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 #include <stdint.h>
   9 #if defined(OS_WIN)
  10 #include <windows.h>
  11 #endif
  12 #include <string>
  13 #include "base/basictypes.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "ipc/ipc_message.h"
  16
  17 namespace base {
  18 class WaitableEvent;
  19 }
  20
  21 namespace IPC {
  22
  23 class MessageReplyDeserializer;
  24
  25 class IPC_EXPORT SyncMessage : public Message {
  26  public:
  27   SyncMessage(int32_t routing_id,
  28               uint32_t type,
  29               PriorityValue priority,
  30               MessageReplyDeserializer* deserializer);
  31   ~SyncMessage() override;
  32
  33   // Call this to get a deserializer for the output parameters.
  34   // Note that this can only be called once, and the caller is responsible
  35   // for deleting the deserializer when they're done.
  36   MessageReplyDeserializer* GetReplyDeserializer();
  37
  38   // If this message can cause the receiver to block while waiting for user
  39   // input (i.e. by calling MessageBox), then the caller needs to pump window
  40   // messages and dispatch asynchronous messages while waiting for the reply.
  41   // If this event is passed in, then window messages will start being pumped
  42   // when it's set.  Note that this behavior will continue even if the event is
  43   // later reset.  The event must be valid until after the Send call returns.
  44   void set_pump_messages_event(base::WaitableEvent* event) {
  45     pump_messages_event_ = event;
  46     if (event) {
  47       header()->flags |= PUMPING_MSGS_BIT;
  48     } else {
  49       header()->flags &= ~PUMPING_MSGS_BIT;
  50     }
  51   }
  52
  53   // Call this if you always want to pump messages.  You can call this method
  54   // or set_pump_messages_event but not both.
  55   void EnableMessagePumping();
  56
  57   base::WaitableEvent* pump_messages_event() const {
  58     return pump_messages_event_;
  59   }
  60
  61   // Returns true if the message is a reply to the given request id.
  62   static bool IsMessageReplyTo(const Message& msg, int request_id);
  63
  64   // Given a reply message, returns an iterator to the beginning of the data
  65   // (i.e. skips over the synchronous specific data).
  66   static base::PickleIterator GetDataIterator(const Message* msg);
  67
  68   // Given a synchronous message (or its reply), returns its id.
  69   static int GetMessageId(const Message& msg);
  70
  71   // Generates a reply message to the given message.
  72   static Message* GenerateReply(const Message* msg);
  73
  74  private:
  75   struct SyncHeader {
  76     // unique ID (unique per sender)
  77     int message_id;
  78   };
  79
  80   static bool ReadSyncHeader(const Message& msg, SyncHeader* header);
  81   static bool WriteSyncHeader(Message* msg, const SyncHeader& header);
  82
  83   scoped_ptr<MessageReplyDeserializer> deserializer_;
  84   base::WaitableEvent* pump_messages_event_;
  85 };
  86
  87 // Used to deserialize parameters from a reply to a synchronous message
  88 class IPC_EXPORT MessageReplyDeserializer {
  89  public:
  90   virtual ~MessageReplyDeserializer() {}
  91   bool SerializeOutputParameters(const Message& msg);
  92  private:
  93   // Derived classes need to implement this, using the given iterator (which
  94   // is skipped past the header for synchronous messages).
  95   virtual bool SerializeOutputParameters(const Message& msg,
  96                                          base::PickleIterator iter) = 0;
  97 };
  98
  99 // When sending a synchronous message, this structure contains an object
 100 // that knows how to deserialize the response.
 101 struct PendingSyncMsg {
 102   PendingSyncMsg(int id,
 103                  MessageReplyDeserializer* d,
 104                  base::WaitableEvent* e)
 105       : id(id), deserializer(d), done_event(e), send_result(false) { }
 106   int id;
 107   MessageReplyDeserializer* deserializer;
 108   base::WaitableEvent* done_event;
 109   bool send_result;
 110 };
 111
 112 }  // namespace IPC
 113
 114 #endif  // IPC_IPC_SYNC_MESSAGE_H_