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8.1.5.3 Transmitting Dynamic Structure

with Ada.Streams; use Ada.Streams;
package StringArrayStream is
   pragma Remote_Types;

   type List is private;
   procedure Append (L : access List; O : in String);
   function  Delete (L : access List) return String;

private
   --  implementation removed
end StringArrayStream;

Non-remote access types cannot be declared in the public part of a remote types unit. However, it is possible to define private non-remote access types as long as the user provides its marshalling procedures, that is to say the mechanism needed to place a value of the type into a communication stream. The code below describes how to transmit a linked structure.

The package declaration provides a type definition of single-linked lists of unbounded strings. An implementation of the marshalling operations could be the following: 

package body StringArrayStream is
   procedure Read
     (S : access Root_Stream_Type'Class;
      L : out List) is
   begin
      if Boolean'Input (S) then
         L := new Node;
         L.Content := new String'(String'Input (S));
         List'Read (S, L.Next);
      else
         L := null;
      end if;
   end Read;

   procedure Write
     (S : access Root_Stream_Type'Class;
      L : in List) is
   begin
      if L = null then
         Boolean'Output (S, False);
      else
         Boolean'Output (S, True);
         String'Output (S, L.Content.all);
         List'Write (S, L.Next);
      end if;
   end Write;

   --  [...] Other services
end StringArrayStream;