Function push_result_size 

pub fn push_result_size(
    state: &mut LuaState,
    buf: &mut LuaBuffer,
    sz: usize,
) -> Result<(), LuaError>

Add sz bytes to the buffer count then call push_result.

C: LUALIB_API void luaL_pushresultsize(luaL_Buffer *B, size_t sz)