1、Lua和C++交互

1、lua和c++交互機(jī)制是基于一個(gè)虛擬棧，C++和lua之間的所有數(shù)據(jù)交互都通過(guò)這個(gè)虛擬棧來(lái)完成，無(wú)論何時(shí)C++想從lua中調(diào)用一個(gè)值，被請(qǐng)求的值將會(huì)被壓入棧，C++想要傳遞一個(gè)值給Lua，首選將整個(gè)值壓棧，然后就可以在Lua中調(diào)用。
2、lua中提供正向和反向索引，區(qū)別在于證書(shū)永遠(yuǎn)是棧底，負(fù)數(shù)永遠(yuǎn)是棧頂。

2、基礎(chǔ)練習(xí)

編譯指令：g++ test.cpp -o test -llua -ldl

#include <iostream>  
#include <string.h>  
using namespace std;
 
extern "C"
{
#include "lua.h"  
#include "lauxlib.h"  
#include "lualib.h"  
}

// g++ test.cpp -o test  -llua -ldl
int main()
{
	//1.創(chuàng)建一個(gè)state  
	// luaL_newstate返回一個(gè)指向堆棧的指針
	lua_State *L = luaL_newstate();
 
	//2.入棧操作  
	lua_pushstring(L, "hello world");
	lua_pushnumber(L, 200);
 
	//3.取值操作  
	if (lua_isstring(L, 1)) {             //判斷是否可以轉(zhuǎn)為string  
		cout << lua_tostring(L, 1) << endl;  //轉(zhuǎn)為string并返回  
	}
	if (lua_isnumber(L, 2)) {
		cout << lua_tonumber(L, 2) << endl;
	}
 
	//4.關(guān)閉state  
	lua_close(L);
	return 0;
}

2.1、加載Lua腳本并傳遞參數(shù)

編譯指令：g++ test.cpp -o test -llua -ldl

函數(shù)說(shuō)明：

1、函數(shù)用于將Lua腳本加載到Lua虛擬機(jī)中并進(jìn)行編譯
luaL_loadbuffer(L,s,sz,n)
	lua_State *L：Lua狀態(tài)對(duì)象，表示Lua虛擬機(jī)的運(yùn)行實(shí)例。
	const char *buff：指向Lua腳本內(nèi)容的字符串。
	size_t sz：Lua腳本內(nèi)容的長(zhǎng)度。
	const char *name：可選參數(shù)，用于給腳本設(shè)置一個(gè)名稱(chēng)，便于調(diào)試和錯(cuò)誤消息的輸出。
	返回值：
		不為0表示有錯(cuò)誤

2、函數(shù)用于調(diào)用Lua函數(shù)并處理其執(zhí)行過(guò)程中可能發(fā)生的錯(cuò)誤
lua_pcall(L,n,r,f)
	lua_State *L：Lua狀態(tài)對(duì)象，表示Lua虛擬機(jī)的運(yùn)行實(shí)例。
	int nargs：傳遞給Lua函數(shù)的參數(shù)數(shù)量。
	int nresults：期望的返回值數(shù)量。
	int errfunc：錯(cuò)誤處理函數(shù)在調(diào)用棧中的索引。
	返回值：
		不為0表示有錯(cuò)誤

3、函數(shù)用于從全局環(huán)境中獲取一個(gè)全局變量，并將其值壓入Lua棧頂
int lua_getglobal(lua_State *L, const char *name)
	lua_State *L：Lua狀態(tài)對(duì)象，表示Lua虛擬機(jī)的運(yùn)行實(shí)例。
	const char *name：要獲取的全局變量的名稱(chēng)。

4、函數(shù)用于將一個(gè)數(shù)字（lua_Number類(lèi)型）壓入Lua棧頂
void lua_pushnumber(lua_State *L, lua_Number n)
	lua_State *L：Lua狀態(tài)對(duì)象，表示Lua虛擬機(jī)的運(yùn)行實(shí)例。
	lua_Number n：要壓入棧的數(shù)字。

執(zhí)行流程：
1、加載script腳本加載到lua虛擬機(jī)中
2、將腳本中的my_pow函數(shù)，壓入到棧頂
3、壓入my_pow需要的兩個(gè)參數(shù)
4、執(zhí)行腳本
5、獲取腳本中的返回值

#include <cstdio>
#include <cstring>
#include <cmath>
#include <new>
extern "C" {
    #include <lua.h>
    #include <lualib.h>
    #include <lauxlib.h>
}

char const *script = R"(
function hello()
    print('hello world')
end

function my_pow(x,y)
    return x^y
end
)";

char const *script_1 = R"(
    pkg.hello()
)";

int main()
{
    /*
        加載腳本并傳遞參數(shù)
    */
    
    // 創(chuàng)建lua虛擬機(jī)，創(chuàng)建虛擬棧
    lua_State *state = luaL_newstate();
    // 打開(kāi)lua標(biāo)準(zhǔn)庫(kù)，以便正常使用lua api
    luaL_openlibs(state);
    {
        // 將lua腳本加載到虛擬機(jī)中，并編譯
        auto rst = luaL_loadbuffer(state,script,strlen(script),"hello");
        // 判斷是否加載成功
        if(rst !=0 ){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script faile:%s\n",msg);
                lua_pop(state,-1);
            }
            return -1;
        }
        // 執(zhí)行加載并編譯的Lua腳本
        if(lua_pcall(state,0,0,0)){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script faile:%s",msg);
                lua_pop(state,-1);
            }
        }

        // 從全局環(huán)境中獲取一個(gè)my_pow函數(shù)壓入到棧頂
        lua_getglobal(state,"my_pow");
        // 判斷棧頂是不是一個(gè)函數(shù)，要是不是表示沒(méi)有找到
        if(!lua_isfunction(state,-1)){
            printf("function  named my_pow not function\n");
            return -1;
        }
        // 將數(shù)字參數(shù)壓入Lua棧中
        lua_pushnumber(state,2);
        lua_pushnumber(state,8);
        rst = lua_pcall(state,2,1,0);
        if(rst !=0 ){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script faile:%s\n",msg);
                lua_pop(state,-1);
            }
            return -1;
        }
        if(lua_isnumber(state,-1)){
            lua_Number val = lua_tonumber(state,-1);
            printf("%lf\n",val);
        }
    }
    lua_close(state);
    return 0;
}

2.2、加載腳本到stable（包）

編譯命令： g++ main.cpp -o main -llua -ldl文章來(lái)源地址http://www.zghlxwxcb.cn/news/detail-714985.html

#include <cstdio>
#include <cstring>
#include <cmath>
#include <new>
extern "C" {
    #include <lua.h>
    #include <lualib.h>
    #include <lauxlib.h>
}
char const *script = R"(
function hello()
    print('hello world')
end

function my_pow(x,y)
    return x^y
end
)";

/*   
	_G = {
    "helloworld" = function print("hello world")
    }
    _G = {
        "pkg" = {
            "helloworld" = function print("hello world")
        }
    }

    pkg.helloworld()
*/
    
char const *script_1 = R"(
    pkg.hello()
)";

int main()
{
    /*
        加載腳本到stable（包）
        1、生成chunk push到棧頂
        2、創(chuàng)建table，設(shè)置給_G表，_G["pkg"] = {}
        3、給這個(gè)table設(shè)置元表，元表繼承_G的訪(fǎng)問(wèn)域(__index)
        4、執(zhí)行code chunk
    */
    lua_State *state = luaL_newstate();
    luaL_openlibs(state);
    {
        auto rst = luaL_loadbuffer(state,script,strlen(script),"helloworld");
        if(rst != 0){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script faile:%s\n",msg);
                lua_pop(state,1);
            }
            return -1;
        }
        
        // 取出_G表
        lua_getglobal(state,"_G");
        if(lua_istable(state,-1)){  // chunk _G
            lua_newtable(state);    // 創(chuàng)建表 chunk _G new_stable
            lua_pushstring(state,"pkg"); // chunk _G new_stable pkg
            lua_pushvalue(state,-2); // chunk _G new_stable pkg new_stable
            lua_rawset(state,-4);   // chunk _G new_stable
            char const *upvalueName = lua_setupvalue(state,-3,1); // chunk _G
            lua_newtable(state);    // chunk _G metastable
            lua_pushstring(state,"__index");    // chunk _G metastable "__index"
            lua_pushvalue(state,-3); // chunk _G metastable "__index" _G
            lua_rawset(state,-3);   // chunk _G metastable
            lua_pushstring(state,"pkg");
            lua_rawget(state,-3);   // chunk _G metastable "pkg"(table)
            lua_pushvalue(state,-2);    // chunk _G metastable pkg(table) metastable
            lua_setmetatable(state,-2); // chunk _G metastable pkg(stable)
            lua_pop(state,3);   // chunk
        }
        // 執(zhí)行chunk
        if(lua_pcall(state,0,0,0)){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("call function chunk failed:%s\n",msg);
                lua_pop(state,1);
            }
        }

        // 加載script_1
        rst = luaL_loadbuffer(state,script_1,strlen(script_1),"script_1");
        if(rst != 0){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script failed:%s\n",msg);
                lua_pop(state,1);
            }
            return -1;
        }

        if(lua_pcall(state,0,0,0)){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("call function chunk failed:%s\n",msg);
                lua_pop(state,1);
            }
        }
        lua_close(state);
    }
    return 0;
}

2.3、Lua調(diào)用c語(yǔ)言接口

#include <cstdio>
#include <cstring>
#include <cmath>
#include <new>
extern "C" {
    #include <lua.h>
    #include <lualib.h>
    #include <lauxlib.h>
}

int pow_from_c(lua_State *L)
{
    int param_count = lua_gettop(L);
    if(param_count != 2)
        return 0;
    
    if(lua_isinteger(L,1) && lua_isinteger(L,2)){
        auto x = lua_tointeger(L,1);
        auto y = lua_tointeger(L,2);
        int rst = (int)pow(x,y);
        lua_pushinteger(L,rst);
        return 1;
    }
    return 0;
}

char const *script_2 = R"(
    local val = pow_from_c(2,3)
    print(val)
)";
int main()
{
    // lua調(diào)用c語(yǔ)言接口
    lua_State *state = luaL_newstate();
    luaL_openlibs(state);
    {
        /*
            "_G" = {
                "pow_from_c" = pow_from_c
            }
        */
        lua_getglobal(state,"_G");
        lua_pushstring(state,"pow_from_c");
        lua_pushcclosure(state,pow_from_c,0);    // _G "pow_from_c"; closure
        lua_rawset(state,-3);   // _G
        lua_pop(state,1);   // _G
    }

    auto rst = luaL_loadbuffer(state,script_2,strlen(script_2),"script_2");
    if(rst != 0){
        if(lua_isstring(state,-1)){
            auto msg = lua_tostring(state,-1);
            printf("load script faile:%s\n",msg);
            lua_pop(state,1);
        }
        return -1;
    }

    if(lua_pcall(state,0,0,0)){
        if(lua_isstring(state,-1)){
            auto msg = lua_tostring(state,-1);
            printf("call function chunk failed:%s\n",msg);
            lua_pop(state,1);
        }
    }
    lua_close(state);
    return 0;
}

2.4、Lua實(shí)現(xiàn)面向?qū)ο?/h3>

local anial_matestable = {
    __index = {
        walk = function (self)
            print(self,"我是walk")
        end,
        eat = function (self)
            print(self,"eat.")
        end,
    },

    __newindex = function (object,key,value)
        print("assigned "..value.."named "..key.."but not really")
    end,
}

function newobject()
    local objs = {name = "xxxx"}
    setmetatable(objs,anial_matestable)
    return objs
end

local obj = newobject()
obj.eat()
obj.walk()
obj.name = "abc"
obj.id = 0

2.5、向腳本中注冊(cè)c++的類(lèi)

#include <cstdio>
#include <cstring>
#include <cmath>
#include <new>
extern "C" {
    #include <lua.h>
    #include <lualib.h>
    #include <lauxlib.h>
}
char const *script_3 = R"(
    local obj_1 = create_game_object(1);
    local obj_2 = create_game_object(1);
    local obj_3 = create_game_object(2);
    local rst1 = obj_1:equal(obj_2)
    local rst2 = obj_1:equal(obj_3)
    print(rst1,";",rst2)
    print(""..obj_1:id())
)";

class GameObject{
private:
    u_int32_t _id;
public:
    static size_t registy_value;
public:
    GameObject(u_int32_t id):_id(id)
    {}
    u_int32_t id()const{
        return _id;
    }
    bool equal(GameObject *obj){
        return _id == obj->id();
    }
};
size_t GameObject::registy_value = 0;

int GameObject_equal(lua_State *state){
    int arg_count = lua_gettop(state);
    if(arg_count!=2){
        return 0;
    }

    if(lua_isuserdata(state,1) && lua_isuserdata(state,2)){
        void *userdata_self = lua_touserdata(state,1);
        void *userdata_that = lua_touserdata(state,2);
        GameObject *obj1 = (GameObject*)userdata_self;
        GameObject *obj2 = (GameObject*)userdata_that;
        auto rst = obj1->equal(obj2);
        lua_pushboolean(state,rst);
        return 1;
    }
    return 0;
}

int GameObject_id(lua_State* state){
    GameObject *this_obj = (GameObject*)lua_touserdata(state,1);
    auto rst = this_obj->id();
    lua_pushinteger(state,rst);
    return 1;
}

int create_game_object(lua_State* state){
    auto id = lua_tointeger(state,1);
    void *p = lua_newuserdata(state,sizeof(GameObject));
    GameObject *obj = new(p)GameObject(id);
    lua_rawgetp(state,LUA_REGISTRYINDEX,&GameObject::registy_value);
    lua_setmetatable(state,-2);
    return 1;
}

int main()
{
    // 怎么向腳本中注冊(cè)c++的類(lèi)
    // 使用userdata
    /*
        userdata:{
            metadata:{
                __index = {
                    equal = function(){},
                    id = function(){},
                }
            }
        }
    */
    lua_State *state = luaL_newstate();
    luaL_openlibs(state);
    {
        lua_getglobal(state,"_G");
        lua_pushstring(state,"create_game_object");
        lua_pushcclosure(state,create_game_object,0);
        lua_rawset(state,-3);
        lua_pop(state,1);

        lua_newtable(state);
        lua_pushstring(state,"__index");
        lua_newtable(state);
        lua_pushstring(state,"equal");
        lua_pushcclosure(state,GameObject_equal,0);
        lua_rawset(state,-3);
        lua_pushstring(state,"id");
        lua_pushcclosure(state,GameObject_id,0);
        lua_rawset(state,-3);
        lua_rawset(state,-3);

        lua_rawsetp(state,LUA_REGISTRYINDEX,&GameObject::registy_value);
        auto rst = luaL_loadbuffer(state,script_3,strlen(script_3),"oop");
        if(rst != 0){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script failed:%s\n",msg);
                lua_pop(state,1);
            }
            return -1;
        }
        // 執(zhí)行
        if(lua_pcall(state,0,0,0)){
            if(lua_isstring(state,-1)){
                auto msg = lua_tostring(state,-1);
                printf("load script failed:%s\n",msg);
                lua_pop(state,1);
            }
        }
    }
    lua_close(state);
    return 0;
}

到了這里，關(guān)于Lua與C++交互的文章就介紹完了。如果您還想了解更多內(nèi)容，請(qǐng)?jiān)谟疑辖撬阉鱐OY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！