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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 #ifndef PPAPI_HOST_RESOURCE_MESSAGE_HANDLER_H_
      6 #define PPAPI_HOST_RESOURCE_MESSAGE_HANDLER_H_
      7 
      8 #include "base/basictypes.h"
      9 #include "ppapi/c/pp_stdint.h"
     10 #include "ppapi/host/ppapi_host_export.h"
     11 
     12 namespace IPC {
     13 class Message;
     14 }
     15 
     16 namespace ppapi {
     17 namespace host {
     18 
     19 struct HostMessageContext;
     20 struct ReplyMessageContext;
     21 
     22 // This is the base class of classes that can handle resource messages. It
     23 // mainly exists at present to share code for checking replies to resource
     24 // messages are valid.
     25 class PPAPI_HOST_EXPORT ResourceMessageHandler {
     26  public:
     27   ResourceMessageHandler();
     28   virtual ~ResourceMessageHandler();
     29 
     30   // Called when this handler should handle a particular message. This should
     31   // call into the the message handler implemented by subclasses (i.e.
     32   // |OnResourceMessageReceived|) and perform any additional work necessary to
     33   // handle the message (e.g. checking resource replies are valid). True is
     34   // returned if the message is handled and false otherwise.
     35   virtual bool HandleMessage(const IPC::Message& msg,
     36                              HostMessageContext* context) = 0;
     37 
     38   // Send a resource reply message.
     39   virtual void SendReply(const ReplyMessageContext& context,
     40                          const IPC::Message& msg) = 0;
     41 
     42  protected:
     43   // Runs the message handler and checks that a reply was sent if necessary.
     44   void RunMessageHandlerAndReply(const IPC::Message& msg,
     45                                  HostMessageContext* context);
     46 
     47   // Handles messages associated with a given resource object. If the flags
     48   // indicate that a response is required, the return value of this function
     49   // will be sent as a resource message "response" along with the message
     50   // specified in the reply of the context.
     51   //
     52   // You can do a response asynchronously by returning PP_OK_COMPLETIONPENDING.
     53   // This will cause the reply to be skipped, and the class implementing this
     54   // function will take responsibility for issuing the callback. The callback
     55   // can be issued inside OnResourceMessageReceived before it returns, or at
     56   // a future time.
     57   //
     58   // If you don't have a particular reply message, you can just ignore
     59   // the reply in the message context. However, if you have a reply more than
     60   // just the int32_t result code, set the reply to be the message of your
     61   // choosing.
     62   //
     63   // The default implementation just returns PP_ERROR_NOTSUPPORTED.
     64   virtual int32_t OnResourceMessageReceived(const IPC::Message& msg,
     65                                             HostMessageContext* context);
     66 
     67  private:
     68   DISALLOW_COPY_AND_ASSIGN(ResourceMessageHandler);
     69 };
     70 
     71 }  // namespace host
     72 }  // namespace ppapi
     73 
     74 #endif  // PPAPI_HOST_RESOURCE_MESSAGE_HANDLER_H_
     75