merged changes in regex5 branch

[SVN r26692]

include/boost/regex/pending/object_cache.hpp

@@ -0,0 +1,159 @@
+/*
+ *
+ * Copyright (c) 2004
+ * Dr John Maddock
+ *
+ * Use, modification and distribution are subject to the 
+ * Boost Software License, Version 1.0. (See accompanying file 
+ * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ *
+ */
+
+ /*
+  *   LOCATION:    see http://www.boost.org for most recent version.
+  *   FILE         object_cache.hpp
+  *   VERSION      see <boost/version.hpp>
+  *   DESCRIPTION: Implements a generic object cache.
+  */
+
+#ifndef BOOST_REGEX_OBJECT_CACHE_HPP
+#define BOOST_REGEX_OBJECT_CACHE_HPP
+
+#include <map>
+#include <list>
+#include <stdexcept>
+#include <string>
+#include <boost/config.hpp>
+#include <boost/shared_ptr.hpp>
+#ifdef BOOST_HAS_THREADS
+#include <boost/regex/pending/static_mutex.hpp>
+#endif
+
+namespace boost{
+
+template <class Key, class Object>
+class object_cache
+{
+   typedef std::pair< ::boost::shared_ptr<Object>, Key const*> value_type;
+   typedef std::list<value_type> list_type;
+   typedef typename list_type::iterator list_iterator;
+   typedef std::map<Key, list_iterator> map_type;
+   typedef typename map_type::iterator map_iterator;
+   typedef typename list_type::size_type size_type;
+public:
+   static boost::shared_ptr<Object> get(const Key& k, size_type max_cache_size);
+
+private:
+   static boost::shared_ptr<Object> do_get(const Key& k, size_type max_cache_size);
+
+   struct data
+   {
+      list_type   cont;
+      map_type    index;
+   };
+};
+
+template <class Key, class Object>
+boost::shared_ptr<Object> object_cache<Key, Object>::get(const Key& k, size_type max_cache_size)
+{
+#ifdef BOOST_HAS_THREADS
+   static boost::static_mutex mut = BOOST_STATIC_MUTEX_INIT;
+
+   boost::static_mutex::scoped_lock l(mut);
+   if(l)
+   {
+      return do_get(k, max_cache_size);
+   }
+   //
+   // what do we do if the lock fails?
+   // for now just throw, but we should never really get here...
+   //
+   ::boost::throw_exception(std::runtime_error("Error in thread safety code: could not acquire a lock"));
+   return boost::shared_ptr<Object>();
+#else
+   return do_get(k, max_cache_size);
+#endif
+}
+
+template <class Key, class Object>
+boost::shared_ptr<Object> object_cache<Key, Object>::do_get(const Key& k, size_type max_cache_size)
+{
+   typedef typename object_cache<Key, Object>::data object_data;
+   typedef typename list_type::size_type list_size_type;
+   static object_data s_data;
+
+   //
+   // see if the object is already in the cache:
+   //
+   map_iterator mpos = s_data.index.find(k);
+   if(mpos != s_data.index.end())
+   {
+      //
+      // Eureka! 
+      // We have a cached item, bump it up the list and return it:
+      //
+      if(--(s_data.cont.end()) != mpos->second)
+      {
+         // splice out the item we want to move:
+         list_type temp;
+         temp.splice(temp.end(), s_data.cont, mpos->second);
+         // and now place it at the end of the list:
+         s_data.cont.splice(s_data.cont.end(), temp, temp.begin());
+         BOOST_ASSERT(*(s_data.cont.back().second) == k);
+         // update index with new position:
+         mpos->second = --(s_data.cont.end());
+         BOOST_ASSERT(&(mpos->first) == mpos->second->second);
+         BOOST_ASSERT(&(mpos->first) == s_data.cont.back().second);
+      }
+      return s_data.cont.back().first;
+   }
+   //
+   // if we get here then the item is not in the cache,
+   // so create it:
+   //
+   boost::shared_ptr<Object> result(new Object(k));
+   //
+   // Add it to the list, and index it:
+   //
+   s_data.cont.push_back(value_type(result, 0));
+   s_data.index[k] = --(s_data.cont.end());
+   s_data.cont.back().second = &(s_data.index.find(k)->first);
+   list_size_type s = s_data.cont.size();
+   BOOST_ASSERT(s_data.index[k]->first.get() == result.get());
+   BOOST_ASSERT(&(s_data.index.find(k)->first) == s_data.cont.back().second);
+   BOOST_ASSERT(s_data.index.find(k)->first == k);
+   if(s > max_cache_size)
+   {
+      //
+      // We have too many items in the list, so we need to start
+      // popping them off the back of the list, but only if they're
+      // being held uniquely by us:
+      //
+      list_iterator pos = s_data.cont.begin();
+      list_iterator last = s_data.cont.end();
+      while((pos != last) && (s > max_cache_size))
+      {
+         if(pos->first.unique())
+         {
+            list_iterator condemmed(pos);
+            ++pos;
+            // now remove the items from our containers, 
+            // then order has to be as follows:
+            BOOST_ASSERT(s_data.index.find(*(condemmed->second)) != s_data.index.end());
+            s_data.index.erase(*(condemmed->second));
+            s_data.cont.erase(condemmed); 
+            --s;
+         }
+         else
+            --pos;
+      }
+      BOOST_ASSERT(s_data.index[k]->first.get() == result.get());
+      BOOST_ASSERT(&(s_data.index.find(k)->first) == s_data.cont.back().second);
+      BOOST_ASSERT(s_data.index.find(k)->first == k);
+   }
+   return result;
+}
+
+}
+
+#endif