Mojo cpp bindings: validation logic for incoming messages

mojo/public/cpp/bindings/message.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 
 #include <assert.h>
 
 #include <vector>
@@ skipping 45 matching lines @@
         request_id = request_id;
   }
 
   // Access the payload.
   const uint8_t* payload() const {
     return reinterpret_cast<const uint8_t*>(data_) + data_->header.num_bytes;
   }
   uint8_t* mutable_payload() {
     return reinterpret_cast<uint8_t*>(data_) + data_->header.num_bytes;
   }
+  uint32_t payload_num_bytes() const {
+    assert(data_num_bytes_ >= data_->header.num_bytes);
+    return data_num_bytes_ - data_->header.num_bytes;
+  }
 
   // Access the handles.
   const std::vector<Handle>* handles() const { return &handles_; }
   std::vector<Handle>* mutable_handles() { return &handles_; }
 
  private:
   uint32_t data_num_bytes_;
   internal::MessageData* data_;  // Heap-allocated using malloc.
   std::vector<Handle> handles_;
 
@@ skipping 34 matching lines @@
 // otherwise returns an error code if something went wrong.
 //
 // NOTE: The message hasn't been validated and may be malformed!
 MojoResult ReadAndDispatchMessage(MessagePipeHandle handle,
                                   MessageReceiver* receiver,
                                   bool* receiver_result);
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_