[dFF]

Ok, thank you for reply. Also if anybody still have minor confusion can see the natives source.

Spoiler

Engine:

int is_ent_valid(int iEnt)
{
    if (iEnt < 1 || iEnt > gpGlobals->maxEntities) 
        return 0;

    if (iEnt <= gpGlobals->maxClients)
    {
        if (!MF_IsPlayerIngame(iEnt))
        {
            return 0;
        }
    } else {
        if (FNullEnt(INDEXENT(iEnt)))
        {
            return 0;
        }
    }

    return 1;
}

static cell AMX_NATIVE_CALL is_valid_ent(AMX *amx, cell *params)
{
    return is_ent_valid(params[1]);
}

static cell AMX_NATIVE_CALL entity_set_origin(AMX *amx, cell *params)
{
    int iEnt = params[1];

    CHECK_ENTITY_SIMPLE(iEnt);
    
    edict_t *pEnt = INDEXENT2(iEnt);
    cell *vVector = MF_GetAmxAddr(amx, params[2]);
    REAL fX = amx_ctof(vVector[0]);
    REAL fY = amx_ctof(vVector[1]);
    REAL fZ = amx_ctof(vVector[2]);
    Vector vOrigin = Vector(fX, fY, fZ);

    SET_SIZE(pEnt, pEnt->v.mins, pEnt->v.maxs);
    SET_ORIGIN(pEnt, vOrigin);

    return 1;
}

Spoiler

Fakemeta:

// pev_valid
static cell AMX_NATIVE_CALL amx_pev_valid(AMX *amx, cell *params)
{
    int idx = static_cast<int>(params[1]);

    edict_t *e = INDEXENT(idx);

    if (FNullEnt(e))
        return 0;

    if (e->pvPrivateData)
        return 2;

    return 1;
}

#define CHECK_ENTITY(x) if (x != 0 && (FNullEnt(INDEXENT_NEW(x)) || x < 0 || x > gpGlobals->maxEntities)) return 0;

static cell AMX_NATIVE_CALL engfunc(AMX *amx, cell *params)
{
    .... some code ....
    // pfnSetOrigin
    case    EngFunc_SetOrigin:            // void )                (edict_t *e, const float *rgflOrigin);
        cRet = MF_GetAmxAddr(amx,params[2]);
        index = cRet[0];
        CHECK_ENTITY(index);
        cRet = MF_GetAmxAddr(amx,params[3]);
        Vec1[0]=amx_ctof(cRet[0]);
        Vec1[1]=amx_ctof(cRet[1]);
        Vec1[2]=amx_ctof(cRet[2]);
        (*g_engfuncs.pfnSetOrigin)(INDEXENT2(index),Vec1);
        return 1;
}