mojo/public/cpp/bindings/message.h

   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_