Less annoying luaL_Buffer handling in C++

example.cpp

int l_imwrite(lua_State *L)
{
    // see https://gist.github.com/4154182
    cv::Mat *img = LuaProxy<cv::Mat>::get(L, 1);
    const char *path = luaL_checkstring(L, 2);

    if (cv::imwrite(path, *img))
    {
        lua_pushboolean(L, true);
        return 1;
    }
    // else
    lua_pushnil(L);
    LuaBuffer(L).add("Cannot write image to `").add(path).add("'.").finish();
    return 2;
}

lua_buffer.hpp

#pragma once
#include <lua.hpp>

// Note: This is incomplete, as it misses luaL_addchar, luaL_addlstring, etc.
//       but still covers 100% of my use cases ;)
struct LuaBuffer
{
    luaL_Buffer b;
    LuaBuffer(lua_State *L)
    {
        luaL_buffinit(L, &b);
    }

    inline LuaBuffer &add(const char *s)
    {
        luaL_addstring(&b, s);
        return *this;
    }

    inline LuaBuffer &addvalue()
    {
        luaL_addvalue(&b);
        return *this;
    }

    inline void finish()
    {
        luaL_pushresult(&b);
    }
};