cache StepsID::ToSteps to speed up html writing

stepmania/src/Song.cpp

@@ -339,6 +339,8 @@ void Song::RevertFromDisk( bool bAllowNotesLoss )
 			}
 		}
 	}
+
+	StepsID::FlushCache();
 }
 
 

stepmania/src/StepsUtil.cpp

@@ -154,21 +154,31 @@ void StepsID::FromSteps( const Steps *p )
  * them back out (which we don't do except in the editor), it won't be permanent. 
  * We could do this during the actual Steps::GetID() call, instead, but then it'd have
  * to have access to Song::m_LoadedFromProfile. */
+
+static map<StepsID,Steps *> g_StepsIDCache;
 Steps *StepsID::ToSteps( const Song *p, bool bAllowNull ) const
 {
 	if( st == STEPS_TYPE_INVALID || dc == DIFFICULTY_INVALID )
 		return NULL;
 
+	map<StepsID,Steps *>::iterator it = g_StepsIDCache.find( *this );
+	if( it != g_StepsIDCache.end() )
+		return it->second;
+
 	vector<Steps*> vNotes;
 	if( dc == DIFFICULTY_EDIT )
-		p->GetSteps( vNotes, st, dc, -1, -1, sDescription, true );
+		p->GetSteps( vNotes, st, dc, -1, -1, sDescription, true, 1 );
 	else
-		p->GetSteps( vNotes, st, dc, -1, -1, "", true );
+		p->GetSteps( vNotes, st, dc, -1, -1, "", true, 1 );
+
+	Steps *ret = NULL;
 	if( !vNotes.empty() )
-		return vNotes[0];
-	if( bAllowNull )
-		return NULL;
-	RageException::Throw( "%i, %i, \"%s\"", st, dc, sDescription.c_str() );	
+		ret = vNotes[0];
+	else if( !bAllowNull )
+		RageException::Throw( "%i, %i, \"%s\"", st, dc, sDescription.c_str() );	
+
+	g_StepsIDCache[*this] = ret;
+	return ret;
 }
 
 XNode* StepsID::CreateNode() const
@@ -187,6 +197,12 @@ XNode* StepsID::CreateNode() const
 	return pNode;
 }
 
+
+void StepsID::FlushCache()
+{
+	g_StepsIDCache.clear();
+}
+
 void StepsID::LoadFromNode( const XNode* pNode ) 
 {
 	ASSERT( pNode->name == "Steps" );

stepmania/src/StepsUtil.h

@@ -51,6 +51,7 @@ public:
 	void LoadFromNode( const XNode* pNode );
 	CString ToString() const;
 	bool IsValid() const;
+	static void FlushCache();
 };
 
 #endif