使用 Lunar 进行 Cpp 绑定
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使用 Lunar 进行 Cpp 绑定 |
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这是 Luna 的改进版本（参见 SimplerCppBinding），它允许您从 C++ 应用程序调用 Lua 方法。
您也可以在 Lua 脚本或 C++ 应用程序中创建对象。在 Lua 中创建的对象将由 userdata 的 gc 事件删除。您可以指定在 C++ 应用程序中创建的对象是否由 userdata 的 gc 事件删除。
lunar.h 有两个额外的公共方法：push 和 call。
push 接收指向对象的指针，并将一个唯一的 [1] userdata 推送到堆栈上，并返回此 userdata 的堆栈索引。可选的第二个参数指定在 userdata 的 gc 事件发生时是否删除对象。此参数的默认值为 false，这意味着不会删除对象。
call 只是 lua_pcall 的包装器。在调用 call 之前，将 userdata 和参数推送到堆栈上。然后，它将从 userdata 中检索命名方法，并使用 lua_pcall 调用此函数。call 将返回堆栈上的结果数量，或者如果发生错误则返回负数。任何错误消息都将保留在堆栈顶部。
CallingLuaFromCpp 展示了如何使用这些额外功能。
extern "C" {
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
}
#include "lunar.h"
class Account {
lua_Number m_balance;
public:
static const char className[];
static Lunar<Account>::RegType methods[];
Account(lua_State *L) { m_balance = luaL_checknumber(L, 1); }
int deposit (lua_State *L) { m_balance += luaL_checknumber(L, 1); return 0; }
int withdraw(lua_State *L) { m_balance -= luaL_checknumber(L, 1); return 0; }
int balance (lua_State *L) { lua_pushnumber(L, m_balance); return 1; }
~Account() { printf("deleted Account (%p)\n", this); }
};
const char Account::className[] = "Account";
Lunar<Account>::RegType Account::methods[] = {
LUNAR_DECLARE_METHOD(Account, deposit),
LUNAR_DECLARE_METHOD(Account, withdraw),
LUNAR_DECLARE_METHOD(Account, balance),
{0,0}
};
int main(int argc, char *argv[])
{
lua_State *L = lua_open();
luaL_openlibs(L);
Lunar<Account>::Register(L);
if(argc>1) luaL_dofile(L, argv[1]);
lua_gc(L, LUA_GCCOLLECT, 0); // collected garbage
lua_close(L);
return 0;
}
extern "C" {
#include "lua.h"
#include "lauxlib.h"
}
template <typename T> class Lunar {
typedef struct { T *pT; } userdataType;
public:
typedef int (T::*mfp)(lua_State *L);
typedef struct { const char *name; mfp mfunc; } RegType;
static void Register(lua_State *L) {
lua_newtable(L);
int methods = lua_gettop(L);
luaL_newmetatable(L, T::className);
int metatable = lua_gettop(L);
// store method table in globals so that
// scripts can add functions written in Lua.
lua_pushvalue(L, methods);
set(L, LUA_GLOBALSINDEX, T::className);
// hide metatable from Lua getmetatable()
lua_pushvalue(L, methods);
set(L, metatable, "__metatable");
lua_pushvalue(L, methods);
set(L, metatable, "__index");
lua_pushcfunction(L, tostring_T);
set(L, metatable, "__tostring");
lua_pushcfunction(L, gc_T);
set(L, metatable, "__gc");
lua_newtable(L); // mt for method table
lua_pushcfunction(L, new_T);
lua_pushvalue(L, -1); // dup new_T function
set(L, methods, "new"); // add new_T to method table
set(L, -3, "__call"); // mt.__call = new_T
lua_setmetatable(L, methods);
// fill method table with methods from class T
for (RegType *l = T::methods; l->name; l++) {
lua_pushstring(L, l->name);
lua_pushlightuserdata(L, (void*)l);
lua_pushcclosure(L, thunk, 1);
lua_settable(L, methods);
}
lua_pop(L, 2); // drop metatable and method table
}
// call named lua method from userdata method table
static int call(lua_State *L, const char *method,
int nargs=0, int nresults=LUA_MULTRET, int errfunc=0)
{
int base = lua_gettop(L) - nargs; // userdata index
if (!luaL_checkudata(L, base, T::className)) {
lua_settop(L, base-1); // drop userdata and args
lua_pushfstring(L, "not a valid %s userdata", T::className);
return -1;
}
lua_pushstring(L, method); // method name
lua_gettable(L, base); // get method from userdata
if (lua_isnil(L, -1)) { // no method?
lua_settop(L, base-1); // drop userdata and args
lua_pushfstring(L, "%s missing method '%s'", T::className, method);
return -1;
}
lua_insert(L, base); // put method under userdata, args
int status = lua_pcall(L, 1+nargs, nresults, errfunc); // call method
if (status) {
const char *msg = lua_tostring(L, -1);
if (msg == NULL) msg = "(error with no message)";
lua_pushfstring(L, "%s:%s status = %d\n%s",
T::className, method, status, msg);
lua_remove(L, base); // remove old message
return -1;
}
return lua_gettop(L) - base + 1; // number of results
}
// push onto the Lua stack a userdata containing a pointer to T object
static int push(lua_State *L, T *obj, bool gc=false) {
if (!obj) { lua_pushnil(L); return 0; }
luaL_getmetatable(L, T::className); // lookup metatable in Lua registry
if (lua_isnil(L, -1)) luaL_error(L, "%s missing metatable", T::className);
int mt = lua_gettop(L);
subtable(L, mt, "userdata", "v");
userdataType *ud =
static_cast<userdataType*>(pushuserdata(L, obj, sizeof(userdataType)));
if (ud) {
ud->pT = obj; // store pointer to object in userdata
lua_pushvalue(L, mt);
lua_setmetatable(L, -2);
if (gc == false) {
lua_checkstack(L, 3);
subtable(L, mt, "do not trash", "k");
lua_pushvalue(L, -2);
lua_pushboolean(L, 1);
lua_settable(L, -3);
lua_pop(L, 1);
}
}
lua_replace(L, mt);
lua_settop(L, mt);
return mt; // index of userdata containing pointer to T object
}
// get userdata from Lua stack and return pointer to T object
static T *check(lua_State *L, int narg) {
userdataType *ud =
static_cast<userdataType*>(luaL_checkudata(L, narg, T::className));
if(!ud) {
luaL_typerror(L, narg, T::className);
return NULL;
}
return ud->pT; // pointer to T object
}
private:
Lunar(); // hide default constructor
// member function dispatcher
static int thunk(lua_State *L) {
// stack has userdata, followed by method args
T *obj = check(L, 1); // get 'self', or if you prefer, 'this'
lua_remove(L, 1); // remove self so member function args start at index 1
// get member function from upvalue
RegType *l = static_cast<RegType*>(lua_touserdata(L, lua_upvalueindex(1)));
return (obj->*(l->mfunc))(L); // call member function
}
// create a new T object and
// push onto the Lua stack a userdata containing a pointer to T object
static int new_T(lua_State *L) {
lua_remove(L, 1); // use classname:new(), instead of classname.new()
T *obj = new T(L); // call constructor for T objects
push(L, obj, true); // gc_T will delete this object
return 1; // userdata containing pointer to T object
}
// garbage collection metamethod
static int gc_T(lua_State *L) {
if (luaL_getmetafield(L, 1, "do not trash")) {
lua_pushvalue(L, 1); // dup userdata
lua_gettable(L, -2);
if (!lua_isnil(L, -1)) return 0; // do not delete object
}
userdataType *ud = static_cast<userdataType*>(lua_touserdata(L, 1));
T *obj = ud->pT;
if (obj) delete obj; // call destructor for T objects
return 0;
}
static int tostring_T (lua_State *L) {
char buff[32];
userdataType *ud = static_cast<userdataType*>(lua_touserdata(L, 1));
T *obj = ud->pT;
sprintf(buff, "%p", (void*)obj);
lua_pushfstring(L, "%s (%s)", T::className, buff);
return 1;
}
static void set(lua_State *L, int table_index, const char *key) {
lua_pushstring(L, key);
lua_insert(L, -2); // swap value and key
lua_settable(L, table_index);
}
static void weaktable(lua_State *L, const char *mode) {
lua_newtable(L);
lua_pushvalue(L, -1); // table is its own metatable
lua_setmetatable(L, -2);
lua_pushliteral(L, "__mode");
lua_pushstring(L, mode);
lua_settable(L, -3); // metatable.__mode = mode
}
static void subtable(lua_State *L, int tindex, const char *name, const char *mode) {
lua_pushstring(L, name);
lua_gettable(L, tindex);
if (lua_isnil(L, -1)) {
lua_pop(L, 1);
lua_checkstack(L, 3);
weaktable(L, mode);
lua_pushstring(L, name);
lua_pushvalue(L, -2);
lua_settable(L, tindex);
}
}
static void *pushuserdata(lua_State *L, void *key, size_t sz) {
void *ud = 0;
lua_pushlightuserdata(L, key);
lua_gettable(L, -2); // lookup[key]
if (lua_isnil(L, -1)) {
lua_pop(L, 1); // drop nil
lua_checkstack(L, 3);
ud = lua_newuserdata(L, sz); // create new userdata
lua_pushlightuserdata(L, key);
lua_pushvalue(L, -2); // dup userdata
lua_settable(L, -4); // lookup[key] = userdata
}
return ud;
}
};
#define LUNAR_DECLARE_METHOD(Class, Name) {#Name, &Class::Name}
此代码可以为 Lua 5.0 编译如下
g++ -o test account.cc -L/usr/local/lib -llua -llualib
function printf(...) io.write(string.format(unpack(arg))) end function Account:show() printf("Account balance = $%0.02f\n", self:balance()) end a = Account(100) b = Account:new(30) print('a =', a) print('b =', b) print('metatable =', getmetatable(a)) print('Account =', Account) table.foreach(Account, print) a:show() a:deposit(50.30) a:show() a:withdraw(25.10) a:show() parent = {} function parent:rob(amount) amount = amount or self:balance() self:withdraw(amount) return amount end getmetatable(Account).__index = parent debug.debug()
$ ./test account.lua a = Account (0xa041d98) b = Account (0xa045390) metatable = table: 0xa044f28 Account = table: 0xa044f28 show function: 0xa046760 balance function: 0xa0455f8 withdraw function: 0xa045300 deposit function: 0xa045508 new function: 0xa044fe8 Account balance = $100.00 Account balance = $150.30 Account balance = $125.20 lua_debug> a:show() Account balance = $125.20 lua_debug> b:show() Account balance = $30.00 lua_debug> print(a:rob(20)) 20 lua_debug> a:show() Account balance = $105.20 lua_debug> b:deposit(a:rob()) lua_debug> a:show() Account balance = $0.00 lua_debug> b:show() Account balance = $135.20 lua_debug> cont deleted Account (0xa045390) deleted Account (0xa041d98)