[mojo-edk] Add support for transferring mach ports.

mojo/edk/system/channel.h

 // Copyright 2016 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_EDK_SYSTEM_CHANNEL_H_
 #define MOJO_EDK_SYSTEM_CHANNEL_H_
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 48 matching lines @@
       // Number of attached handles. May be less than the reserved handle
       // storage size in this message on platforms that serialise handles as
       // data (i.e. HANDLEs on Windows, Mach ports on OSX).
       uint16_t num_handles;
 
       MessageType message_type;
 
       char padding[6];
 #endif  // defined(OS_CHROMEOS)
     };
+
+#if defined(OS_MACOSX)
+    struct MachPortsEntry {
+      uint16_t index;
+      uint32_t mach_port;
+      static_assert(sizeof(mach_port_t) <= sizeof(uint32_t),
+                    "mach_port_t must be smaller than uint32_t");

[Ken Rockot(use gerrit already), 2016/03/09 08:34:31]

nit: must be no larger than uint32_t

[Anand Mistry (off Chromium), 2016/03/11 07:44:18]

Done.

+    };
+    static_assert(sizeof(MachPortsEntry) == 6,
+                  "sizeof(MachPortsEntry) must be 6 bytes");
+#endif
 #pragma pack(pop)
 
     // Allocates and owns a buffer for message data with enough capacity for
     // |payload_size| bytes plus a header, plus |max_handles| platform handles.
     Message(size_t payload_size,
             size_t max_handles,
             Header::MessageType message_type = Header::MessageType::NORMAL);
 
     ~Message();
 
@@ skipping 25 matching lines @@
     bool has_handles() const { return header_->num_handles > 0; }
     PlatformHandle* handles();
 #if defined(OS_MACOSX) && !defined(OS_IOS)
     bool has_mach_ports() const;
 #endif
 
     // Note: SetHandles() and TakeHandles() invalidate any previous value of
     // handles().
     void SetHandles(ScopedPlatformHandleVectorPtr new_handles);
     ScopedPlatformHandleVectorPtr TakeHandles();
+    // Version of TakeHandles that returns a vector of platform handles suitable
+    // for transfer over an underlying OS mechanism. i.e. file descriptors over
+    // a unix domain socket. Any handle that cannot be transferred this way,
+    // such as Mach port, will be removed.
+    ScopedPlatformHandleVectorPtr TakeHandlesForTransport();
 
 #if defined(OS_WIN)
     // Prepares the handles in this message for use in a different process.
     // Upon calling this the handles should belong to |from_process|; after the
     // call they'll belong to |to_process|. The source handles are always
     // closed by this call. Returns false iff one or more handles failed
     // duplication.
     static bool RewriteHandles(base::ProcessHandle from_process,
                                base::ProcessHandle to_process,
                                PlatformHandle* handles,
                                size_t num_handles);
 #endif
 
    private:
     size_t size_;
     size_t max_handles_;
     char* data_;
     Header* header_;
 
 #if defined(OS_WIN)
     // On Windows, handles are serialized in the data buffer along with the
     // rest of the payload.
     PlatformHandle* handles_ = nullptr;
 #else
     ScopedPlatformHandleVectorPtr handle_vector_;
 #endif
 
+#if defined(OS_MACOSX)
+    // On OSX, handles which are mach ports are serialised into the data buffer
+    // after the rest of the payload.
+    MachPortsEntry* mach_ports_ = nullptr;

[Ken Rockot(use gerrit already), 2016/03/09 08:34:31]

nit: this comment appears to be out of date since they're in the extra header
now

[Anand Mistry (off Chromium), 2016/03/11 07:44:17]

Done, and updated the windows comment.

+#endif
+
     DISALLOW_COPY_AND_ASSIGN(Message);
   };
 
   // Delegate methods are called from the I/O task runner with which the Channel
   // was created (see Channel::Create).
   class Delegate {
    public:
     virtual ~Delegate() {}
 
     // Notify of a received message. |payload| is not owned and must not be
@@ skipping 81 matching lines @@
   Delegate* delegate_;
   const scoped_ptr<ReadBuffer> read_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(Channel);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_CHANNEL_H_