Lua 5.3.4 里的 ltm.c

#ifndef ltm_h
#define ltm_h


#include "lobject.h"


/*
* WARNING: if you change the order of this enumeration,
* grep "ORDER TM" and "ORDER OP"
*/
typedef enum {
  TM_INDEX,
  TM_NEWINDEX,
  TM_GC,
  TM_MODE,
  TM_LEN,
  TM_EQ,  /* last tag method with fast access */
  TM_ADD,
  TM_SUB,
  TM_MUL,
  TM_MOD,
  TM_POW,
  TM_DIV,
  TM_IDIV,
  TM_BAND,
  TM_BOR,
  TM_BXOR,
  TM_SHL,
  TM_SHR,
  TM_UNM,
  TM_BNOT,
  TM_LT,
  TM_LE,
  TM_CONCAT,
  TM_CALL,
  TM_N    /* number of elements in the enum */
} TMS;



#define gfasttm(g,et,e) ((et) == NULL ? NULL : \
  ((et)->flags & (1u<<(e))) ? NULL : luaT_gettm(et, e, (g)->tmname[e]))

#define fasttm(l,et,e)  gfasttm(G(l), et, e)

#define ttypename(x)  luaT_typenames_[(x) + 1]

LUAI_DDEC const char *const luaT_typenames_[LUA_TOTALTAGS];


LUAI_FUNC const char *luaT_objtypename (lua_State *L, const TValue *o);

LUAI_FUNC const TValue *luaT_gettm (Table *events, TMS event, TString *ename);
LUAI_FUNC const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o,
                                                       TMS event);
LUAI_FUNC void luaT_init (lua_State *L);

LUAI_FUNC void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
                            const TValue *p2, TValue *p3, int hasres);
LUAI_FUNC int luaT_callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
                              StkId res, TMS event);
LUAI_FUNC void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
                              StkId res, TMS event);
LUAI_FUNC int luaT_callorderTM (lua_State *L, const TValue *p1,
                                const TValue *p2, TMS event);



#endif

/*
** Return the name of the type of an object. For tables and userdata
** with metatable, use their '__name' metafield, if present.
*/
const char *luaT_objtypename (lua_State *L, const TValue *o) {
  Table *mt;
  if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||
      (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {
    const TValue *name = luaH_getshortstr(mt, luaS_new(L, "__name"));
    if (ttisstring(name))  /* is '__name' a string? */
      return getstr(tsvalue(name));  /* use it as type name */
  }
  return ttypename(ttnov(o));  /* else use standard type name */
}

#define gfasttm(g,et,e) ((et) == NULL ? NULL : \
  ((et)->flags & (1u<<(e))) ? NULL : luaT_gettm(et, e, (g)->tmname[e]))

#define fasttm(l,et,e)  gfasttm(G(l), et, e)

/*
** function to be used with macro "fasttm": optimized for absence of
** tag methods
*/
const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {
  const TValue *tm = luaH_getshortstr(events, ename);
  lua_assert(event <= TM_EQ);
  if (ttisnil(tm)) {  /* no tag method? */
    events->flags |= cast_byte(1u<<event);  /* cache this fact */
    return NULL;
  }
  else return tm;
}

const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
  Table *mt;
  switch (ttnov(o)) {
    case LUA_TTABLE:
      mt = hvalue(o)->metatable;
      break;
    case LUA_TUSERDATA:
      mt = uvalue(o)->metatable;
      break;
    default:
      mt = G(L)->mt[ttnov(o)];
  }
  return (mt ? luaH_getshortstr(mt, G(L)->tmname[event]) : luaO_nilobject);
}

void luaT_init (lua_State *L) {
  static const char *const luaT_eventname[] = {  /* ORDER TM */
    "__index", "__newindex",
    "__gc", "__mode", "__len", "__eq",
    "__add", "__sub", "__mul", "__mod", "__pow",
    "__div", "__idiv",
    "__band", "__bor", "__bxor", "__shl", "__shr",
    "__unm", "__bnot", "__lt", "__le",
    "__concat", "__call"
  };
  int i;
  for (i=0; i<TM_N; i++) {
    G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);
    luaC_fix(L, obj2gco(G(L)->tmname[i]));  /* never collect these names */
  }
}

void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
                  const TValue *p2, TValue *p3, int hasres) {
  ptrdiff_t result = savestack(L, p3);
  StkId func = L->top;
  setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
  setobj2s(L, func + 1, p1);  /* 1st argument */
  setobj2s(L, func + 2, p2);  /* 2nd argument */
  L->top += 3;
  if (!hasres)  /* no result? 'p3' is third argument */
    setobj2s(L, L->top++, p3);  /* 3rd argument */
  /* metamethod may yield only when called from Lua code */
  if (isLua(L->ci))
    luaD_call(L, func, hasres);
  else
    luaD_callnoyield(L, func, hasres);
  if (hasres) {  /* if has result, move it to its place */
    p3 = restorestack(L, result);
    setobjs2s(L, p3, --L->top);
  }
}

int luaT_callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
                    StkId res, TMS event) {
  const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
  if (ttisnil(tm))
    tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
  if (ttisnil(tm)) return 0;
  luaT_callTM(L, tm, p1, p2, res, 1);
  return 1;
}

void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
                    StkId res, TMS event) {
  if (!luaT_callbinTM(L, p1, p2, res, event)) {
    switch (event) {
      case TM_CONCAT:
        luaG_concaterror(L, p1, p2);
      /* call never returns, but to avoid warnings: *//* FALLTHROUGH */
      case TM_BAND: case TM_BOR: case TM_BXOR:
      case TM_SHL: case TM_SHR: case TM_BNOT: {
        lua_Number dummy;
        if (tonumber(p1, &dummy) && tonumber(p2, &dummy))
          luaG_tointerror(L, p1, p2);
        else
          luaG_opinterror(L, p1, p2, "perform bitwise operation on");
      }
      /* calls never return, but to avoid warnings: *//* FALLTHROUGH */
      default:
        luaG_opinterror(L, p1, p2, "perform arithmetic on");
    }
  }
}

int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
                      TMS event) {
  if (!luaT_callbinTM(L, p1, p2, L->top, event))
    return -1;  /* no metamethod */
  else
    return !l_isfalse(L->top);
}