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_VAR_TRACKER_H_ 6 #define PPAPI_SHARED_IMPL_VAR_TRACKER_H_ 7 8 #include <vector> 9 10 #include "base/basictypes.h" 11 #include "base/containers/hash_tables.h" 12 #include "base/memory/ref_counted.h" 13 #include "base/memory/scoped_ptr.h" 14 #include "base/memory/shared_memory.h" 15 #include "base/threading/thread_checker.h" 16 #include "ppapi/c/pp_instance.h" 17 #include "ppapi/c/pp_module.h" 18 #include "ppapi/c/pp_resource.h" 19 #include "ppapi/c/pp_var.h" 20 #include "ppapi/shared_impl/host_resource.h" 21 #include "ppapi/shared_impl/ppapi_shared_export.h" 22 #include "ppapi/shared_impl/var.h" 23 24 namespace ppapi { 25 26 class ArrayBufferVar; 27 28 // Tracks non-POD (refcounted) var objects held by a plugin. 29 // 30 // The tricky part is the concept of a "tracked object". These are only 31 // necessary in the plugin side of the proxy when running out of process. A 32 // tracked object is one that the plugin is aware of, but doesn't hold a 33 // reference to. This will happen when the plugin is passed an object as an 34 // argument from the host (renderer) as an input argument to a sync function, 35 // but where ownership is not passed. 36 // 37 // This class maintains the "track_with_no_reference_count" but doesn't do 38 // anything with it other than call virtual functions. The interesting parts 39 // are added by the PluginObjectVar derived from this class. 40 class PPAPI_SHARED_EXPORT VarTracker { 41 public: 42 // A SINGLE_THREADED VarTracker will use a thread-checker to make sure it's 43 // always invoked on the same thread on which it was constructed. A 44 // THREAD_SAFE VarTracker will check that the ProxyLock is held. See 45 // CheckThreadingPreconditions() for more details. 46 enum ThreadMode { SINGLE_THREADED, THREAD_SAFE }; 47 explicit VarTracker(ThreadMode thread_mode); 48 virtual ~VarTracker(); 49 50 // Called by the Var object to add a new var to the tracker. 51 int32 AddVar(Var* var); 52 53 // Looks up a given var and returns a reference to the Var if it exists. 54 // Returns NULL if the var type is not an object we track (POD) or is 55 // invalid. 56 Var* GetVar(int32 var_id) const; 57 Var* GetVar(const PP_Var& var) const; 58 59 // Increases a previously-known Var ID's refcount, returning true on success, 60 // false if the ID is invalid. The PP_Var version returns true and does 61 // nothing for non-refcounted type vars. 62 bool AddRefVar(int32 var_id); 63 bool AddRefVar(const PP_Var& var); 64 65 // Decreases the given Var ID's refcount, returning true on success, false if 66 // the ID is invalid or if the refcount was already 0. The PP_Var version 67 // returns true and does nothing for non-refcounted type vars. The var will 68 // be deleted if there are no more refs to it. 69 bool ReleaseVar(int32 var_id); 70 bool ReleaseVar(const PP_Var& var); 71 72 // Create a new array buffer of size |size_in_bytes|. Return a PP_Var that 73 // that references it and has an initial reference-count of 1. 74 PP_Var MakeArrayBufferPPVar(uint32 size_in_bytes); 75 // Same as above, but copy the contents of |data| in to the new array buffer. 76 PP_Var MakeArrayBufferPPVar(uint32 size_in_bytes, const void* data); 77 // Same as above, but copy the contents of the shared memory in |h| 78 // into the new array buffer. 79 PP_Var MakeArrayBufferPPVar(uint32 size_in_bytes, 80 base::SharedMemoryHandle h); 81 82 // Create an ArrayBuffer and copy the contents of |data| in to it. The 83 // returned object has 0 reference count in the tracker, and like all 84 // RefCounted objects, has a 0 initial internal reference count. (You should 85 // usually immediately put this in a scoped_refptr). 86 ArrayBufferVar* MakeArrayBufferVar(uint32 size_in_bytes, const void* data); 87 88 // Return a vector containing all PP_Vars that are in the tracker. This is 89 // to help implement PPB_Testing_Dev.GetLiveVars and should generally not be 90 // used in production code. The PP_Vars are returned in no particular order, 91 // and their reference counts are unaffected. 92 std::vector<PP_Var> GetLiveVars(); 93 94 // Retrieves the internal reference counts for testing. Returns 0 if we 95 // know about the object but the corresponding value is 0, or -1 if the 96 // given object ID isn't in our map. 97 int GetRefCountForObject(const PP_Var& object); 98 int GetTrackedWithNoReferenceCountForObject(const PP_Var& object); 99 100 // Returns true if the given vartype is refcounted and has associated objects 101 // (it's not POD). 102 static bool IsVarTypeRefcounted(PP_VarType type); 103 104 // Called after an instance is deleted to do var cleanup. 105 virtual void DidDeleteInstance(PP_Instance instance) = 0; 106 107 // Returns an "id" for a shared memory handle that can be safely sent between 108 // the host and plugin, and resolved back into the original handle on the 109 // host. Not implemented on the plugin side. 110 virtual int TrackSharedMemoryHandle(PP_Instance instance, 111 base::SharedMemoryHandle handle, 112 uint32 size_in_bytes) = 0; 113 114 // Resolves an "id" generated by TrackSharedMemoryHandle back into 115 // a SharedMemory handle and its size on the host. 116 // Not implemented on the plugin side. 117 virtual bool StopTrackingSharedMemoryHandle( 118 int id, 119 PP_Instance instance, 120 base::SharedMemoryHandle *handle, 121 uint32* size_in_bytes) = 0; 122 123 protected: 124 struct PPAPI_SHARED_EXPORT VarInfo { 125 VarInfo(); 126 VarInfo(Var* v, int input_ref_count); 127 128 scoped_refptr<Var> var; 129 130 // Explicit reference count. This value is affected by the renderer calling 131 // AddRef and Release. A nonzero value here is represented by a single 132 // reference in the host on our behalf (this reduces IPC traffic). 133 int ref_count; 134 135 // Tracked object count (see class comment above). 136 // 137 // "TrackObjectWithNoReference" might be called recursively in rare cases. 138 // For example, say the host calls a plugin function with an object as an 139 // argument, and in response, the plugin calls a host function that then 140 // calls another (or the same) plugin function with the same object. 141 // 142 // This value tracks the number of calls to TrackObjectWithNoReference so 143 // we know when we can stop tracking this object. 144 int track_with_no_reference_count; 145 }; 146 typedef base::hash_map<int32, VarInfo> VarMap; 147 148 // Specifies what should happen with the refcount when calling AddVarInternal. 149 enum AddVarRefMode { 150 ADD_VAR_TAKE_ONE_REFERENCE, 151 ADD_VAR_CREATE_WITH_NO_REFERENCE 152 }; 153 154 // On the host-side, make sure we are called on the right thread. On the 155 // plugin side, make sure we have the proxy lock. 156 void CheckThreadingPreconditions() const; 157 158 // Implementation of AddVar that allows the caller to specify whether the 159 // initial refcount of the added object will be 0 or 1. 160 // 161 // Overridden in the plugin proxy to do additional object tracking. 162 virtual int32 AddVarInternal(Var* var, AddVarRefMode mode); 163 164 // Convenience functions for doing lookups into the live_vars_ map. 165 VarMap::iterator GetLiveVar(int32 id); 166 VarMap::iterator GetLiveVar(const PP_Var& var); 167 VarMap::const_iterator GetLiveVar(const PP_Var& var) const; 168 169 // Called when AddRefVar increases a "tracked" ProxyObject's refcount from 170 // zero to one. In the plugin side of the proxy, we need to send some 171 // messages to the host. In the host side, this should never be called since 172 // there are no proxy objects. 173 virtual void TrackedObjectGettingOneRef(VarMap::const_iterator iter); 174 175 // Called when ReleaseVar decreases a object's refcount from one to zero. It 176 // may still be "tracked" (has a "track_with_no_reference_count") value. In 177 // the plugin side of the proxy, we need to tell the host that we no longer 178 // have a reference. In the host side, this should never be called since 179 // there are no proxy objects. 180 virtual void ObjectGettingZeroRef(VarMap::iterator iter); 181 182 // Called when an object may have had its refcount or 183 // track_with_no_reference_count value decreased. If the object has neither 184 // refs anymore, this will remove it and return true. Returns false if it's 185 // still alive. 186 // 187 // Overridden by the PluginVarTracker to also clean up the host info map. 188 virtual bool DeleteObjectInfoIfNecessary(VarMap::iterator iter); 189 190 VarMap live_vars_; 191 192 // Last assigned var ID. 193 int32 last_var_id_; 194 195 private: 196 // Create and return a new ArrayBufferVar size_in_bytes bytes long. This is 197 // implemented by the Host and Plugin tracker separately, so that it can be 198 // a real WebKit ArrayBuffer on the host side. 199 virtual ArrayBufferVar* CreateArrayBuffer(uint32 size_in_bytes) = 0; 200 virtual ArrayBufferVar* CreateShmArrayBuffer( 201 uint32 size_in_bytes, 202 base::SharedMemoryHandle handle) = 0; 203 204 // On the host side, we want to check that we are only called on the main 205 // thread. This is to protect us from accidentally using the tracker from 206 // other threads (especially the IO thread). On the plugin side, the tracker 207 // is protected by the proxy lock and is thread-safe, so this will be NULL. 208 scoped_ptr<base::ThreadChecker> thread_checker_; 209 210 DISALLOW_COPY_AND_ASSIGN(VarTracker); 211 }; 212 213 } // namespace ppapi 214 215 #endif // PPAPI_SHARED_IMPL_VAR_TRACKER_H_ 216
