ipc/ipc_sync_message.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 IPC_IPC_SYNC_MESSAGE_H_
   6 #define IPC_IPC_SYNC_MESSAGE_H_
   7
   8 #if defined(OS_WIN)
   9 #include <windows.h>
  10 #endif
  11 #include <string>
  12 #include "base/basictypes.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "ipc/ipc_message.h"
  15
  16 namespace base {
  17 class WaitableEvent;
  18 }
  19
  20 namespace IPC {
  21
  22 class MessageReplyDeserializer;
  23
  24 class IPC_EXPORT SyncMessage : public Message {
  25  public:
  26   SyncMessage(int32 routing_id, uint32 type, PriorityValue priority,
  27               MessageReplyDeserializer* deserializer);
  28   ~SyncMessage() override;
  29
  30   // Call this to get a deserializer for the output parameters.
  31   // Note that this can only be called once, and the caller is responsible
  32   // for deleting the deserializer when they're done.
  33   MessageReplyDeserializer* GetReplyDeserializer();
  34
  35   // If this message can cause the receiver to block while waiting for user
  36   // input (i.e. by calling MessageBox), then the caller needs to pump window
  37   // messages and dispatch asynchronous messages while waiting for the reply.
  38   // If this event is passed in, then window messages will start being pumped
  39   // when it's set.  Note that this behavior will continue even if the event is
  40   // later reset.  The event must be valid until after the Send call returns.
  41   void set_pump_messages_event(base::WaitableEvent* event) {
  42     pump_messages_event_ = event;
  43     if (event) {
  44       header()->flags |= PUMPING_MSGS_BIT;
  45     } else {
  46       header()->flags &= ~PUMPING_MSGS_BIT;
  47     }
  48   }
  49
  50   // Call this if you always want to pump messages.  You can call this method
  51   // or set_pump_messages_event but not both.
  52   void EnableMessagePumping();
  53
  54   base::WaitableEvent* pump_messages_event() const {
  55     return pump_messages_event_;
  56   }
  57
  58   // Returns true if the message is a reply to the given request id.
  59   static bool IsMessageReplyTo(const Message& msg, int request_id);
  60
  61   // Given a reply message, returns an iterator to the beginning of the data
  62   // (i.e. skips over the synchronous specific data).
  63   static base::PickleIterator GetDataIterator(const Message* msg);
  64
  65   // Given a synchronous message (or its reply), returns its id.
  66   static int GetMessageId(const Message& msg);
  67
  68   // Generates a reply message to the given message.
  69   static Message* GenerateReply(const Message* msg);
  70
  71  private:
  72   struct SyncHeader {
  73     // unique ID (unique per sender)
  74     int message_id;
  75   };
  76
  77   static bool ReadSyncHeader(const Message& msg, SyncHeader* header);
  78   static bool WriteSyncHeader(Message* msg, const SyncHeader& header);
  79
  80   scoped_ptr<MessageReplyDeserializer> deserializer_;
  81   base::WaitableEvent* pump_messages_event_;
  82 };
  83
  84 // Used to deserialize parameters from a reply to a synchronous message
  85 class IPC_EXPORT MessageReplyDeserializer {
  86  public:
  87   virtual ~MessageReplyDeserializer() {}
  88   bool SerializeOutputParameters(const Message& msg);
  89  private:
  90   // Derived classes need to implement this, using the given iterator (which
  91   // is skipped past the header for synchronous messages).
  92   virtual bool SerializeOutputParameters(const Message& msg,
  93                                          base::PickleIterator iter) = 0;
  94 };
  95
  96 // When sending a synchronous message, this structure contains an object
  97 // that knows how to deserialize the response.
  98 struct PendingSyncMsg {
  99   PendingSyncMsg(int id,
 100                  MessageReplyDeserializer* d,
 101                  base::WaitableEvent* e)
 102       : id(id), deserializer(d), done_event(e), send_result(false) { }
 103   int id;
 104   MessageReplyDeserializer* deserializer;
 105   base::WaitableEvent* done_event;
 106   bool send_result;
 107 };
 108
 109 }  // namespace IPC
 110
 111 #endif  // IPC_IPC_SYNC_MESSAGE_H_