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      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 #include "ppapi/proxy/plugin_var_serialization_rules.h"
      6 
      7 #include "base/logging.h"
      8 #include "ppapi/proxy/plugin_dispatcher.h"
      9 #include "ppapi/proxy/plugin_globals.h"
     10 #include "ppapi/proxy/plugin_resource_tracker.h"
     11 #include "ppapi/proxy/plugin_var_tracker.h"
     12 #include "ppapi/shared_impl/ppapi_globals.h"
     13 #include "ppapi/shared_impl/var.h"
     14 
     15 namespace ppapi {
     16 namespace proxy {
     17 
     18 PluginVarSerializationRules::PluginVarSerializationRules(
     19     const base::WeakPtr<PluginDispatcher>& dispatcher)
     20     : var_tracker_(PluginGlobals::Get()->plugin_var_tracker()),
     21       dispatcher_(dispatcher) {
     22 }
     23 
     24 PluginVarSerializationRules::~PluginVarSerializationRules() {
     25 }
     26 
     27 PP_Var PluginVarSerializationRules::SendCallerOwned(const PP_Var& var) {
     28   // Objects need special translations to get the IDs valid in the host.
     29   if (var.type == PP_VARTYPE_OBJECT)
     30     return var_tracker_->GetHostObject(var);
     31   return var;
     32 }
     33 
     34 PP_Var PluginVarSerializationRules::BeginReceiveCallerOwned(const PP_Var& var) {
     35   if (var.type == PP_VARTYPE_OBJECT) {
     36     return dispatcher_.get() ? var_tracker_->TrackObjectWithNoReference(
     37                                    var, dispatcher_.get())
     38                              : PP_MakeUndefined();
     39   }
     40 
     41   return var;
     42 }
     43 
     44 void PluginVarSerializationRules::EndReceiveCallerOwned(const PP_Var& var) {
     45   if (var.type == PP_VARTYPE_OBJECT) {
     46     var_tracker_->StopTrackingObjectWithNoReference(var);
     47   } else if (var.type >= PP_VARTYPE_STRING) {
     48     // Release our reference to the local Var.
     49     var_tracker_->ReleaseVar(var);
     50   }
     51 }
     52 
     53 PP_Var PluginVarSerializationRules::ReceivePassRef(const PP_Var& var) {
     54   // Overview of sending an object with "pass ref" from the browser to the
     55   // plugin:
     56   //                                  Example 1             Example 2
     57   //                               Plugin   Browser      Plugin   Browser
     58   // Before send                      3        2            0        1
     59   // Browser calls BeginSendPassRef   3        2            0        1
     60   // Plugin calls ReceivePassRef      4        1            1        1
     61   // Browser calls EndSendPassRef     4        1            1        1
     62   //
     63   // In example 1 before the send, the plugin has 3 refs which are represented
     64   // as one ref in the browser (since the plugin only tells the browser when
     65   // it's refcount goes from 1 -> 0). The initial state is that the browser
     66   // plugin code started to return a value, which means it gets another ref
     67   // on behalf of the caller. This needs to be transferred to the plugin and
     68   // folded in to its set of refs it maintains (with one ref representing all
     69   // of them in the browser).
     70   if (var.type == PP_VARTYPE_OBJECT) {
     71     return dispatcher_.get()
     72                ? var_tracker_->ReceiveObjectPassRef(var, dispatcher_.get())
     73                : PP_MakeUndefined();
     74   }
     75 
     76   // Other types are unchanged.
     77   return var;
     78 }
     79 
     80 PP_Var PluginVarSerializationRules::BeginSendPassRef(const PP_Var& var) {
     81   // Overview of sending an object with "pass ref" from the plugin to the
     82   // browser:
     83   //                                  Example 1             Example 2
     84   //                               Plugin   Browser      Plugin   Browser
     85   // Before send                      3        1            1        1
     86   // Plugin calls BeginSendPassRef    3        1            1        1
     87   // Browser calls ReceivePassRef     3        2            1        2
     88   // Plugin calls EndSendPassRef      2        2            0        1
     89   //
     90   // The plugin maintains one ref count in the browser on behalf of the
     91   // entire ref count in the plugin. When the plugin refcount goes to 0, it
     92   // will call the browser to deref the object. This is why in example 2
     93   // transferring the object ref to the browser involves no net change in the
     94   // browser's refcount.
     95 
     96   // Objects need special translations to get the IDs valid in the host.
     97   if (var.type == PP_VARTYPE_OBJECT)
     98     return var_tracker_->GetHostObject(var);
     99   return var;
    100 }
    101 
    102 void PluginVarSerializationRules::EndSendPassRef(const PP_Var& var) {
    103   // See BeginSendPassRef for an example of why we release our ref here.
    104   // The var we have in our inner class has been converted to a host object
    105   // by BeginSendPassRef. This means it's not a normal var valid in the plugin,
    106   // so we need to use the special ReleaseHostObject.
    107   if (var.type == PP_VARTYPE_OBJECT) {
    108     if (dispatcher_.get())
    109       var_tracker_->ReleaseHostObject(dispatcher_.get(), var);
    110   } else if (var.type >= PP_VARTYPE_STRING) {
    111     var_tracker_->ReleaseVar(var);
    112   }
    113 }
    114 
    115 void PluginVarSerializationRules::ReleaseObjectRef(const PP_Var& var) {
    116   var_tracker_->ReleaseVar(var);
    117 }
    118 
    119 }  // namespace proxy
    120 }  // namespace ppapi
    121