perf: reintroduce KeyValues cache with sv_pure support

InvalidCache every time we do a pure reload, technically
we could be more selective but lots of other systems also
do a similar full reload of files so I think it's fine

this improves performance of mostly material queries
but also some specific weapon data queries

Author: mastercoms

src/engine/cl_main.cpp

@@ -181,6 +181,11 @@ void CL_ReloadFilesInList( IFileList *pFilesToReload )
 
 	ResourceLocker crashPreventer;
 
+	// Handle KeyValues
+	// TODO: only reload paths we need to reload
+	// this is still better than completely disabling the KV cache...
+	KeyValuesSystem()->InvalidateCache();
+
 	// Handle materials..
 	materials->ReloadFilesInList( pFilesToReload );
 
@@ -406,12 +411,12 @@ void WriteConfig_f( ConVar *var, const char *pOldString )
 void CL_CheckClientState( void )
 {
 	// Setup the local network backdoor (we do this each frame so it can be toggled on and off).
-	bool useBackdoor = cl_LocalNetworkBackdoor.GetInt() && 
+	bool useBackdoor = cl_LocalNetworkBackdoor.GetInt() &&
+						Host_IsSinglePlayerGame() &&
 						(cl.m_NetChannel ? cl.m_NetChannel->IsLoopback() : false) &&
 						sv.IsActive() &&
 						!demorecorder->IsRecording() &&
-						!demoplayer->IsPlayingBack() &&
-						Host_IsSinglePlayerGame();
+						!demoplayer->IsPlayingBack();
 
 	CL_SetupLocalNetworkBackDoor( useBackdoor );
 }

src/tier1/KeyValues.cpp

@@ -534,6 +534,7 @@ const char *KeyValues::GetName( void ) const
 //-----------------------------------------------------------------------------
 // Purpose: Read a single token from buffer (0 terminated)
 //-----------------------------------------------------------------------------
+#pragma warning( push )
 #pragma warning (disable:4706)
 const char *KeyValues::ReadToken( CUtlBuffer &buf, bool &wasQuoted, bool &wasConditional )
 {
@@ -618,7 +619,7 @@ const char *KeyValues::ReadToken( CUtlBuffer &buf, bool &wasQuoted, bool &wasCon
 	s_pTokenBuf[ nCount ] = 0;
 	return s_pTokenBuf;
 }
-#pragma warning (default:4706)
+#pragma warning( pop )
 
 
 
@@ -681,7 +682,8 @@ bool KeyValues::LoadFromFile( IBaseFileSystem *filesystem, const char *resourceN
 	So all vmt's files can bypass sv_pure 1. And I believe this mod is mostly
 	made of vmt files, so valve's sv_pure 1 bull is pretty redundant.
 	*/
-	const bool bUseCache = false;
+	// UNDONE: the above exploit is no longer relevant because the KeyValues cache is now invalidated for sv_pure
+	const bool bUseCache = s_pfGetSymbolForString == KeyValues::GetSymbolForStringClassic;
 #endif
 
 	// If pathID is null, we cannot cache the result because that has a weird iterate-through-a-bunch-of-locations behavior.