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
15namespace ppapi {
16namespace proxy {
17
18PluginVarSerializationRules::PluginVarSerializationRules(
19    const base::WeakPtr<PluginDispatcher>& dispatcher)
20    : var_tracker_(PluginGlobals::Get()->plugin_var_tracker()),
21      dispatcher_(dispatcher) {
22}
23
24PluginVarSerializationRules::~PluginVarSerializationRules() {
25}
26
27PP_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
34PP_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
44void 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
53PP_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
80PP_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
102void 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
115void PluginVarSerializationRules::ReleaseObjectRef(const PP_Var& var) {
116  var_tracker_->ReleaseVar(var);
117}
118
119}  // namespace proxy
120}  // namespace ppapi
121