ppapi/host/resource_message_handler.h

   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_