ppapi/shared_impl/resource_tracker.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_
   6 #define PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_
   7
   8 #include <set>
   9
  10 #include "base/basictypes.h"
  11 #include "base/containers/hash_tables.h"
  12 #include "base/memory/linked_ptr.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/memory/weak_ptr.h"
  15 #include "base/threading/thread_checker.h"
  16 #include "base/threading/thread_checker_impl.h"
  17 #include "ppapi/c/pp_instance.h"
  18 #include "ppapi/c/pp_resource.h"
  19 #include "ppapi/shared_impl/ppapi_shared_export.h"
  20
  21 namespace ppapi {
  22
  23 class Resource;
  24
  25 class PPAPI_SHARED_EXPORT ResourceTracker {
  26  public:
  27   // A SINGLE_THREADED ResourceTracker will use a thread-checker to make sure
  28   // it's always invoked on the same thread on which it was constructed. A
  29   // THREAD_SAFE ResourceTracker will check that the ProxyLock is held. See
  30   // CheckThreadingPreconditions() for more details.
  31   enum ThreadMode { SINGLE_THREADED, THREAD_SAFE };
  32   explicit ResourceTracker(ThreadMode thread_mode);
  33   virtual ~ResourceTracker();
  34
  35   // The returned pointer will be NULL if there is no resource. The reference
  36   // count of the resource is unaffected.
  37   Resource* GetResource(PP_Resource res) const;
  38
  39   // Takes a reference on the given resource.
  40   // Do not call this method on on the host side for resources backed by a
  41   // ResourceHost.
  42   void AddRefResource(PP_Resource res);
  43
  44   // Releases a reference on the given resource.
  45   // Do not call this method on on the host side for resources backed by a
  46   // ResourceHost.
  47   void ReleaseResource(PP_Resource res);
  48
  49   // Notifies the tracker that a new instance has been created. This must be
  50   // called before creating any resources associated with the instance.
  51   void DidCreateInstance(PP_Instance instance);
  52
  53   // Called when an instance is being deleted. All plugin refs for the
  54   // associated resources will be force freed, and the resources (if they still
  55   // exist) will be disassociated from the instance.
  56   void DidDeleteInstance(PP_Instance instance);
  57
  58   // Returns the number of resources associated with the given instance.
  59   // Returns 0 if the instance isn't known.
  60   int GetLiveObjectsForInstance(PP_Instance instance) const;
  61
  62  protected:
  63   // This calls AddResource and RemoveResource.
  64   friend class Resource;
  65
  66   // On the host-side, make sure we are called on the right thread. On the
  67   // plugin side, make sure we have the proxy lock.
  68   void CheckThreadingPreconditions() const;
  69
  70   // This method is called by PluginResourceTracker's constructor so that in
  71   // debug mode PP_Resources from the plugin process always have odd values
  72   // (ignoring the type bits), while PP_Resources from the renderer process have
  73   // even values.
  74   // This allows us to check that resource refs aren't added or released on the
  75   // wrong side.
  76   void UseOddResourceValueInDebugMode();
  77
  78   // Adds the given resource to the tracker, associating it with the instance
  79   // stored in the resource object. The new resource ID is returned, and the
  80   // resource will have 0 plugin refcount. This is called by the resource
  81   // constructor.
  82   //
  83   // Returns 0 if the resource could not be added.
  84   virtual PP_Resource AddResource(Resource* object);
  85
  86   // The opposite of AddResource, this removes the tracking information for
  87   // the given resource. It's called from the resource destructor.
  88   virtual void RemoveResource(Resource* object);
  89
  90  private:
  91   // Calls NotifyLastPluginRefWasDeleted on the given resource object and
  92   // cancels pending callbacks for the resource.
  93   void LastPluginRefWasDeleted(Resource* object);
  94
  95   int32 GetNextResourceValue();
  96
  97   // In debug mode, checks whether |res| comes from the same resource tracker.
  98   bool CanOperateOnResource(PP_Resource res);
  99
 100   typedef std::set<PP_Resource> ResourceSet;
 101
 102   struct InstanceData {
 103     // Lists all resources associated with the given instance as non-owning
 104     // pointers. This allows us to notify those resources that the instance is
 105     // going away (otherwise, they may crash if they outlive the instance).
 106     ResourceSet resources;
 107   };
 108   typedef base::hash_map<PP_Instance, linked_ptr<InstanceData> > InstanceMap;
 109
 110   InstanceMap instance_map_;
 111
 112   // For each PP_Resource, keep the object pointer and a plugin use count.
 113   // This use count is different then Resource object's RefCount, and is
 114   // manipulated using this AddRefResource/UnrefResource. When the plugin use
 115   // count is positive, we keep an extra ref on the Resource on
 116   // behalf of the plugin. When it drops to 0, we free that ref, keeping
 117   // the resource in the list.
 118   //
 119   // A resource will be in this list as long as the object is alive.
 120   typedef std::pair<Resource*, int> ResourceAndRefCount;
 121   typedef base::hash_map<PP_Resource, ResourceAndRefCount> ResourceMap;
 122   ResourceMap live_resources_;
 123
 124   int32 last_resource_value_;
 125
 126   // On the host side, we want to check that we are only called on the main
 127   // thread. This is to protect us from accidentally using the tracker from
 128   // other threads (especially the IO thread). On the plugin side, the tracker
 129   // is protected by the proxy lock and is thread-safe, so this will be NULL.
 130   scoped_ptr<base::ThreadChecker> thread_checker_;
 131
 132   base::WeakPtrFactory<ResourceTracker> weak_ptr_factory_;
 133
 134   DISALLOW_COPY_AND_ASSIGN(ResourceTracker);
 135 };
 136
 137 }  // namespace ppapi
 138
 139 #endif  // PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_