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.
5 #ifndef PPAPI_HOST_RESOURCE_MESSAGE_FILTER_H_
6 #define PPAPI_HOST_RESOURCE_MESSAGE_FILTER_H_
8 #include "base/memory/ref_counted.h"
9 #include "ppapi/c/pp_stdint.h"
10 #include "ppapi/host/host_message_context.h"
11 #include "ppapi/host/ppapi_host_export.h"
12 #include "ppapi/host/resource_message_handler.h"
15 class MessageLoopProxy;
28 // This is the base class of resource message filters that can handle resource
29 // messages on another thread. ResourceHosts can handle most messages
30 // directly, but if they need to handle something on a different thread it is
31 // inconvenient. This class makes handling that case easier. This class is
32 // similar to a BrowserMessageFilter but for resource messages. Note that the
33 // liftetime of a ResourceHost is managed by a PpapiHost and may be destroyed
34 // before or while your message is being processed on another thread.
35 // If this is the case, the message handler will always be called but a reply
36 // may not be sent back to the host.
38 // To handle a resource message on another thread you should implement a
39 // subclass as follows:
40 // class MyMessageFilter : public ResourceMessageFilter {
42 // virtual scoped_refptr<base::TaskRunner> OverrideTaskRunnerForMessage(
43 // const IPC::Message& message) OVERRIDE {
44 // if (message.type() == MyMessage::ID)
45 // return BrowserThread::GetMessageLoopProxyForThread(BrowserThread::UI);
49 // virtual int32_t OnResourceMessageReceived(
50 // const IPC::Message& msg,
51 // HostMessageContext* context) OVERRIDE {
52 // IPC_BEGIN_MESSAGE_MAP(MyMessageFilter, msg)
53 // PPAPI_DISPATCH_HOST_RESOURCE_CALL(MyMessage, OnMyMessage)
54 // IPC_END_MESSAGE_MAP()
55 // return PP_ERROR_FAILED;
59 // int32_t OnMyMessage(ppapi::host::HostMessageContext* context, ...) {
60 // // Will be run on the UI thread.
64 // The filter should then be added in the resource host using:
65 // AddFilter(make_scoped_refptr(new MyMessageFilter));
66 class PPAPI_HOST_EXPORT ResourceMessageFilter
67 : public ResourceMessageHandler,
68 public base::RefCountedThreadSafe<ResourceMessageFilter> {
70 // This object must be constructed on the same thread that a reply message
71 // should be sent, i.e. the IO thread when constructed in the browser process
72 // or the main thread when constructed in the renderer process. Since
73 // ResourceMessageFilters are usually constructed in the constructor of the
74 // owning ResourceHost, this will almost always be the case anyway.
75 ResourceMessageFilter();
76 // Test constructor. Allows you to specify the message loop which will be used
77 // to dispatch replies on.
78 ResourceMessageFilter(
79 scoped_refptr<base::MessageLoopProxy> reply_thread_message_loop_proxy);
81 // Called when a filter is added to a ResourceHost.
82 void OnFilterAdded(ResourceHost* resource_host);
83 // Called when a filter is removed from a ResourceHost.
84 void OnFilterDestroyed();
86 // This will dispatch the message handler on the target thread. It returns
87 // true if the message was handled by this filter and false otherwise.
88 virtual bool HandleMessage(const IPC::Message& msg,
89 HostMessageContext* context) OVERRIDE;
91 // This can be called from any thread.
92 virtual void SendReply(const ReplyMessageContext& context,
93 const IPC::Message& msg) OVERRIDE;
96 friend class base::RefCountedThreadSafe<ResourceMessageFilter>;
97 virtual ~ResourceMessageFilter();
99 // If you want the message to be handled on another thread, return a non-null
100 // task runner which will target tasks accordingly.
101 virtual scoped_refptr<base::TaskRunner> OverrideTaskRunnerForMessage(
102 const IPC::Message& message);
105 // This method is posted to the target thread and runs the message handler.
106 void DispatchMessage(const IPC::Message& msg,
107 HostMessageContext context);
109 // Message loop to send resource message replies on. This will be the message
110 // loop proxy of the IO thread for the browser process or the main thread for
111 // the renderer process.
112 scoped_refptr<base::MessageLoopProxy> reply_thread_message_loop_proxy_;
114 // Non-owning pointer to the resource host owning this filter. Should only be
115 // accessed from the thread which sends messages to the plugin resource (i.e.
116 // the IO thread for the browser process or the main thread for the renderer).
117 // This will be NULL upon creation of the filter and is set to the owning
118 // ResourceHost when |OnFilterAdded| is called. When the owning ResourceHost
119 // is destroyed, |OnFilterDestroyed| is called and this will be set to NULL.
120 ResourceHost* resource_host_;
122 DISALLOW_COPY_AND_ASSIGN(ResourceMessageFilter);
128 #endif // PPAPI_HOST_RESOURCE_MESSAGE_FILTER_H_