File : adagio-decoupled_file_stream.ads


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--  $Id: adagio-decoupled_file_stream.ads,v 1.3 2004/01/21 21:05:41 Jano Exp $

-- Decoupled file stream

-- Only useful for files, and only for reading (at the moment)

-- The purpose is to use this to read chunks of files, without

-- keeping them opened.

-- Thus, the file can be moved/deleted during reading and an

-- exception will be reported, instead of making the file unusable.

-- This also implies that modifications to the file will go undetected,

-- and that is probably no good.


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

package Adagio.Decoupled_file_stream is

   -- New stream type:

   type Decoupled_file_stream is new 
      Ada.Streams.Root_Stream_Type with private;
   type Object_access is access all Decoupled_file_stream;

   -- Overriden primitives:

   procedure Read(
      Stream : in out Decoupled_file_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 Decoupled_file_stream;
      Item   : in Stream_Element_Array);

   -- Creation. We need a path to file:

   procedure Get_decoupled_file_stream
     (Stream: out Decoupled_file_stream; 
      File:   String); 

   -- Seek

   procedure Set_position
     (Stream: in out Decoupled_file_stream;
      Pos: Stream_IO.Positive_count);

   -- Size

   function Size(Stream: Decoupled_file_stream) return Stream_IO.Count;

   -- EOF

   function End_of_stream(Stream: Decoupled_file_stream) return boolean;

private

   type Decoupled_file_stream is new Ada.Streams.Root_Stream_Type 
   with record
      File: UString:= To_UString("");
      Filepos: Stream_IO.Positive_count:= 1;
   end record;

end Adagio.Decoupled_file_stream;