Add multiplexing of message pipes in the new EDK.

mojo/public/c/system/message_pipe.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.
 
 // This file contains types/constants and functions specific to message pipes.
 //
 // Note: This header should be compilable as C.
 
 #ifndef MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_
 #define MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_
 
 #include "mojo/public/c/system/macros.h"
 #include "mojo/public/c/system/system_export.h"
 #include "mojo/public/c/system/types.h"
 
 // |MojoCreateMessagePipeOptions|: Used to specify creation parameters for a
 // message pipe to |MojoCreateMessagePipe()|.
 //   |uint32_t struct_size|: Set to the size of the
 //       |MojoCreateMessagePipeOptions| struct. (Used to allow for future
 //       extensions.)
-//   |MojoCreateMessagePipeOptionsFlags flags|: Reserved for future use.
+//   |MojoCreateMessagePipeOptionsFlags flags|: Used to specify different modes
+//       of operation.
 //       |MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE|: No flags; default mode.
+//       |MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_TRANSFERABLE|: The message pipe
+//           can be sent over another pipe after it's been read or written. This

[yzshen1, 2015/12/03 23:37:51]

Is it "read, written or *waited*"?

[jam, 2015/12/04 05:06:47]

Done.

+//           mode makes message pipes use more resources (one OS pipe each), so
+//           only specify if this functionality is required.
 
 typedef uint32_t MojoCreateMessagePipeOptionsFlags;
 
 #ifdef __cplusplus
 const MojoCreateMessagePipeOptionsFlags
     MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE = 0;
+const MojoCreateMessagePipeOptionsFlags
+    MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_TRANSFERABLE = 1;
 #else
 #define MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE \
   ((MojoCreateMessagePipeOptionsFlags)0)
+#define MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_TRANSFERABLE \
+  ((MojoCreateMessagePipeOptionsFlags)1)
 #endif
 
 MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
 struct MOJO_ALIGNAS(8) MojoCreateMessagePipeOptions {
   uint32_t struct_size;
   MojoCreateMessagePipeOptionsFlags flags;
 };
 MOJO_STATIC_ASSERT(sizeof(MojoCreateMessagePipeOptions) == 8,
                    "MojoCreateMessagePipeOptions has wrong size");
 
@@ skipping 126 matching lines @@
                     uint32_t* num_bytes,    // Optional in/out.
                     MojoHandle* handles,    // Optional out.
                     uint32_t* num_handles,  // Optional in/out.
                     MojoReadMessageFlags flags);
 
 #ifdef __cplusplus
 }  // extern "C"
 #endif
 
 #endif  // MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_