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

mojo/edk/system/channel.h

Index: mojo/edk/system/channel.h
diff --git a/mojo/edk/system/channel.h b/mojo/edk/system/channel.h
index 0d7ccdb613f591a8659dad663f3741a628e0a549..e6ca4b961d5ee6d86f934eab88946d8819da1012 100644
--- a/mojo/edk/system/channel.h
+++ b/mojo/edk/system/channel.h
@@ -66,6 +66,17 @@ class Channel : public base::RefCountedThreadSafe<Channel> {
       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
@@ -111,6 +122,11 @@ class Channel : public base::RefCountedThreadSafe<Channel> {
     // 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.
@@ -138,6 +154,12 @@ class Channel : public base::RefCountedThreadSafe<Channel> {
     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nit: this comment appears to be out of date since they're in the extra header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);
   };