First pass at making the proxy handle multiple renderers. This associates the...

ppapi/proxy/plugin_var_tracker.h

 // Copyright (c) 2010 The Chromium 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 PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_
 #define PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_
 
 #include <map>
 #include <string>
 
+#include "ipc/ipc_channel.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_var.h"
 
 struct PPB_Var;
 
+template<typename T> struct DefaultSingletonTraits;
+
 namespace pp {
 namespace proxy {
 
-class PluginDispatcher;
-
-// Tracks live strings and objects in the plugin process. We maintain our own
-// reference count for these objects. In the case of JS objects, we maintain
-// a single ref in the renderer process whenever we have a nonzero refcount
-// in the plugin process. This allows AddRef and Release to not initiate too
-// much IPC chat.
+// Tracks live strings and objects in the plugin process.
+//
+// This object maintains its own object IDs that are used by the plugin. These
+// IDs can be mapped to the renderer that created them, and that renderer's ID.
+// This way, we can maintain multiple renderers each giving us objects, and the
+// plugin can work with them using a uniform set of unique IDs.
+//
+// We maintain our own reference count for objects.  a single ref in the
+// renderer process whenever we have a nonzero refcount in the plugin process.
+// This allows AddRef and Release to not initiate too much IPC chat.
+//
+// In addition to the local reference count, we also maintain "tracked objects"
+// which are objects that the plugin is aware of, but doesn't hold a reference
+// to. This will happen when the plugin is passed an object as an argument from
+// the host (renderer) but where a reference is not passed.
 class PluginVarTracker {
  public:
-  // You must call Init() after creation to set up the correct interfaces. We
-  // do this to avoid having to depend on the dispatcher in the constructor,
-  // which is probably just being created from our constructor.
-  PluginVarTracker(PluginDispatcher* dispatcher);
+  typedef int64_t VarID;
 
-  ~PluginVarTracker();
+  // This uses the PluginDispatcher to identify the source of vars so that
+  // the proper messages can be sent back. However, since all we need is the
+  // ability to send messages, we can always use the Sender base class of
+  // Dispatcher in this class, which makes it easy to unit test.
+  typedef IPC::Channel::Sender Sender;
 
-  // Must be called after construction.
-  void Init();
+  // Returns the global var tracker for the plugin object.
+  static PluginVarTracker* GetInstance();
 
   // Allocates a string and returns the ID of it. The refcount will be 1.
-  int64_t MakeString(const std::string& str);
-  int64_t MakeString(const char* str, uint32_t len);
+  VarID MakeString(const std::string& str);
+  VarID MakeString(const char* str, uint32_t len);
 
   // Returns the string associated with the given string var. The var must be
   // of type string and must be valid or this function will crash.
-  std::string GetString(const PP_Var& var) const;
+  std::string GetString(const PP_Var& plugin_var) const;
 
   // Returns a pointer to the given string if it exists, or NULL if the var
   // isn't a string var.
-  const std::string* GetExistingString(const PP_Var& var) const;
+  const std::string* GetExistingString(const PP_Var& plugin_var) const;
 
-  void AddRef(const PP_Var& var);
-  void Release(const PP_Var& var);
+  void AddRef(const PP_Var& plugin_var);
+  void Release(const PP_Var& plugin_var);
 
   // Manages tracking for receiving a VARTYPE_OBJECT from the remote side
   // (either the plugin or the renderer) that has already had its reference
   // count incremented on behalf of the caller.
-  void ReceiveObjectPassRef(const PP_Var& var);
+  PP_Var ReceiveObjectPassRef(const PP_Var& var, Sender* channel);
+
+  PP_Var TrackObjectWithNoReference(const PP_Var& host_var,
+                                    Sender* channel);
+  void StopTrackingObjectWithNoReference(const PP_Var& plugin_var);
+
+  // Returns the host var for the corresponding plugin object var. The object
+  // should be a VARTYPE_OBJECT
+  PP_Var GetHostObject(const PP_Var& plugin_object) const;
+
+  // Retrieves the internal reference counts for testing. Returns 0 if we
+  // know about the object but the corresponding value is 0, or -1 if the
+  // given object ID isn't in our map.
+  int GetRefCountForObject(const PP_Var& plugin_object);
+  int GetTrackedWithNoReferenceCountForObject(const PP_Var& plugin_object);
 
  private:
+  friend struct DefaultSingletonTraits<PluginVarTracker>;
+
+  // Represents a var as received from the host.
+  struct HostVar {
+    HostVar(Sender* s, int64_t i);
+
+    bool operator<(const HostVar& other) const;
+
+    // The host that sent us this object. This is used so we know how to send
+    // back requests on this object.
+    Sender* channel;
+
+    // The object ID that the host generated to identify the object. This is
+    // unique only within that host: different hosts could give us different
+    // objects with the same ID.
+    VarID host_object_id;
+  };
+
+  // The information associated with a var object in the plugin.
+  struct PluginVarInfo {
+    PluginVarInfo(const HostVar& host_var);
+
+    // Maps back to the original var in the host.
+    HostVar host_var;
+
+    // Explicit reference count. This value is affected by the renderer calling
+    // AddRef and Release. A nonzero value here is represented by a single
+    // reference in the host on our behalf (this reduces IPC traffic).
+    int32_t ref_count;
+
+    // Tracked object count (see class comment above).
+    //
+    // "TrackObjectWithNoReference" might be called recursively in rare cases.
+    // For example, say the host calls a plugin function with an object as an
+    // argument, and in response, the plugin calls a host function that then
+    // calls another (or the same) plugin function with the same object.
+    //
+    // This value tracks the number of calls to TrackObjectWithNoReference so
+    // we know when we can stop tracking this object.
+    int32_t track_with_no_reference_count;
+  };
+
+  typedef std::map<int64_t, PluginVarInfo> PluginVarInfoMap;
+
+  PluginVarTracker();
+  ~PluginVarTracker();
+
   // Sends an addref or release message to the browser for the given object ID.
-  void SendAddRefObjectMsg(int64_t id);
-  void SendReleaseObjectMsg(int64_t id);
+  void SendAddRefObjectMsg(const HostVar& host_var);
+  void SendReleaseObjectMsg(const HostVar& host_var);
 
-  PluginDispatcher* dispatcher_;
+  PluginVarInfoMap::iterator FindOrMakePluginVarFromHostVar(
+      const PP_Var& var,
+      Sender* channel);
 
-  // Tracks object references to the reference count of that object on the
-  // plugin side.
-  typedef std::map<int64_t, int> ObjectRefCount;
-  ObjectRefCount object_ref_count_;
+  // Checks the reference counds of the given plugin var info and removes the
+  // tracking information if necessary. We're done with the object when its
+  // explicit reference count and its "tracked with no reference" count both
+  // reach zero.
+  void DeletePluginVarInfoIfNecessary(PluginVarInfoMap::iterator iter);
+
+  // Tracks all information about plugin vars.
+  PluginVarInfoMap plugin_var_info_;
+
+  // Maps host vars to plugin vars. This allows us to know if we've previously
+  // seen a host var and re-use the information.
+  typedef std::map<HostVar, VarID> HostVarToPluginVarMap;
+  HostVarToPluginVarMap host_var_to_plugin_var_;
+
+  // The last plugin object ID we've handed out. This must be unique for the
+  // process.
+  VarID last_plugin_object_id_;
 };
 
 }  // namespace proxy
 }  // namespace pp
 
 #endif  // PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_