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<a href="/categories/#lua之基础" title="lua之基础">lua之基础</a>

“翻译”自https://github.com/SteveKChiu/lua-intf

lua-intf 提供了C++11 与Lua 语言之间的一种绑定机制，它提供了三种不同的API（本文只会讲到LuaBinding 与LuaRef）

LuaBinding：导出C++ 类、函数给Lua 脚本使用
LuaRef：用于访问Lua Object 的高级别API
LuaState：为Lua C API 提供的低级别包装器

除了C++11、Lua 之外，lua-intf 没有其他需要依赖的。而且它是一个只有头文件的库，也就是说没有makefile 或者其他安装操作，直接拷贝lua-intf 源码到你的项目中，在代码中#include LuaIntf.h 即可

Lua 和C++ 的错误处理

使用LuaIntf，最好使用C++ 编译器编译Lua，这样允许Lua 库在出现错误时抛出异常，而且保证栈上的C++ 对象被正确的析构

更多关于错误处理的内容，可以参见http://lua-users.org/wiki/ErrorHandlingBetweenLuaAndCplusplus

如果你坚持想在C 环境下编译Lua，而且可以忍受longjump 问题，你可以在#include LuaIntf.h 头文件之前先#define LUAINTF_LINK_LUA_COMPILED_IN_CXX 0

#define LUAINTF_LINK_LUA_COMPILED_IN_CXX 0
#include "LuaIntf/LuaIntf.h"

在C++ 环境下编译Lua

预编译的Lua 库大多数发行版都是在C 环境下编译的，如果需要在C++ 环境下编译Lua 库，你可能需要自己手动操作。在C++ 环境下编译Lua 其实也很简单，首先先把Lua 源码下载下来

curl http://www.lua.org/ftp/lua-5.3.0.tar.gz -o lua-5.3.0.tar.gz
tar xf lua-5.3.0.tar.gz
cd lua-5.3.0

在不同的环境下使用不同的命令进行编译构建

# Linux环境下编译
make linux MYCFLAGS="-x c++" CC="g++"
# Mac OSX 环境下编译

make macosx MYCFLAGS="-x c++" MYLDFLAGS="-lc++"
## 在Windows 下用MINGW 或MSYS 编译

make mingw MYCFLAGS="-x c++" CC="g++"

而且你可以选择指定路径进行安装

make install INSTALL_TOP=<path>

为Lua 脚本导出C++ 类或函数

比如下面这个C++ 类

class Web
{
public:
    // base_url is optional
    Web(const std::string &base_url);
    ~Web();
<span class="k">static</span> <span class="kt">void</span> <span class="n">go_home</span><span class="p">();</span>

<span class="k">static</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">home_url</span><span class="p">();</span>
<span class="k">static</span> <span class="kt">void</span> <span class="n">set_home_url</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="o">&amp;</span><span class="n">url</span><span class="p">);</span>

<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">url</span><span class="p">()</span> <span class="k">const</span><span class="p">;</span>
<span class="kt">void</span> <span class="n">set_url</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="o">&amp;</span><span class="n">url</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">resolve_url</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="o">&amp;</span><span class="n">uri</span><span class="p">);</span>

<span class="c1">// doing reload if uri is empty

    std::string load(const std::string &uri);

}

使用下面的代码可以将Web 类导出

LuaBinding(L).beginClass<Web>("Web")
    .addConstructor(LUA_ARGS(_opt<std::string>))
    .addStaticProperty("home_url", &Web::home_url, &Web::set_home_url)
    .addStaticFunction("go_home", &Web::go_home)
    .addProperty("url", &Web::url, &Web:set_url)
    .addFunction("resolve_url", &Web::resolve_url)
    .addFunction("load", &Web::load, LUA_ARGS(_opt<std::string>))
    .addStaticFunction("lambda", [] {
        // you can use C++11 lambda expression here too
        return "yes";
    })
.endClass();

在Lua 代码中可以这样使用Web 类

local w = Web()                            -- auto w = Web("");
w.url = "http://www.xumenger.com"          -- w.set_url("http://www.xumenger.com");
local page = w:load()                      -- auto page = w.load("");
page = w:load("http://www.google.com")     -- page = w.load("http://www.google.com");
local url = w.url                          -- auto url = w.url();

Lua 调用C++ 的例子

编写C++ 代码simplelog.cpp，如下

#define LUAINTF_LINK_LUA_COMPILED_IN_CXX 0
#include "LuaIntf/LuaIntf.h"

#include <iostream>
#include <lua.hpp>
#include <string>

using namespace std;
struct lua_State;
class SimpleLog {

public:

static SimpleLog *getInstance() {

static SimpleLog instance;

return &instance;

}
<span class="o">~</span><span class="n">SimpleLog</span><span class="p">();</span>
<span class="kt">void</span> <span class="n">Log</span><span class="p">(</span><span class="k">const</span> <span class="n">string</span> <span class="o">&amp;</span><span class="n">str</span><span class="p">);</span>
<span class="kt">void</span> <span class="n">BindLua</span><span class="p">(</span><span class="n">lua_State</span> <span class="o">*</span><span class="n">L</span><span class="p">);</span>

private:

SimpleLog();

};
SimpleLog::SimpleLog() {}

SimpleLog::~SimpleLog() {}
void SimpleLog::Log(const string &str) {

cout << "C++ Env: SimpleLog::Log() " << str << endl;

}
namespace {

using LuaRef = LuaIntf::LuaRef;
<span class="kt">void</span> <span class="nf">LuaLog</span><span class="p">(</span><span class="k">const</span> <span class="n">string</span> <span class="o">&amp;</span><span class="n">str</span><span class="p">)</span> <span class="p">{</span>
    <span class="n">SimpleLog</span><span class="o">::</span><span class="n">getInstance</span><span class="p">()</span><span class="o">-&gt;</span><span class="n">Log</span><span class="p">(</span><span class="n">str</span><span class="p">);</span>
<span class="p">}</span>

<span class="k">namespace</span> <span class="n">LuaSimpleLog</span> <span class="p">{</span>
    <span class="kt">void</span> <span class="n">Bind</span><span class="p">(</span><span class="n">lua_State</span> <span class="o">*</span><span class="n">L</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">assert</span><span class="p">(</span><span class="n">L</span><span class="p">);</span>
        <span class="n">LuaIntf</span><span class="o">::</span><span class="n">LuaBinding</span><span class="p">(</span><span class="n">L</span><span class="p">).</span><span class="n">beginModule</span><span class="p">(</span><span class="s">&#34;simple_log&#34;</span><span class="p">)</span>
                 <span class="p">.</span><span class="n">addFunction</span><span class="p">(</span><span class="s">&#34;log&#34;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">LuaLog</span><span class="p">)</span>
                 <span class="p">.</span><span class="n">endModule</span><span class="p">();</span>
    <span class="p">}</span>
<span class="p">};</span>

};
void SimpleLog::BindLua(lua_State *L) {

LuaSimpleLog::Bind(L);

}
int main() {

lua_State *L = luaL_newstate();

luaL_openlibs(L);

SimpleLog::getInstance()->BindLua(L);

cout << "C++ Env: C++ main() start" << endl;

luaL_dofile(L, "./test.lua");

cout << "C++ Env: C++ main() end" << endl;

return 0;

}

编写log.lua 代码如下

local Log = {}
local log = simple_log.log
function Log:new(log_name)

assert("table"  type(self))

assert(not log_name or "string"  type(log_name))

local log = {}

log.log_name = log_name or "log"

setmetatable(log, self)

self.__index = self

return log

end
function Log:set_log_name(log_name)

self.log_name = log_name

end
function Log:info(pattern, …)

log(string.format(pattern, …))

end
function Log:debug()

print("Lua Env: log.lua debuf()")

end
return Log

编写test.lua 内容如下

local function main()
<span class="nb">print</span><span class="p">(</span><span class="s2">&#34;Lua Env: test.lua main() begin&#34;</span><span class="p">)</span>
<span class="kd">local</span> <span class="n">p</span> <span class="o">=</span> <span class="s2">&#34;../TestLuaIntf&#34;</span>
<span class="nb">package.path</span> <span class="o">=</span> <span class="nb">package.path</span> <span class="o">..</span> <span class="s2">&#34;;&#34;</span> <span class="o">..</span> <span class="n">p</span> <span class="o">..</span> <span class="s2">&#34;/&#34;</span> <span class="o">..</span> <span class="s2">&#34;TestLuaIntf&#34;</span> <span class="o">..</span> <span class="s2">&#34;/?.lua&#34;</span>

<span class="nb">print</span><span class="p">(</span><span class="s2">&#34;Lua Env: test.lua main() middle&#34;</span><span class="p">)</span>

<span class="kd">local</span> <span class="n">log</span> <span class="o">=</span> <span class="nb">require</span><span class="p">(</span><span class="s2">&#34;log&#34;</span><span class="p">):</span><span class="n">new</span><span class="p">(</span><span class="s2">&#34;svn_log&#34;</span><span class="p">)</span>
<span class="n">log</span><span class="p">:</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;Lua Env: test.lua main() call info() %d...&#34;</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>

<span class="nb">print</span><span class="p">(</span><span class="s2">&#34;Lua Env: test.lua main() end&#34;</span><span class="p">)</span>

end
xpcall(main, function(…)

local msg = {…};

for k, v in pairs(msg) do

print("Lua Env: k=" … tostring(k) … " v =" … tostring(v))

end

print("Lua Env: " … tostring() … " 123")

end)

编译C++ 程序运行效果如下

这个例子中的流程是通过C++ 调用lua 接口luaL_dofile(L, “./test.lua”) 来执行test.lua，test.lua 中require(“log”)，然后lua 再调用C++ 的函数Log 完成打印！

访问Lua Object 的高级别API

LuaRef 被设计用来方便地访问Lua 对象，而且大多数情况下你不需要像Lua 原生API那样处理Lua 栈

使用Lua 原生API 实现C++ 访问Lua 的代码要这样实现

lua_State *L = ...;
lua_getglobal(L, "module");
lua_getfield(L, -1, "method");
lua_pushintteger(L, 1);
lua_pushstring(L, "yes");
lua_pushboolean(L, true);
lua_call(L, 3, 0);

但如果使用LuaRef 那么就会非常简单

LuaRef fun(L, "module.method");
func(1, "yes", true);

访问Lua 中的表也是非常方便的

LuaRef table(L, "my_table");
table["value"] = 15;
int value = table.get<int>("value");
for(auto &e : table) {

std::string key = e.key<std::string>();

LuaRef value = e.value<LuaRef>();

…

}

你也可以和Lua 原生API 混用

lua_State *L = ...;
LuaRef v = ...;
lua_getglobal(L, "my_method");
Lua::push(L, 1);                    // the same as lua_pushinteger
Lua::push(L, v);                    // push v to lua stack
Lua::push(L, true);                 // the same as lua_pushboolean
lua_call(L, 3, 2);
LuaRef r(L, -2);                    // map r to lua stack index -2

C++ 调用Lua 脚本

下面实际的实现一个例子展示如何使用C++ 调用Lua 脚本，将代码运行起来更直观！

编写call_lua.cpp 的代码如下

#define LUAINTF_LINK_LUA_COMPILED_IN_CXX 0
#include "LuaIntf/LuaIntf.h"

#include <lua.hpp>
#include <string>
#include <iostream>

using namespace std;
struct lua_State;
int main()

{

using LuaRef = LuaIntf::LuaRef;
<span class="k">try</span> <span class="p">{</span>
    <span class="n">lua_State</span> <span class="o">*</span><span class="n">L</span> <span class="o">=</span> <span class="n">luaL_newstate</span><span class="p">();</span>
    <span class="n">luaL_openlibs</span><span class="p">(</span><span class="n">L</span><span class="p">);</span>

    <span class="n">LuaIntf</span><span class="o">::</span><span class="n">LuaContext</span> <span class="n">ctx</span><span class="p">(</span><span class="n">L</span><span class="p">);</span>
    <span class="n">ctx</span><span class="p">.</span><span class="n">doFile</span><span class="p">(</span><span class="s">&#34;./test_ref.lua&#34;</span><span class="p">);</span>

    <span class="n">LuaRef</span> <span class="n">func</span><span class="p">(</span><span class="n">L</span><span class="p">,</span> <span class="s">&#34;test_module.test_func&#34;</span><span class="p">);</span>
    <span class="n">func</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="nb">true</span><span class="p">,</span> <span class="s">&#34;hello world&#34;</span><span class="p">);</span>
<span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="k">const</span> <span class="n">LuaIntf</span><span class="o">::</span><span class="n">LuaException</span> <span class="o">&amp;</span><span class="n">e</span><span class="p">)</span> <span class="p">{</span>
    <span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&#34;Error: &#34;</span> <span class="o">&lt;&lt;</span> <span class="n">e</span><span class="p">.</span><span class="n">what</span><span class="p">()</span> <span class="o">&lt;&lt;</span> <span class="n">endl</span><span class="p">;</span>
<span class="p">}</span>

<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>

}

在编写对应的test_ref.lua 代码如下

local M = {}
local modelName = "test_module"
_G[modelName] = M
function M.test_func(int_v, bool_v, string_v)

print<span class="