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   // Releases a reference on the given resource once the message loop returns.
  50   void ReleaseResourceSoon(PP_Resource res);
  51
  52   // Notifies the tracker that a new instance has been created. This must be
  53   // called before creating any resources associated with the instance.
  54   void DidCreateInstance(PP_Instance instance);
  55
  56   // Called when an instance is being deleted. All plugin refs for the
  57   // associated resources will be force freed, and the resources (if they still
  58   // exist) will be disassociated from the instance.
  59   void DidDeleteInstance(PP_Instance instance);
  60
  61   // Returns the number of resources associated with the given instance.
  62   // Returns 0 if the instance isn't known.
  63   int GetLiveObjectsForInstance(PP_Instance instance) const;
  64
  65  protected:
  66   // This calls AddResource and RemoveResource.
  67   friend class Resource;
  68
  69   // On the host-side, make sure we are called on the right thread. On the
  70   // plugin side, make sure we have the proxy lock.
  71   void CheckThreadingPreconditions() const;
  72
  73   // This method is called by PluginResourceTracker's constructor so that in
  74   // debug mode PP_Resources from the plugin process always have odd values
  75   // (ignoring the type bits), while PP_Resources from the renderer process have
  76   // even values.
  77   // This allows us to check that resource refs aren't added or released on the
  78   // wrong side.
  79   void UseOddResourceValueInDebugMode();
  80
  81   // Adds the given resource to the tracker, associating it with the instance
  82   // stored in the resource object. The new resource ID is returned, and the
  83   // resource will have 0 plugin refcount. This is called by the resource
  84   // constructor.
  85   //
  86   // Returns 0 if the resource could not be added.
  87   virtual PP_Resource AddResource(Resource* object);
  88
  89   // The opposite of AddResource, this removes the tracking information for
  90   // the given resource. It's called from the resource destructor.
  91   virtual void RemoveResource(Resource* object);
  92
  93  private:
  94   // Calls NotifyLastPluginRefWasDeleted on the given resource object and
  95   // cancels pending callbacks for the resource.
  96   void LastPluginRefWasDeleted(Resource* object);
  97
  98   int32 GetNextResourceValue();
  99
 100   // In debug mode, checks whether |res| comes from the same resource tracker.
 101   bool CanOperateOnResource(PP_Resource res);
 102
 103   typedef std::set<PP_Resource> ResourceSet;
 104
 105   struct InstanceData {
 106     // Lists all resources associated with the given instance as non-owning
 107     // pointers. This allows us to notify those resources that the instance is
 108     // going away (otherwise, they may crash if they outlive the instance).
 109     ResourceSet resources;
 110   };
 111   typedef base::hash_map<PP_Instance, linked_ptr<InstanceData> > InstanceMap;
 112
 113   InstanceMap instance_map_;
 114
 115   // For each PP_Resource, keep the object pointer and a plugin use count.
 116   // This use count is different then Resource object's RefCount, and is
 117   // manipulated using this AddRefResource/UnrefResource. When the plugin use
 118   // count is positive, we keep an extra ref on the Resource on
 119   // behalf of the plugin. When it drops to 0, we free that ref, keeping
 120   // the resource in the list.
 121   //
 122   // A resource will be in this list as long as the object is alive.
 123   typedef std::pair<Resource*, int> ResourceAndRefCount;
 124   typedef base::hash_map<PP_Resource, ResourceAndRefCount> ResourceMap;
 125   ResourceMap live_resources_;
 126
 127   int32 last_resource_value_;
 128
 129   // On the host side, we want to check that we are only called on the main
 130   // thread. This is to protect us from accidentally using the tracker from
 131   // other threads (especially the IO thread). On the plugin side, the tracker
 132   // is protected by the proxy lock and is thread-safe, so this will be NULL.
 133   scoped_ptr<base::ThreadChecker> thread_checker_;
 134
 135   base::WeakPtrFactory<ResourceTracker> weak_ptr_factory_;
 136
 137   DISALLOW_COPY_AND_ASSIGN(ResourceTracker);
 138 };
 139
 140 }  // namespace ppapi
 141
 142 #endif  // PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_