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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 IPC_IPC_SYNC_MESSAGE_H_
      6 #define IPC_IPC_SYNC_MESSAGE_H_
      7 
      8 #include <stdint.h>
      9 
     10 #if defined(OS_WIN)
     11 #include <windows.h>
     12 #endif
     13 
     14 #include <memory>
     15 #include <string>
     16 
     17 #include "build/build_config.h"
     18 #include "ipc/ipc_message.h"
     19 
     20 namespace IPC {
     21 
     22 class MessageReplyDeserializer;
     23 class MojoEvent;
     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   // This call enables message pumping behavior while waiting for a reply to
     42   // this message.
     43   void EnableMessagePumping() {
     44     header()->flags |= PUMPING_MSGS_BIT;
     45   }
     46 
     47   // Indicates whether window messages should be pumped while waiting for a
     48   // reply to this message.
     49   bool ShouldPumpMessages() const {
     50     return (header()->flags & PUMPING_MSGS_BIT) != 0;
     51   }
     52 
     53   // Returns true if the message is a reply to the given request id.
     54   static bool IsMessageReplyTo(const Message& msg, int request_id);
     55 
     56   // Given a reply message, returns an iterator to the beginning of the data
     57   // (i.e. skips over the synchronous specific data).
     58   static base::PickleIterator GetDataIterator(const Message* msg);
     59 
     60   // Given a synchronous message (or its reply), returns its id.
     61   static int GetMessageId(const Message& msg);
     62 
     63   // Generates a reply message to the given message.
     64   static Message* GenerateReply(const Message* msg);
     65 
     66  private:
     67   struct SyncHeader {
     68     // unique ID (unique per sender)
     69     int message_id;
     70   };
     71 
     72   static bool ReadSyncHeader(const Message& msg, SyncHeader* header);
     73   static bool WriteSyncHeader(Message* msg, const SyncHeader& header);
     74 
     75   std::unique_ptr<MessageReplyDeserializer> deserializer_;
     76 };
     77 
     78 // Used to deserialize parameters from a reply to a synchronous message
     79 class IPC_EXPORT MessageReplyDeserializer {
     80  public:
     81   virtual ~MessageReplyDeserializer() {}
     82   bool SerializeOutputParameters(const Message& msg);
     83  private:
     84   // Derived classes need to implement this, using the given iterator (which
     85   // is skipped past the header for synchronous messages).
     86   virtual bool SerializeOutputParameters(const Message& msg,
     87                                          base::PickleIterator iter) = 0;
     88 };
     89 
     90 // When sending a synchronous message, this structure contains an object
     91 // that knows how to deserialize the response.
     92 struct PendingSyncMsg {
     93   PendingSyncMsg(int id, MessageReplyDeserializer* d, MojoEvent* e)
     94       : id(id), deserializer(d), done_event(e), send_result(false) { }
     95 
     96   int id;
     97   MessageReplyDeserializer* deserializer;
     98   MojoEvent* done_event;
     99   bool send_result;
    100 };
    101 
    102 }  // namespace IPC
    103 
    104 #endif  // IPC_IPC_SYNC_MESSAGE_H_
    105