Function generic_reader

src/Chain/libraries/glua/lbaselib.cpp:430–444

** Reader for generic 'load' function: 'lua_load' uses the ** stack for internal stuff, so the reader cannot change the ** stack top. Instead, it keeps its resulting string in a ** reserved slot inside the stack. */

** reserved slot inside the stack.
*/
static const char *generic_reader(lua_State *L, void *ud, size_t *size) {
    (void)(ud);  /* not used */
    luaL_checkstack(L, 2, "too many nested functions");
    lua_pushvalue(L, 1);  /* get function */
    lua_call(L, 0, 1);  /* call it */
    if (lua_isnil(L, -1)) {
        lua_pop(L, 1);  /* pop result */
        *size = 0;
        return nullptr;
    }
    else if (!lua_isstring(L, -1))
        luaL_error(L, "reader function must return a string");
    lua_replace(L, RESERVEDSLOT);  /* save string in reserved slot */
    return lua_tolstring(L, RESERVEDSLOT, size);
}


static int luaB_load(lua_State *L) {