File : adagio-throttle_stream.ads


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--  $Id: adagio-throttle_stream.ads,v 1.3 2004/01/21 21:05:42 Jano Exp $


-- Throttle stream


with Ada.Streams;                use Ada.Streams;
use Ada;

with Adagio.Throttler;

package Adagio.Throttle_stream is

   -- New stream type:

   type Throttle_stream (Throttle: access Throttler.Object) is new 
      Ada.Streams.Root_Stream_Type with private;

   type Stream_access is access all Throttle_stream;

   -- Overriden primitives:

   -- At each read, a Throttle.Cycle_work is performed.

   -- Thus, a Start_work should be ensured right before use.

   -- Lacking that, a HUGE delay could be triggered.

   -- Note that the creator will do that.

   procedure Read(
      Stream : in out Throttle_stream;
      Item   : out Stream_Element_Array;
      Last   : out Stream_Element_Offset);

   -- Only reading is implemented. 

   -- Thus, any call to this raises Unimplemented_error.

        procedure Write(
      Stream : in out Throttle_stream;
      Item   : in Stream_Element_Array);

   -- Creation. It links a new buffered stream with any other stream:

   -- Will perform a Throttle.Start_work;

   procedure Get_throttle_stream
     (TStream: in out Throttle_stream; 
      Stream : access Streams.Root_stream_type'Class);

private

   type Counter_type is mod 2 ** 14;

   type Root_stream_access is access all Streams.Root_stream_type'Class;

   type Throttle_stream(Throttle: access Throttler.Object) is new 
      Ada.Streams.Root_Stream_Type with 
   record
      Source: Root_stream_access;  -- or any descendent.

      Counter: Counter_type:= 0;
   end record;

end Adagio.Throttle_stream;