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authorRemko Tronçon <git@el-tramo.be>2009-06-01 08:48:42 (GMT)
committerRemko Tronçon <git@el-tramo.be>2009-06-01 09:24:28 (GMT)
commit2812bddd81f8a1b804c7460f4e14cd0aa393d129 (patch)
treed46294f35150c4f0f43deaf2d31fceaf945ae715 /3rdParty/Boost/boost/regex/pending/object_cache.hpp
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+/*
+ *
+ * Copyright (c) 2004
+ * 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
+{
+public:
+ typedef std::pair< ::boost::shared_ptr<Object const>, 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;
+ static boost::shared_ptr<Object const> get(const Key& k, size_type max_cache_size);
+
+private:
+ static boost::shared_ptr<Object const> do_get(const Key& k, size_type max_cache_size);
+
+ struct data
+ {
+ list_type cont;
+ map_type index;
+ };
+
+ // Needed by compilers not implementing the resolution to DR45. For reference,
+ // see http://www.open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#45.
+ friend struct data;
+};
+
+template <class Key, class Object>
+boost::shared_ptr<Object const> 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 const> 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 map_type::size_type map_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 const> result(new Object(k));
+ //
+ // Add it to the list, and index it:
+ //
+ s_data.cont.push_back(value_type(result, static_cast<Key const*>(0)));
+ s_data.index.insert(std::make_pair(k, --(s_data.cont.end())));
+ s_data.cont.back().second = &(s_data.index.find(k)->first);
+ map_size_type s = s_data.index.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