var_tracker.h revision 5821806d5e7f356e8fa4b058a389a808ea183019
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/hash_tables.h" 12#include "base/memory/ref_counted.h" 13#include "base/threading/non_thread_safe.h" 14#include "ppapi/c/pp_instance.h" 15#include "ppapi/c/pp_module.h" 16#include "ppapi/c/pp_var.h" 17#include "ppapi/shared_impl/ppapi_shared_export.h" 18 19namespace ppapi { 20 21class ArrayBufferVar; 22class Var; 23 24// Tracks non-POD (refcounted) var objects held by a plugin. 25// 26// The tricky part is the concept of a "tracked object". These are only 27// necessary in the plugin side of the proxy when running out of process. A 28// tracked object is one that the plugin is aware of, but doesn't hold a 29// reference to. This will happen when the plugin is passed an object as an 30// argument from the host (renderer) as an input argument to a sync function, 31// but where ownership is not passed. 32// 33// This class maintains the "track_with_no_reference_count" but doesn't do 34// anything with it other than call virtual functions. The interesting parts 35// are added by the PluginObjectVar derived from this class. 36class PPAPI_SHARED_EXPORT VarTracker 37#ifdef ENABLE_PEPPER_THREADING 38 : NON_EXPORTED_BASE(public base::NonThreadSafeDoNothing) { 39#else 40 // TODO(dmichael): Remove the thread checking when calls are allowed off the 41 // main thread (crbug.com/92909). 42 : NON_EXPORTED_BASE(public base::NonThreadSafe) { 43#endif 44 public: 45 VarTracker(); 46 virtual ~VarTracker(); 47 48 // Called by the Var object to add a new var to the tracker. 49 int32 AddVar(Var* var); 50 51 // Looks up a given var and returns a reference to the Var if it exists. 52 // Returns NULL if the var type is not an object we track (POD) or is 53 // invalid. 54 Var* GetVar(int32 var_id) const; 55 Var* GetVar(const PP_Var& var) const; 56 57 // Increases a previously-known Var ID's refcount, returning true on success, 58 // false if the ID is invalid. The PP_Var version returns true and does 59 // nothing for non-refcounted type vars. 60 bool AddRefVar(int32 var_id); 61 bool AddRefVar(const PP_Var& var); 62 63 // Decreases the given Var ID's refcount, returning true on success, false if 64 // the ID is invalid or if the refcount was already 0. The PP_Var version 65 // returns true and does nothing for non-refcounted type vars. The var will 66 // be deleted if there are no more refs to it. 67 bool ReleaseVar(int32 var_id); 68 bool ReleaseVar(const PP_Var& var); 69 70 // Create a new array buffer of size |size_in_bytes|. Return a PP_Var that 71 // that references it and has an initial reference-count of 1. 72 PP_Var MakeArrayBufferPPVar(uint32 size_in_bytes); 73 // Same as above, but copy the contents of |data| in to the new array buffer. 74 PP_Var MakeArrayBufferPPVar(uint32 size_in_bytes, const void* data); 75 76 // Return a vector containing all PP_Vars that are in the tracker. This is 77 // to help implement PPB_Testing_Dev.GetLiveVars and should generally not be 78 // used in production code. The PP_Vars are returned in no particular order, 79 // and their reference counts are unaffected. 80 std::vector<PP_Var> GetLiveVars(); 81 82 // Retrieves the internal reference counts for testing. Returns 0 if we 83 // know about the object but the corresponding value is 0, or -1 if the 84 // given object ID isn't in our map. 85 int GetRefCountForObject(const PP_Var& object); 86 int GetTrackedWithNoReferenceCountForObject(const PP_Var& object); 87 88 // Called after an instance is deleted to do var cleanup. 89 virtual void DidDeleteInstance(PP_Instance instance) = 0; 90 91 protected: 92 struct VarInfo { 93 VarInfo(); 94 VarInfo(Var* v, int input_ref_count); 95 96 scoped_refptr<Var> var; 97 98 // Explicit reference count. This value is affected by the renderer calling 99 // AddRef and Release. A nonzero value here is represented by a single 100 // reference in the host on our behalf (this reduces IPC traffic). 101 int ref_count; 102 103 // Tracked object count (see class comment above). 104 // 105 // "TrackObjectWithNoReference" might be called recursively in rare cases. 106 // For example, say the host calls a plugin function with an object as an 107 // argument, and in response, the plugin calls a host function that then 108 // calls another (or the same) plugin function with the same object. 109 // 110 // This value tracks the number of calls to TrackObjectWithNoReference so 111 // we know when we can stop tracking this object. 112 int track_with_no_reference_count; 113 }; 114 typedef base::hash_map<int32, VarInfo> VarMap; 115 116 // Specifies what should happen with the refcount when calling AddVarInternal. 117 enum AddVarRefMode { 118 ADD_VAR_TAKE_ONE_REFERENCE, 119 ADD_VAR_CREATE_WITH_NO_REFERENCE 120 }; 121 122 // Implementation of AddVar that allows the caller to specify whether the 123 // initial refcount of the added object will be 0 or 1. 124 // 125 // Overridden in the plugin proxy to do additional object tracking. 126 virtual int32 AddVarInternal(Var* var, AddVarRefMode mode); 127 128 // Convenience functions for doing lookups into the live_vars_ map. 129 VarMap::iterator GetLiveVar(int32 id); 130 VarMap::iterator GetLiveVar(const PP_Var& var); 131 VarMap::const_iterator GetLiveVar(const PP_Var& var) const; 132 133 // Returns true if the given vartype is refcounted and has associated objects 134 // (it's not POD). 135 bool IsVarTypeRefcounted(PP_VarType type) const; 136 137 // Called when AddRefVar increases a "tracked" ProxyObject's refcount from 138 // zero to one. In the plugin side of the proxy, we need to send some 139 // messages to the host. In the host side, this should never be called since 140 // there are no proxy objects. 141 virtual void TrackedObjectGettingOneRef(VarMap::const_iterator iter); 142 143 // Called when ReleaseVar decreases a object's refcount from one to zero. It 144 // may still be "tracked" (has a "track_with_no_reference_count") value. In 145 // the plugin side of the proxy, we need to tell the host that we no longer 146 // have a reference. In the host side, this should never be called since 147 // there are no proxy objects. 148 virtual void ObjectGettingZeroRef(VarMap::iterator iter); 149 150 // Called when an object may have had its refcount or 151 // track_with_no_reference_count value decreased. If the object has neither 152 // refs anymore, this will remove it and return true. Returns false if it's 153 // still alive. 154 // 155 // Overridden by the PluginVarTracker to also clean up the host info map. 156 virtual bool DeleteObjectInfoIfNecessary(VarMap::iterator iter); 157 158 VarMap live_vars_; 159 160 // Last assigned var ID. 161 int32 last_var_id_; 162 163 private: 164 // Create and return a new ArrayBufferVar size_in_bytes bytes long. This is 165 // implemented by the Host and Plugin tracker separately, so that it can be 166 // a real WebKit ArrayBuffer on the host side. 167 virtual ArrayBufferVar* CreateArrayBuffer(uint32 size_in_bytes) = 0; 168 169 DISALLOW_COPY_AND_ASSIGN(VarTracker); 170}; 171 172} // namespace ppapi 173 174#endif // PPAPI_SHARED_IMPL_VAR_TRACKER_H_ 175