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      1 // Copyright 2014 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 MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
      6 #define MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
      7 
      8 #include <vector>
      9 
     10 #include "mojo/public/cpp/bindings/lib/message_internal.h"
     11 #include "mojo/public/cpp/environment/logging.h"
     12 
     13 namespace mojo {
     14 
     15 // Message is a holder for the data and handles to be sent over a MessagePipe.
     16 // Message owns its data and handles, but a consumer of Message is free to
     17 // mutate the data and handles. The message's data is comprised of a header
     18 // followed by payload.
     19 class Message {
     20  public:
     21   Message();
     22   ~Message();
     23 
     24   // These may only be called on a newly created Message object.
     25   void AllocUninitializedData(uint32_t num_bytes);
     26   void AdoptData(uint32_t num_bytes, internal::MessageData* data);
     27 
     28   // Swaps data and handles between this Message and another.
     29   void Swap(Message* other);
     30 
     31   uint32_t data_num_bytes() const { return data_num_bytes_; }
     32 
     33   // Access the raw bytes of the message.
     34   const uint8_t* data() const { return
     35     reinterpret_cast<const uint8_t*>(data_);
     36   }
     37   uint8_t* mutable_data() { return reinterpret_cast<uint8_t*>(data_); }
     38 
     39   // Access the header.
     40   const internal::MessageHeader* header() const { return &data_->header; }
     41 
     42   uint32_t name() const { return data_->header.name; }
     43   bool has_flag(uint32_t flag) const { return !!(data_->header.flags & flag); }
     44 
     45   // Access the request_id field (if present).
     46   bool has_request_id() const { return data_->header.num_fields >= 3; }
     47   uint64_t request_id() const {
     48     MOJO_DCHECK(has_request_id());
     49     return static_cast<const internal::MessageHeaderWithRequestID*>(
     50         &data_->header)->request_id;
     51   }
     52   void set_request_id(uint64_t request_id) {
     53     MOJO_DCHECK(has_request_id());
     54     static_cast<internal::MessageHeaderWithRequestID*>(&data_->header)->
     55         request_id = request_id;
     56   }
     57 
     58   // Access the payload.
     59   const uint8_t* payload() const {
     60     return reinterpret_cast<const uint8_t*>(data_) + data_->header.num_bytes;
     61   }
     62   uint8_t* mutable_payload() {
     63     return reinterpret_cast<uint8_t*>(data_) + data_->header.num_bytes;
     64   }
     65   uint32_t payload_num_bytes() const {
     66     MOJO_DCHECK(data_num_bytes_ >= data_->header.num_bytes);
     67     return data_num_bytes_ - data_->header.num_bytes;
     68   }
     69 
     70   // Access the handles.
     71   const std::vector<Handle>* handles() const { return &handles_; }
     72   std::vector<Handle>* mutable_handles() { return &handles_; }
     73 
     74  private:
     75   uint32_t data_num_bytes_;
     76   internal::MessageData* data_;  // Heap-allocated using malloc.
     77   std::vector<Handle> handles_;
     78 
     79   MOJO_DISALLOW_COPY_AND_ASSIGN(Message);
     80 };
     81 
     82 class MessageReceiver {
     83  public:
     84   virtual ~MessageReceiver() {}
     85 
     86   // The receiver may mutate the given message.  Returns true if the message
     87   // was accepted and false otherwise, indicating that the message was invalid
     88   // or malformed.
     89   virtual bool Accept(Message* message) MOJO_WARN_UNUSED_RESULT = 0;
     90 };
     91 
     92 class MessageReceiverWithResponder : public MessageReceiver {
     93  public:
     94   virtual ~MessageReceiverWithResponder() {}
     95 
     96   // A variant on Accept that registers a MessageReceiver (known as the
     97   // responder) to handle the response message generated from the given
     98   // message. The responder's Accept method may be called during
     99   // AcceptWithResponder or some time after its return.
    100   //
    101   // NOTE: Upon returning true, AcceptWithResponder assumes ownership of
    102   // |responder| and will delete it after calling |responder->Accept| or upon
    103   // its own destruction.
    104   //
    105   virtual bool AcceptWithResponder(
    106       Message* message, MessageReceiver* responder) MOJO_WARN_UNUSED_RESULT = 0;
    107 };
    108 
    109 // Read a single message from the pipe and dispatch to the given receiver.  The
    110 // receiver may be null, in which case the message is simply discarded.
    111 // Returns MOJO_RESULT_SHOULD_WAIT if the caller should wait on the handle to
    112 // become readable. Returns MOJO_RESULT_OK if a message was dispatched and
    113 // otherwise returns an error code if something went wrong.
    114 //
    115 // NOTE: The message hasn't been validated and may be malformed!
    116 MojoResult ReadAndDispatchMessage(MessagePipeHandle handle,
    117                                   MessageReceiver* receiver,
    118                                   bool* receiver_result);
    119 
    120 }  // namespace mojo
    121 
    122 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
    123