1 files changed, 89 insertions, 0 deletions
diff --git a/cache.h b/cache.h
new file mode 100755
index 0000000..b34c1c2
--- /dev/null
+++ b/cache.h
@@ -0,0 +1,89 @@
+#ifndef VGSTOOLS_CACHE_H
+#define VGSTOOLS_CACHE_H
+
+#include <algorithm>
+#include <ctime>
+#include <list>
+#include <map>
+#include <utility>
+#include "stdext.h"
+
+/*  Interface for TValue:
+ *  size_t weight() 
+ *  bool is_newer( time_t )
+ *  bool load()
+ *
+ */
+
+namespace vgstools {
+
+template< typename TKey, typename TValue >
+class cache
+{
+public:
+	typedef TKey key_type;
+	typedef TValue value_type;
+	typedef std::tr1::shared_ptr< value_type > ptr_type;
+
+private:
+	struct Value
+	{
+		ptr_type value;
+		std::time_t creation;
+
+		Value( key_type const& key )
+			: value( new value_type( key ) )
+			, creation( 0 ) {}
+	};
+
+	typedef std::list< Value > ValueList;
+	typedef std::map< TKey, typename ValueList::iterator > KeyMap;
+
+public:
+	cache( size_t maxWeight )
+			: m_maxWeight( maxWeight )
+			, m_currentWeight( 0 ) {}
+
+	size_t weight() const { return m_currentWeight; }
+	size_t count() const { return m_values.size(); }
+
+	ptr_type get( key_type const& key )
+	{
+		typename KeyMap::iterator it = m_lookup.find( key );
+		if ( it == m_lookup.end() ) {
+			typename ValueList::iterator element = m_values.insert( m_values.begin(), Value( key ) );
+			std::pair< typename KeyMap::iterator, bool > result = m_lookup.insert( std::make_pair( key, element ) );
+			it = result.first;
+		}
+
+		Value* value = &*it->second;
+		std::time_t now = std::time( 0 );
+		if ( value->creation == 0 || !value->value->is_current() ) {
+			m_currentWeight -= value->value->weight();
+			if ( !value->value->load() ) {
+				m_values.erase( it->second );
+				m_lookup.erase( it );
+				return ptr_type();
+			}
+			m_currentWeight += value->value->weight();
+			value->creation = now;
+		}
+		if ( it->second != m_values.begin() ) {
+			typename ValueList::iterator element = m_values.insert( m_values.begin(), *it->second );
+			m_values.erase( it->second );
+			it->second = element;
+			value = &*element;
+		}
+		return value->value;
+	}
+
+private:
+	std::size_t m_maxWeight;
+	std::size_t m_currentWeight;
+	ValueList m_values;
+	KeyMap m_lookup;
+};
+
+} // namespace vgstools
+
+#endif // VGSTOOLS_CACHE_H