Allow associating a table with Lua-bound objects, for storing state in Lua.
Design goals are: minimal overhead (one table); minimal extra code to use it (two lines in the header, to have a space to store a reference to the table), same API for classes with and without a table; allow switching to a table-bound class without derived classes having to know about it; keep zero per-object overhead for classes that don't need it.
This commit is contained in:
Glenn Maynard
@@ -1,5 +1,6 @@
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#include "global.h"
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#include "LuaBinding.h"
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#include "RageUtil.h"
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void CreateMethodsTable( lua_State *L, const CString &szName )
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{
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@@ -63,6 +64,196 @@ bool CheckLuaObjectType( lua_State *L, int narg, const char *szType )
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}
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}
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bool GetGlobalTable( Lua *L, bool bCreate )
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{
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lua_pushstring( L, "userdatas" );
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lua_rawget( L, LUA_REGISTRYINDEX );
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if( !lua_isnil(L, -1) )
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return true;
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lua_pop( L, 1 );
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if( !bCreate )
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return false;
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/* Save it. */
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lua_newtable( L );
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lua_pushstring( L, "userdatas" );
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lua_pushvalue( L, -2 );
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lua_rawset( L, LUA_REGISTRYINDEX );
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return true;
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}
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/* The object is on the stack. It's either a table or a userdata.
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* If needed, associate the metatable; if a table, also add it to
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* the userdata table. */
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void ApplyDerivedType( Lua *L, const CString &sClassName, void *pSelf )
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{
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int iTable = lua_gettop( L );
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int iType = lua_type( L, iTable );
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ASSERT_M( iType == LUA_TTABLE || iType == LUA_TUSERDATA,
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ssprintf("%i", iType) );
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if( iType == LUA_TTABLE )
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{
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GetGlobalTable( L, true );
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int iGlobalTable = lua_gettop( L );
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/* If the table is already in the userdata table, then everything
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* is already set up. */
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lua_pushvalue( L, iTable );
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lua_rawget( L, iGlobalTable );
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if( !lua_isnil(L, -1) )
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{
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void *pData = lua_touserdata( L, -1 );
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ASSERT( pSelf == pData );
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ASSERT( pSelf == lua_touserdata(L, -1) );
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lua_settop( L, iTable );
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return;
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}
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/* Create the userdata, and add it to the global table. */
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lua_pushvalue( L, iTable );
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lua_pushlightuserdata( L, pSelf );
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lua_rawset( L, iGlobalTable );
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/* Pop everything except the table. */
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lua_settop( L, iTable );
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}
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luaL_getmetatable( L, sClassName );
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lua_setmetatable( L, iTable );
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}
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#include "RageUtil_AutoPtr.h"
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REGISTER_CLASS_TRAITS( LuaClass, new LuaClass(*pCopy) )
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LuaClass::LuaClass()
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{
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m_pSelf = NULL;
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}
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void *GetUserdataFromGlobalTable( Lua *L, const char *szType, int iArg )
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{
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if( !GetGlobalTable(L, false) )
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luaL_error( L, "stale %s referenced (object used but no longer exists)", szType );
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lua_pushvalue( L, iArg );
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lua_rawget( L, -2 );
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if( lua_isnil(L, -1) )
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luaL_error( L, "stale %s referenced (object used but no longer exists)", szType );
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void *pRet = lua_touserdata( L, -1 );
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lua_pop( L, 2 );
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return pRet;
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}
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/* Tricky: when an instance table is copied, we want to do a deep
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* copy, not a reference copy. Otherwise, the new higher-level object
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* will share a table with the original. Aside from being confusing,
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* this breaks the global table, which assumes that we have a one-to-
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* one mapping between tables and objects. */
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LuaClass::LuaClass( const LuaClass &cpy ):
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LuaTable(cpy)
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{
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if( !IsSet() )
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return;
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CString sData = Serialize();
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LoadFromString( sData );
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}
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LuaClass &LuaClass::operator=( const LuaClass &cpy )
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{
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LuaTable::operator=(cpy);
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if( !IsSet() )
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return *this;
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CString sData = Serialize();
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LoadFromString( sData );
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return *this;
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}
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LuaClass::~LuaClass()
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{
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if( LUA == NULL )
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return;
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Lua *L = LUA->Get();
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int iTop = lua_gettop( L );
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/* If we're registered in the global table, unregister. */
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if( GetGlobalTable(L, false) )
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{
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this->PushSelf( L );
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lua_pushnil( L );
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lua_rawset( L, -3 );
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}
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lua_settop( L, iTop );
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LUA->Release( L );
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}
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void LuaClass::BeforeReset()
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{
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LuaTable::BeforeReset();
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/* Read pSelf the name of the class, so we can use them to restore in Register(). */
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Lua *L = LUA->Get();
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if( !GetGlobalTable(L, false) )
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{
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LUA->Release( L );
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return;
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}
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this->PushSelf( L );
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lua_rawget( L, -2 );
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if( lua_isnil(L, -1) )
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{
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/* This table hasn't been pushed yet. */
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lua_pop( L, 2 );
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LUA->Release( L );
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return;
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}
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m_pSelf = lua_touserdata( L, -1 );
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lua_pop( L, 2 );
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this->PushSelf( L );
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lua_getmetatable( L, -1 );
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lua_rawget( L, LUA_REGISTRYINDEX );
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ASSERT( !lua_isnil(L, -1) );
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m_sClassName = lua_tostring( L, -1 );
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lua_pop( L, 1 );
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LUA->Release( L );
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}
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void LuaClass::Register()
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{
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LuaTable::Register();
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if( m_pSelf != NULL )
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{
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Lua *L = LUA->Get();
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this->PushSelf(L);
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ApplyDerivedType( L, m_sClassName, m_pSelf );
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LUA->Release( L );
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/* To conserve memory, clear the class name. We only need it while restoring. */
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m_sClassName = CString();
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m_pSelf = NULL;
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}
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}
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/*
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* (c) 2005 Glenn Maynard
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* All rights reserved.
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