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Date: Fri, 14 Dec 2018 09:50:08 -0800 (PST)
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Subject: gnatcol json vs network read
From: Stephen Leake <stephen_leake@stephe-leake.org>
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Xref: reader01.eternal-september.org comp.lang.ada:55038
Date: 2018-12-14T09:50:08-08:00
List-Id: <comp.lang.ada>

I'm reading json over a network, with code like:

   function Check_Ack (DB : not null access Database) return   
      GNATCOLL.JSON.JSON_Value
   is
      use GNATCOLL.JSON;
      Msg : constant String := String (Network_String'Input (DB.Stream));
   begin
      if DB.Verbosity > 1  then
         Ada.Text_IO.Put_Line ("Remote: " & Msg);
      end if;

      declare
         Response : constant JSON_Value := Read (Msg);
      begin
         if Response.Get ("Status") /= Ack_Nack'Image (Ack) then
            raise SAL.Invalid_Operation with Response.Get ("Message");
         end if;
         return Response.Get ("Data");
      end;
   end Check_Ack;

Occasionally, this will throw INVALID_JSON_STREAM <data>:1:155: empty stream

Apparently this is because the network is sending a data packet with less then a whole JSON object; in the case I'm currently debugging, it's missing two closing }.

So I need to check Msg for complete syntax before calling Read. However, GNATCOLL.JSON does not provide a function for that, and event the lower level Read in gnatcol-json.adb raises the exception.

So I guess I'll write a {} counter, and wait for more data from the network if the first object is not complete.

Has anyone else dealt with this problem?

-- Stephe