本篇主题是C#如何调用lua的补充。
xLua交互知识
参考官方文档《programming in lua》的第24章开头，里面很详细地阐述了Lua和C++是如何实现交互的：栈操作。Lua API用一个抽象的栈在Lua与C之间交换值。栈中的每一条记录都可以保存任何 Lua 值。如果想要从Lua请求一个值（比如一个全局变量的值）则调用Lua，被请求的值将会被压入栈；如果想要传递一个值给 Lua，首先将这个值压入栈，然后调用 Lua（这个值就会被弹 出）。几乎所有的 API函数都用到了栈。而C#显而易见也可以和C++一侧进行交互，由此即可得出lua和C#可以通过C/C++这一层来进行通信，主要方法即是lua的堆栈操作。
C#获取Lua入口
首先写一段测试代码：
cs
[LuaCallCSharp]
public class LuaTableTest
{
public LuaTable tab = null;
public Action<LuaTable> luaFunc = null;
}然后经过Xlua Generate Code后可以观察Set方法，得到流程的起点：translator.GetObject
cs
[MonoPInvokeCallbackAttribute(typeof(LuaCSFunction))]
static int _s_set_tab(RealStatePtr L)
{
try {
ObjectTranslator translator = ObjectTranslatorPool.Instance.Find(L);
XluaTool.LuaTableTest gen_to_be_invoked = (XluaTool.LuaTableTest)translator.FastGetCSObj(L, 1);
gen_to_be_invoked.tab = (XLua.LuaTable)translator.GetObject(L, 2, typeof(XLua.LuaTable));
} catch(System.Exception gen_e) {
return LuaAPI.luaL_error(L, "c# exception:" + gen_e);
}
return 0;
}
[MonoPInvokeCallbackAttribute(typeof(LuaCSFunction))]
static int _s_set_luaFunc(RealStatePtr L)
{
try {
ObjectTranslator translator = ObjectTranslatorPool.Instance.Find(L);
XluaTool.LuaTableTest gen_to_be_invoked = (XluaTool.LuaTableTest)translator.FastGetCSObj(L, 1);
gen_to_be_invoked.luaFunc = translator.GetDelegate<System.Action<XLua.LuaTable>>(L, 2);
} catch(System.Exception gen_e) {
return LuaAPI.luaL_error(L, "c# exception:" + gen_e);
}
return 0;
}可以看到，translator.GetObject负责把相应Lua类型转换成C#类型数据并返回。而GetObject内部是由GetCaster函数实现转换的：
cs
public ObjectCast GetCaster(Type type)
{
if (type.IsByRef) type = type.GetElementType();
Type underlyingType = Nullable.GetUnderlyingType(type);
if (underlyingType != null)
{
return genNullableCaster(GetCaster(underlyingType));
}
ObjectCast oc;
if (!castersMap.TryGetValue(type, out oc))
{
oc = genCaster(type);
castersMap.Add(type, oc);
}
return oc;
}castersMap内部已经定义了各个类型的转换函数：
cs
public ObjectCasters(ObjectTranslator translator)
{
this.translator = translator;
castersMap[typeof(char)] = charCaster;
castersMap[typeof(sbyte)] = sbyteCaster;
castersMap[typeof(byte)] = byteCaster;
castersMap[typeof(short)] = shortCaster;
castersMap[typeof(ushort)] = ushortCaster;
castersMap[typeof(int)] = intCaster;
castersMap[typeof(uint)] = uintCaster;
castersMap[typeof(long)] = longCaster;
castersMap[typeof(ulong)] = ulongCaster;
castersMap[typeof(double)] = getDouble;
castersMap[typeof(float)] = floatCaster;
castersMap[typeof(decimal)] = decimalCaster;
castersMap[typeof(bool)] = getBoolean;
castersMap[typeof(string)] = getString;
castersMap[typeof(object)] = getObject;
castersMap[typeof(byte[])] = getBytes;
castersMap[typeof(IntPtr)] = getIntptr;
//special type
castersMap[typeof(LuaTable)] = getLuaTable;
castersMap[typeof(LuaFunction)] = getLuaFunction;
}所以接下来的任务无非就是研究getLuaTable和getLuaFunction如何实现的了。
C#获取Lua table
getLuaFunction实现如下：
cs
private object getLuaTable(RealStatePtr L, int idx, object target)
{
if (LuaAPI.lua_type(L, idx) == LuaTypes.LUA_TUSERDATA)
{
object obj = translator.SafeGetCSObj(L, idx);
return (obj != null && obj is LuaTable) ? obj : null;
}
if (!LuaAPI.lua_istable(L, idx))
{
return null;
}
LuaAPI.lua_pushvalue(L, idx);
return new LuaTable(LuaAPI.luaL_ref(L), translator.luaEnv);
}主要步骤即是通过luaL_ref添加到Lua注册表中并获取索引位置，创建一个C#侧的LuaTable对象用于管理。之后获取这个table即可直接用这个LuaTable对象即可。
如果使用测试代码
cs
LuaTableTest.tab.Get<int>("testVal")来获取相应变量信息，实际上内部执行的是table.Get接口：
cs
public void Get<TKey, TValue>(TKey key, out TValue value)
{
#if THREAD_SAFE || HOTFIX_ENABLE
lock (luaEnv.luaEnvLock)
{
#endif
var L = luaEnv.L;
var translator = luaEnv.translator;
int oldTop = LuaAPI.lua_gettop(L);
LuaAPI.lua_getref(L, luaReference);
translator.PushByType(L, key);
if (0 != LuaAPI.xlua_pgettable(L, -2))
{
string err = LuaAPI.lua_tostring(L, -1);
LuaAPI.lua_settop(L, oldTop);
throw new Exception("get field [" + key + "] error:" + err);
}
LuaTypes lua_type = LuaAPI.lua_type(L, -1);
Type type_of_value = typeof(TValue);
if (lua_type == LuaTypes.LUA_TNIL && type_of_value.IsValueType())
{
throw new InvalidCastException("can not assign nil to " + type_of_value.GetFriendlyName());
}
try
{
translator.Get(L, -1, out value);
}
catch (Exception e)
{
throw e;
}
finally
{
LuaAPI.lua_settop(L, oldTop);
}
#if THREAD_SAFE || HOTFIX_ENABLE
}
#endif
}可以看到，我们首先通过getref（之前new luaTable的时候已经做了添加ref的操作了）拿到table的reference，然后再通过这个reference查询到key的位置并取出，即可得到相应的数据了。
根据LuaTable获取变量
在Get代码中有一处细节：translator.Get，内部有提前封装好的基本类型对象转换，比如int、double、string类型等，这些都可以直接通过Lua API实现转换，LuaAPI.xlua_tointeger这些也仅仅是对原生API的简单封装。
cs
public void Get<T>(RealStatePtr L, int index, out T v)
{
Func<RealStatePtr, int, T> get_func;
if (tryGetGetFuncByType(typeof(T), out get_func))
{
v = get_func(L, index);
}
else
{
v = (T)GetObject(L, index, typeof(T));
}
}
cs
bool tryGetGetFuncByType<T>(Type type, out T func) where T : class
{
if (get_func_with_type == null)
{
get_func_with_type = new Dictionary<Type, Delegate>()
{
{typeof(int), new Func<RealStatePtr, int, int>(LuaAPI.xlua_tointeger) },
{typeof(double), new Func<RealStatePtr, int, double>(LuaAPI.lua_tonumber) },
{typeof(string), new Func<RealStatePtr, int, string>(LuaAPI.lua_tostring) },
{typeof(byte[]), new Func<RealStatePtr, int, byte[]>(LuaAPI.lua_tobytes) },
{typeof(bool), new Func<RealStatePtr, int, bool>(LuaAPI.lua_toboolean) },
{typeof(long), new Func<RealStatePtr, int, long>(LuaAPI.lua_toint64) },
{typeof(ulong), new Func<RealStatePtr, int, ulong>(LuaAPI.lua_touint64) },
{typeof(IntPtr), new Func<RealStatePtr, int, IntPtr>(LuaAPI.lua_touserdata) },
{typeof(decimal), new Func<RealStatePtr, int, decimal>((L, idx) => {
decimal ret;
Get(L, idx, out ret);
return ret;
}) },
{typeof(byte), new Func<RealStatePtr, int, byte>((L, idx) => (byte)LuaAPI.xlua_tointeger(L, idx) ) },
{typeof(sbyte), new Func<RealStatePtr, int, sbyte>((L, idx) => (sbyte)LuaAPI.xlua_tointeger(L, idx) ) },
{typeof(char), new Func<RealStatePtr, int, char>((L, idx) => (char)LuaAPI.xlua_tointeger(L, idx) ) },
{typeof(short), new Func<RealStatePtr, int, short>((L, idx) => (short)LuaAPI.xlua_tointeger(L, idx) ) },
{typeof(ushort), new Func<RealStatePtr, int, ushort>((L, idx) => (ushort)LuaAPI.xlua_tointeger(L, idx) ) },
{typeof(uint), new Func<RealStatePtr, int, uint>(LuaAPI.xlua_touint) },
{typeof(float), new Func<RealStatePtr, int, float>((L, idx) => (float)LuaAPI.lua_tonumber(L, idx) ) },
};
}
Delegate obj;
if (get_func_with_type.TryGetValue(type, out obj))
{
func = obj as T;
return true;
}
else
{
func = null;
return false;
}
}C#获取Function
以上已经说明，如果只是为了获取某个table内部的相关变量，其实走Get就已经满足需求，但是有些函数依然还需要调用，比如一些匿名函数：
Lua
XluaTool.LuaTableTest.luaFunc= function()
end此时需要转换成delegate形式供C#侧调用，如第二段代码块中所示：
cs
gen_to_be_invoked.luaFunc = translator.GetDelegate<System.Action<XLua.LuaTable>>(L, 2);而跳转GetDelegate直到CreateDelegateBridge函数，会发现其中有一些代码和GetLuaTable非常相似，即会存储在lua注册表中，然后给出一个索引，最后通过DelegateBridgeBase类进行存储：
cs
public object CreateDelegateBridge(RealStatePtr L, Type delegateType, int idx)
{
......
LuaAPI.lua_pushvalue(L, idx);
int reference = LuaAPI.luaL_ref(L);
LuaAPI.lua_pushvalue(L, idx);
LuaAPI.lua_pushnumber(L, reference);
LuaAPI.lua_rawset(L, LuaIndexes.LUA_REGISTRYINDEX);
DelegateBridgeBase bridge;
try
{
#if (UNITY_EDITOR || XLUA_GENERAL) && !NET_STANDARD_2_0
if (!DelegateBridge.Gen_Flag)
{
bridge = Activator.CreateInstance(delegate_birdge_type, new object[] { reference, luaEnv }) as DelegateBridgeBase;
}
else
#endif
{
bridge = new DelegateBridge(reference, luaEnv);
}
}
......
}LuaBase Dispose
C#这边释放lua侧资源时需要调用相关接口，以防Lua侧一直认为C#侧持有lua相关资源。可以着重观察Xlua给的LuaBase析构函数的处理方式：
cs
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
public virtual void Dispose(bool disposeManagedResources)
{
if (!disposed)
{
if (luaReference != 0)
{
#if THREAD_SAFE || HOTFIX_ENABLE
lock (luaEnv.luaEnvLock)
{
#endif
bool is_delegate = this is DelegateBridgeBase;
if (disposeManagedResources)
{
luaEnv.translator.ReleaseLuaBase(luaEnv.L, luaReference, is_delegate);
}
else //will dispse by LuaEnv.GC
{
luaEnv.equeueGCAction(new LuaEnv.GCAction { Reference = luaReference, IsDelegate = is_delegate });
}
#if THREAD_SAFE || HOTFIX_ENABLE
}
#endif
}
disposed = true;
}
}调用Dispose接口，里面通知了translator此luaBase需要被释放，而translator则开始对lua注册表进行pop工作，尤其不要忘记之前的reference存储工作，也是要进行解绑的，如最后一句LuaAPI.lua_unref操作：
cs
public void ReleaseLuaBase(RealStatePtr L, int reference, bool is_delegate)
{
if(is_delegate)
{
LuaAPI.xlua_rawgeti(L, LuaIndexes.LUA_REGISTRYINDEX, reference);
if (LuaAPI.lua_isnil(L, -1))
{
LuaAPI.lua_pop(L, 1);
}
else
{
LuaAPI.lua_pushvalue(L, -1);
LuaAPI.lua_rawget(L, LuaIndexes.LUA_REGISTRYINDEX);
if (LuaAPI.lua_type(L, -1) == LuaTypes.LUA_TNUMBER && LuaAPI.xlua_tointeger(L, -1) == reference) //
{
//UnityEngine.Debug.LogWarning("release delegate ref = " + luaReference);
LuaAPI.lua_pop(L, 1);// pop LUA_REGISTRYINDEX[func]
LuaAPI.lua_pushnil(L);
LuaAPI.lua_rawset(L, LuaIndexes.LUA_REGISTRYINDEX); // LUA_REGISTRYINDEX[func] = nil
}
else //another Delegate ref the function before the GC tick
{
LuaAPI.lua_pop(L, 2); // pop LUA_REGISTRYINDEX[func] & func
}
}
LuaAPI.lua_unref(L, reference);
delegate_bridges.Remove(reference);
}
else
{
LuaAPI.lua_unref(L, reference);
}
}