--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Plugin/ViewerPrefetchPolicy.cpp	Wed Feb 25 13:45:35 2015 +0100
@@ -0,0 +1,160 @@
+/**
+ * Orthanc - A Lightweight, RESTful DICOM Store
+ * Copyright (C) 2012-2015 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, 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 "ViewerPrefetchPolicy.h"
+
+#include "ViewerToolbox.h"
+#include "Cache/CacheScheduler.h"
+
+#include <json/value.h>
+#include <json/reader.h>
+
+
+
+static const Json::Value::ArrayIndex PREFETCH_FORWARD = 10;
+static const Json::Value::ArrayIndex PREFETCH_BACKWARD = 3;
+
+
+namespace OrthancPlugins
+{
+  void ViewerPrefetchPolicy::ApplySeries(std::list<CacheIndex>& toPrefetch,
+                                         CacheScheduler& cache,
+                                         const std::string& series,
+                                         const std::string& content)
+  {
+    Json::Value json;
+    Json::Reader reader;
+    if (!reader.parse(content, json) ||
+        !json.isMember("SortedInstances"))
+    {
+      return;
+    }
+
+    const Json::Value& instances = json["SortedInstances"];
+    if (instances.type() != Json::arrayValue)
+    {
+      return;
+    }
+
+    for (Json::Value::ArrayIndex i = 0; 
+         i < instances.size() && i < PREFETCH_FORWARD; 
+         i++)
+    {
+      std::string item = "jpeg95-" + instances[i].asString();
+      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
+    }
+  }
+
+
+  void ViewerPrefetchPolicy::ApplyInstance(std::list<CacheIndex>& toPrefetch,
+                                           CacheScheduler& cache,
+                                           const std::string& path)
+  {
+    size_t separator = path.find('-');
+    if (separator == std::string::npos)
+    {
+      return;
+    }
+
+    std::string compression = path.substr(0, separator + 1);
+    std::string instanceId = path.substr(separator + 1);
+
+    Json::Value instance;
+    if (!GetJsonFromOrthanc(instance, context_, "/instances/" + instanceId) ||
+        !instance.isMember("ParentSeries"))
+    {
+      return;
+    }
+
+    std::string tmp;
+    if (!cache.Access(tmp, CacheBundle_SeriesInformation, instance["ParentSeries"].asString()))
+    {
+      return;
+    }
+    
+    Json::Value series;
+    Json::Reader reader;
+    if (!reader.parse(tmp, series) ||
+        !series.isMember("SortedInstances"))
+    {
+      return;
+    }
+
+    const Json::Value& instances = series["SortedInstances"];
+    if (instances.type() != Json::arrayValue)
+    {
+      return;
+    }
+
+    Json::Value::ArrayIndex position = 0;
+    while (position < instances.size())
+    {
+      if (instances[position] == instanceId)
+      {
+        break;
+      }
+
+      position++;
+    }
+
+    if (position == instances.size())
+    {
+      return;
+    }
+
+    for (Json::Value::ArrayIndex i = position;
+         i < instances.size() && i < position + PREFETCH_FORWARD; 
+         i++)
+    {
+      std::string item = compression + instances[i].asString();
+      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
+    }
+
+    for (Json::Value::ArrayIndex i = position;
+         i >= 0 && i > position - PREFETCH_BACKWARD; )
+    {
+      i--;
+      std::string item = compression + instances[i].asString();
+      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
+    }
+  }
+
+
+  void ViewerPrefetchPolicy::Apply(std::list<CacheIndex>& toPrefetch,
+                                   CacheScheduler& cache,
+                                   const CacheIndex& accessed,
+                                   const std::string& content)
+  {
+    switch (accessed.GetBundle())
+    {
+      case CacheBundle_SeriesInformation:
+        ApplySeries(toPrefetch, cache, accessed.GetItem(), content);
+        return;
+
+      case CacheBundle_DecodedImage:
+        ApplyInstance(toPrefetch, cache, accessed.GetItem());
+        return;
+
+      default:
+        return;
+    }
+  }
+}
+