       case TM_SHL: case TM_SHR: case TM_BNOT: {
    156         if (ttisnumber(p1) && ttisnumber(p2))
    157           luaG_tointerror(L, p1, p2);
    158         else
    159           luaG_opinterror(L, p1, p2, "perform bitwise operation on");
    160       }
    161       /* calls never return, but to avoid warnings: *//* FALLTHROUGH */
    162       default:
    163         luaG_opinterror(L, p1, p2, "perform arithmetic on");
    164     }
    165   }
    166 }
    167 
    168 
    169 /*
    170 ** The use of 'p1' after 'callbinTM' is safe because, when a tag
    171 ** method is not found, 'callbinTM' cannot change the stack.
    172 */
    173 void luaT_tryconcatTM (lua_State *L) {
    174   StkId p1 = L->top.p - 2;  /* first argument */
    175   if (l_unlikely(callbinTM(L, s2v(p1), s2v(p1 + 1), p1, TM_CONCAT) < 0))
    176     luaG_concaterror(L, s2v(p1), s2v(p1 + 1));
    177 }
    178 
    179 
    180 void luaT_trybinassocTM (lua_State *L, const TValue *p1, const TValue *p2,
    181                                        int flip, StkId res, TMS event) {
    182   if (flip)
    183     luaT_trybinTM(L, p2, p1, res, event);
    184   else
    185     luaT_trybinTM(L, p1, p2, res, event);
    186 }
    187 
    188 
    189 void luaT_trybiniTM (lua_State *L, const TValue *p1, lua_Integer i2,
    190                                    int flip, StkId res, TMS event) {
    191   TValue aux;
    192   setivalue(&aux, i2);
    193   luaT_trybinassocTM(L, p1, &aux, flip, res, event);
    194 }
    195 
    196 
    197 /*
    198 ** Calls an order tag method.
    199 ** For lessequal, LUA_COMPAT_LT_LE keeps compatibility with old
    200 ** behavior: if there is no '__le', try '__lt', based on l <= r iff
    201 ** !(r < l) (assuming a total order). If the metamethod yields during
    202 ** this substitution, the continuation has to know about it (to negate
    203 ** the result of r<l); bit CIST_LEQ in the call status keeps that
    204 ** information.
    205 */
    206 int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
    207                       TMS event) {
    208   int tag = callbinTM(L, p1, p2, L->top.p, event);  /* try original event */
    209   if (tag >= 0)  /* found tag method? */
    210     return !tagisfalse(tag);
    211 #if defined(LUA_COMPAT_LT_LE)
    212   else if (event == TM_LE) {
    213     /* try '!(p2 < p1)' for '(p1 <= p2)' */
    214     L->ci->callstatus |= CIST_LEQ;  /* mark it is doing 'lt' for 'le' */
    215     tag = callbinTM(L, p2, p1, L->top.p, TM_LT);
    216     L->ci->callstatus ^= CIST_LEQ;  /* clear mark */
    217     if (tag >= 0)  /* found tag method? */
    218       return tagisfalse(tag);
    219   }
    220 #endif
    221   luaG_ordererror(L, p1, p2);  /* no metamethod found */
    222   return 0;  /* to avoid warnings */
    223 }
    224 
    225 
    226 int luaT_callorderiTM (lua_State *L, const TValue *p1, int v2,
    227                        int flip, int isfloat, TMS event) {
    228   TValue aux; const TValue *p2;
    229   if (isfloat) {
    230     setfltvalue(&aux, cast_num(v2));
    231   }
    232   else
    233     setivalue(&aux, v2);
    234   if (flip) {  /* arguments were exchanged? */
    235     p2 = p1; p1 = &aux;  /* correct them */
    236   }
    237   else
    238     p2 = &aux;
    239   return luaT_callorderTM(L, p1, p2, event);
    240 }
    241 
    242 
    243 void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
    244                          const Proto *p) {
    245   int i;
    246   int actual = cast_int(L->top.p - ci->func.p) - 1;  /* number of arguments */
    247   int nextra = actual - nfixparams;  /* number of extra arguments */
    248   ci->u.l.nextraargs = nextra;
    249   luaD_checkstack(L, p->maxstacksize + 1);
    250   /* copy function to the top of the stack */
    251   setobjs2s(L, L->top.p++, ci->func.p);
    252   /* move fixed parameters to the top of the stack */
    253   for (i = 1; i <= nfixparams; i++) {
    254     setobjs2s(L, L->top.p++, ci->func.p + i);
    255     setnilvalue(s2v(ci->func.p + i));  /* erase original parameter (for GC) */
    256   }
    257   ci->func.p += actual + 1;
    258   ci->top.p += actual + 1;
    259   lua_assert(L->top.p <= ci->top.p && ci->top.p <= L->stack_last.p);
    260 }
    261 
    262 
    263 void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
    264   int i;
    265   int nextra = ci->u.l.nextraargs;
    266   if (wanted < 0) {
    267     wanted = nextra;  /* get all extra arguments available */
    268     checkstackp(L, nextra, where);  /* ensure stack space */
    269     L->top.p = where + nextra;  /* next instruction will need top */
    270   }
    271   for (i = 0; i < wanted && i < nextra; i++)
    272     setobjs2s(L, where + i, ci->func.p - nextra + i);
    273   for (; i < wanted; i++)   /* complete required results with nil */
    274     setnilvalue(s2v(where + i));
    275 }
    276