--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Plugin/MemoryCache.cpp	Wed Mar 22 16:13:52 2017 +0100
@@ -0,0 +1,161 @@
+/**
+ * Advanced authorization plugin for Orthanc
+ * Copyright (C) 2017 Osimis, Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#include "MemoryCache.h"
+
+namespace OrthancPlugins
+{
+  class MemoryCache::Payload : public boost::noncopyable
+  {
+  private:
+    bool                     hasExpiration_;
+    boost::posix_time::ptime expiration_;
+    std::string              value_;
+
+  public:
+    Payload(const std::string& value,
+            unsigned int validity) :
+      value_(value)
+    {
+      if (validity == 0)
+      {
+        hasExpiration_ = false;
+      }
+      else
+      {
+        hasExpiration_ = true;
+        expiration_ = (boost::posix_time::second_clock::local_time() +
+                       boost::posix_time::seconds(validity));
+      }
+    }
+
+    bool HasExpired() const
+    {
+      return (hasExpiration_ &&
+              boost::posix_time::second_clock::local_time() >= expiration_);
+    }
+      
+    bool GetValue(std::string& target) const
+    {
+      if (HasExpired())
+      {
+        return false;
+      }
+      else
+      {
+        target = value_;
+        return true;          
+      }
+    }
+  };
+    
+   
+  void MemoryCache::RemoveOldest()
+  {
+    Payload* payload = NULL;
+    index_.RemoveOldest(payload);
+    assert(payload != NULL);
+    delete payload;
+  }
+
+  
+  void MemoryCache::InvalidateInternal(const std::string& key)
+  {
+    Payload* payload = NULL;
+
+    if (index_.Contains(key, payload))
+    {
+      assert(payload != NULL);
+      delete payload;
+      index_.Invalidate(key);
+    }
+  }
+    
+
+  MemoryCache::MemoryCache(unsigned int maxSize) :
+    maxSize_(maxSize)
+  {
+    if (maxSize_ == 0)
+    {
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange);
+    }
+  }
+
+    
+  MemoryCache::~MemoryCache()
+  {
+    while (!index_.IsEmpty())
+    {
+      RemoveOldest();
+    }
+  }
+    
+
+  void MemoryCache::Invalidate(const std::string& key)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+    InvalidateInternal(key);
+  }
+
+
+  void MemoryCache::Store(const std::string& key,
+                          const std::string& value,
+                          unsigned int expiration /* in seconds */)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+
+    InvalidateInternal(key);
+
+    if (index_.GetSize() == maxSize_)
+    {
+      // The cache is full: Make some room
+      RemoveOldest();
+    }
+        
+    index_.Add(key, new Payload(value, expiration));
+  }
+
+
+  bool MemoryCache::Retrieve(std::string& value,
+                             const std::string& key)
+  {
+    boost::mutex::scoped_lock lock(mutex_);
+
+    Payload* payload = NULL;
+      
+    if (!index_.Contains(key, payload))
+    {
+      return false;
+    }
+      
+    assert(payload != NULL);
+      
+    if (payload->GetValue(value))
+    {
+      index_.MakeMostRecent(key);
+      return true;
+    }
+    else
+    {
+      // The value has expired in the cache: Invalidate it
+      delete payload;
+      index_.Invalidate(key);
+      return false;
+    }
+  }
+}