Modify areas that still assumed Pipe::message_id was exactly a u32bit.

This was done by replacing Pipe::message_id with a completely opaque
type and adding only the necessary operations. In this revision
Pipe::message_id does remain a u32bit. However it may become an
opaque type in the future.

Move the Invalid_Message_Number exception to Pipe since that is the only
piece of code which throws it.

1 files changed, 7 insertions, 1 deletions

diff --git a/include/pipe.h b/include/pipe.h
index 20fdc6a41..89f1ac4db 100644
--- a/include/pipe.h
+++ b/include/pipe.h
@@ -20,6 +20,12 @@ class Pipe : public DataSource
    public:
       typedef u32bit message_id;
 
+      class Invalid_Message_Number : public Invalid_Argument
+         {
+         public:
+            Invalid_Message_Number(const std::string&, message_id);
+         };
+
       static const message_id LAST_MESSAGE, DEFAULT_MESSAGE;
 
       void write(const byte[], u32bit);
@@ -48,7 +54,7 @@ class Pipe : public DataSource
 
       message_id default_msg() const { return default_read; }
       void set_default_msg(message_id);
-      u32bit message_count() const;
+      message_id message_count() const;
       bool end_of_data() const;
 
       void start_msg();