/*
** $Id: ltm.c,v 2.14 2011/06/02 19:31:40 roberto Exp $
** Tag methods
** See Copyright Notice in lua.h
*/


#include <string.h>

#define ltm_c
#define LUA_CORE

#include "lua.h"

#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"


static const char udatatypename[] = "userdata";

LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTAGS] = {
    "no value",
    "nil", "boolean", udatatypename, "number",
    "string", "table", "function", udatatypename, "thread",
    "proto", "upval"  /* these last two cases are used for tests only */
};


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


/*
** 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_getstr(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 (ttypenv(o)) {
        case LUA_TTABLE:
            mt = hvalue(o)->metatable;
            break;
        case LUA_TUSERDATA:
            mt = uvalue(o)->metatable;
            break;
        default:
            mt = G(L)->mt[ttypenv(o)];
    }
    return (mt ? luaH_getstr(mt, G(L)->tmname[event]) : luaO_nilobject);
}

