Mojo: Allow dispatchers to attach PlatformHandles to the MessageInTransit on serialization.

mojo/system/message_in_transit.h

 // Copyright 2013 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_SYSTEM_MESSAGE_IN_TRANSIT_H_
 #define MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 52 matching lines @@
   static const EndpointId kInvalidEndpointId = 0;
 
   // Messages (the header and data) must always be aligned to a multiple of this
   // quantity (which must be a power of 2).
   static const size_t kMessageAlignment = 8;
 
   // The maximum size of a single serialized dispatcher. This must be a multiple
   // of |kMessageAlignment|.
   static const size_t kMaxSerializedDispatcherSize = 10000;
 
+  // The maximum number of platform handles to attach for a single serialized
+  // dispatcher.
+  static const size_t kMaxSerializedDispatcherPlatformHandles = 2;
+
   // Forward-declare |Header| so that |View| can use it:
  private:
   struct Header;
  public:
   // This represents a view of serialized message data in a raw buffer.
   class MOJO_SYSTEM_IMPL_EXPORT View {
    public:
     // Constructs a view from the given buffer of the given size. (The size must
     // be as provided by |MessageInTransit::GetNextMessageSize()|.) The buffer
     // must remain alive/unmodified through the lifetime of this object.
@@ skipping 175 matching lines @@
   struct HandleTableEntry {
     int32_t type;  // From |Dispatcher::Type| (|kTypeUnknown| for "invalid").
     uint32_t offset;  // Relative to the start of the secondary buffer.
     uint32_t size;  // (Not including any padding.)
     uint32_t unused;
   };
 
   // The maximum possible size of a valid secondary buffer.
   static const size_t kMaxSecondaryBufferSize;
 
+  // The maximum total number of platform handles that may be attached.
+  static const size_t kMaxPlatformHandles;
+
   // Validates the secondary buffer. Returns null on success, or a
   // human-readable error message (meant for logging/debugging) on error.
   static const char* ValidateSecondaryBuffer(size_t num_handles,
                                              const void* secondary_buffer,
                                              size_t secondary_buffer_size);
 
   const Header* header() const {
     return static_cast<const Header*>(main_buffer_);
   }
   Header* header() { return static_cast<Header*>(main_buffer_); }
@@ skipping 18 matching lines @@
   // TODO(vtl): With C++11, change it to a vector of |ScopedPlatformHandles|.
   scoped_ptr<std::vector<embedder::PlatformHandle> > platform_handles_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageInTransit);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_