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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Custom Storage Pool questions
Date: Sun, 3 Oct 2021 10:52:35 +0200
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On 2021-10-03 01:19, Jere wrote:
> I was thinking more along the lines of adding a classwide operation on the
> root storage pool type.

You don't need that. As I proposed in another response, one add a new 
primitive operations:

    procedure Allocate_Segment
              (  Pool            : in out Root_Storage_Pool;
                 Storage_Address : out Address;
                 Size            : Storage_Count;
                 Alignment       : Storage_Count;
                 Sequence_No     : Positive
              );

Note, it is not abstract. The implementation dispatches to Allocate:

    procedure Allocate_Segment
              (  Pool            : in out Root_Storage_Pool;
                 Storage_Address : out Address;
                 Size            : Storage_Count;
                 Alignment       : Storage_Count;
                 Head            : Address; -- The first block address
                 Sequence_No     : Positive
              )  is
    begin
       Root_Storage_Pool'Class (Pool).Allocate
       (  Storage_Address,
          Size,
          Alignment
       );
    end Allocate_Segment;

Similarly goes Deallocate_Segment.

The object allocation protocol:

    Take mutex
    Allocate (...);            -- The head, passed down in further calls
    Allocate_Segment (..., 1); -- First auxiliary block
    ...
    Allocate_Segment (..., N); -- Last auxiliary block
    Release mutex

Deallocation protocol:

    Take mutex
    Dellocate_Segment (..., 1); -- Last auxiliary block
    ...
    Dellocate_Segment (..., N); -- First auxiliary block
    Deallocate (...);           -- The head
    Release mutex

That is 100% backward compatible.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de