Cloning a bunch of stuff from the native_client repository at r6528

ppapi/native_client/src/shared/ppapi_proxy/plugin_resource_tracker.h

+// Copyright (c) 2011 The Native Client Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WEBKIT_GLUE_PLUGINS_PEPPER_RESOURCE_TRACKER_H_
+#define WEBKIT_GLUE_PLUGINS_PEPPER_RESOURCE_TRACKER_H_
+
+#include <map>
+#include <utility>
+
+#include "native_client/src/include/nacl_base.h"
+#include "native_client/src/include/ref_counted.h"
+#include "ppapi/c/pp_instance.h"
+#include "ppapi/c/pp_module.h"
+#include "ppapi/c/pp_resource.h"
+
+namespace ppapi_proxy {
+
+class PluginInstance;
+class PluginResource;
+
+// This class maintains a global list of all live pepper resources. It allows
+// us to check resource ID validity and to map them to a specific module.
+//
+// This object is threadsafe.
+class PluginResourceTracker {
+ public:
+  // Returns the pointer to the singleton object.
+  static PluginResourceTracker* Get() {
+    static PluginResourceTracker tracker;
+    return &tracker;
+  }
+
+  // PP_Resources --------------------------------------------------------------
+
+  // Increment resource's plugin refcount. See ResourceAndRefCount.
+  bool AddRefResource(PP_Resource res);
+  bool UnrefResource(PP_Resource res);
+
+ private:
+  friend class PluginResource;
+
+  // Prohibit creation other then by the Singleton class.
+  PluginResourceTracker();
+
+  // Adds the given resource to the tracker and assigns it a resource ID, local
+  // refcount of 1, and initializes the browser reference count to
+  // |browser_refcount|. Used only by the Resource class.
+  void AddResource(PluginResource* resource, PP_Resource id,
+                   size_t browser_refcount);
+
+  // The returned pointer will be NULL if there is no resource. Note that this
+  // return value is a scoped_refptr so that we ensure the resource is valid
+  // from the point of the lookup to the point that the calling code needs it.
+  // Otherwise, the plugin could Release() the resource on another thread and
+  // the object will get deleted out from under us.
+  scoped_refptr<PluginResource> GetExistingResource(PP_Resource res) const;
+
+  // Get or create a new PluginResource from a browser resource.
+  // If we are already tracking this resource, we bump its browser_refcount to
+  // reflect that we took ownership of it. If this is a new resource, we create
+  // a PluginResource for it with the given browser_refcount.
+  template<typename T> scoped_refptr<T> AdoptBrowserResource(
+      PP_Resource res, size_t browser_refcount);
+
+  // Try to get a browser-side refcount for an existing resource.
+  void ObtainBrowserResource(PP_Resource res);
+
+  // Release browser-side refcount.
+  void ReleaseBrowserResource(PP_Resource res, size_t refcount);
+
+  // Last assigned resource ID.
+  PP_Resource last_id_;
+
+  struct ResourceAndRefCounts {
+    scoped_refptr<PluginResource> resource;
+    size_t browser_refcount;
+    size_t plugin_refcount;
+    ResourceAndRefCounts(PluginResource* r, size_t browser_refcount);
+    ~ResourceAndRefCounts();
+  };
+  typedef std::map<PP_Resource, ResourceAndRefCounts> ResourceMap;
+  ResourceMap live_resources_;
+
+  DISALLOW_COPY_AND_ASSIGN(PluginResourceTracker);
+};
+
+}  // namespace ppapi_proxy
+
+#endif  // WEBKIT_GLUE_PLUGINS_PEPPER_RESOURCE_TRACKER_H_
+