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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 "base/win/windows_types.h"
     12 #endif
     13 
     14 #include <memory>
     15 #include <string>
     16 
     17 #include "build/build_config.h"
     18 #include "ipc/ipc_message.h"
     19 #include "ipc/ipc_message_support_export.h"
     20 
     21 namespace base {
     22 class WaitableEvent;
     23 }
     24 
     25 namespace IPC {
     26 
     27 class MessageReplyDeserializer;
     28 
     29 class IPC_MESSAGE_SUPPORT_EXPORT SyncMessage : public Message {
     30  public:
     31   SyncMessage(int32_t routing_id,
     32               uint32_t type,
     33               PriorityValue priority,
     34               MessageReplyDeserializer* deserializer);
     35   ~SyncMessage() override;
     36 
     37   // Call this to get a deserializer for the output parameters.
     38   // Note that this can only be called once, and the caller is responsible
     39   // for deleting the deserializer when they're done.
     40   MessageReplyDeserializer* GetReplyDeserializer();
     41 
     42   // If this message can cause the receiver to block while waiting for user
     43   // input (i.e. by calling MessageBox), then the caller needs to pump window
     44   // messages and dispatch asynchronous messages while waiting for the reply.
     45   // This call enables message pumping behavior while waiting for a reply to
     46   // this message.
     47   void EnableMessagePumping() {
     48     header()->flags |= PUMPING_MSGS_BIT;
     49   }
     50 
     51   // Indicates whether window messages should be pumped while waiting for a
     52   // reply to this message.
     53   bool ShouldPumpMessages() const {
     54     return (header()->flags & PUMPING_MSGS_BIT) != 0;
     55   }
     56 
     57   // Returns true if the message is a reply to the given request id.
     58   static bool IsMessageReplyTo(const Message& msg, int request_id);
     59 
     60   // Given a reply message, returns an iterator to the beginning of the data
     61   // (i.e. skips over the synchronous specific data).
     62   static base::PickleIterator GetDataIterator(const Message* msg);
     63 
     64   // Given a synchronous message (or its reply), returns its id.
     65   static int GetMessageId(const Message& msg);
     66 
     67   // Generates a reply message to the given message.
     68   static Message* GenerateReply(const Message* msg);
     69 
     70  private:
     71   struct SyncHeader {
     72     // unique ID (unique per sender)
     73     int message_id;
     74   };
     75 
     76   static bool ReadSyncHeader(const Message& msg, SyncHeader* header);
     77   static bool WriteSyncHeader(Message* msg, const SyncHeader& header);
     78 
     79   std::unique_ptr<MessageReplyDeserializer> deserializer_;
     80 };
     81 
     82 // Used to deserialize parameters from a reply to a synchronous message
     83 class IPC_MESSAGE_SUPPORT_EXPORT MessageReplyDeserializer {
     84  public:
     85   virtual ~MessageReplyDeserializer() {}
     86   bool SerializeOutputParameters(const Message& msg);
     87  private:
     88   // Derived classes need to implement this, using the given iterator (which
     89   // is skipped past the header for synchronous messages).
     90   virtual bool SerializeOutputParameters(const Message& msg,
     91                                          base::PickleIterator iter) = 0;
     92 };
     93 
     94 // When sending a synchronous message, this structure contains an object
     95 // that knows how to deserialize the response.
     96 struct PendingSyncMsg {
     97   PendingSyncMsg(int id, MessageReplyDeserializer* d, base::WaitableEvent* e)
     98       : id(id), deserializer(d), done_event(e), send_result(false) {}
     99 
    100   int id;
    101   MessageReplyDeserializer* deserializer;
    102   base::WaitableEvent* done_event;
    103   bool send_result;
    104 };
    105 
    106 }  // namespace IPC
    107 
    108 #endif  // IPC_IPC_SYNC_MESSAGE_H_
    109