Lua2RTT/lua-5.3.4/ltm.c

/*
** $Id: ltm.c,v 2.38 2016/12/22 13:08:50 roberto Exp $
** Tag methods
** See Copyright Notice in lua.h
*/

#define ltm_c
#define LUA_CORE

#include "lprefix.h"


#include <string.h>

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lvm.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" /* this last case is 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", "__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 */
    }
}


/*
** 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);
}


/*
** 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 */
}


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);
}