From: Warren <ve3wwg@gmail.com>
Subject: Generic Embedded List Nodes
Date: Sat, 18 Jun 2016 15:52:00 -0700 (PDT)
Date: 2016-06-18T15:52:00-07:00 [thread overview]
Message-ID: <66c14298-c62d-4f4b-b0c0-e969454f9334@googlegroups.com> (raw)
Getting back to Ada after a hiatus, I currently have a need to build a
generic package to implement "embedded list node" lists. The advantage
is high performance in a server setting to avoid underlying malloc/free
calls.
The idea is that the list node resides within the structure/tagged type,
and acts as a doubly linked list node when in a list. The Emb_Node can
be used as a list head when itself (or as part of another structure). This
kind of thing is done in the Linux kernel, for example.
The Emb_Node and its operations are trivial. The problem occurs when
you traverse a linked list of Emb_Nodes (or its derived type). With
a given node, I need to then access the object that _contains_ it. In
C/C++ you do some offset calculation from the node address back to
the owning struct/class.
My idea (in Ada) was to save some kind of access value in a type
derived from Emb_List. But that is where the trouble starts.
package Emb_List is
type Emb_Node is tagged private;
procedure Insert_Head(Head: access Emb_Node; Node: access Emb_Node);
procedure Unlink(Node: access Emb_Node);
private
type Emb_Node is tagged
record
Next: access Emb_Node; -- Ptr to next node in list (if any)
Prev: access Emb_Node; -- Ptr to prev node in list (if any)
end record;
end Emb_List;
The generic extension (below) was intended to hold the reference to the
containing object, which is where the trouble starts. I was hoping this
would work, but running into "missing full declaration for private
extension".
generic
type Object_Type is tagged private;
package Emb_List.Nodes is
type Node_Type(Obj: access Object_Type) is new Emb_Node;
function Object(Node: Node_Type) return Object_Type;
end Emb_List.Nodes;
The other end of the challenge will be to have the Node_Type save the
owning object access value at the time it is created:
type Something_New_Type is tagged
record
Stuff: Natural;
Timeout_Node: Node_Type(some access to this record);
...
end record;
I am trying to avoid using 'Address for this, since there is likely a
way to do this "right".
Warren.
next reply other threads:[~2016-06-18 22:52 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-18 22:52 Warren [this message]
2016-06-18 23:40 ` Generic Embedded List Nodes Jeffrey R. Carter
2016-06-19 2:15 ` Warren
2016-06-19 3:04 ` Jeffrey R. Carter
2016-06-19 2:14 ` Jeremiah
2016-06-19 2:21 ` Warren
2016-06-19 2:50 ` Warren
2016-06-19 4:45 ` Simon Wright
2016-06-19 18:27 ` Warren
2016-06-19 19:04 ` Dmitry A. Kazakov
2016-06-19 20:13 ` Warren
2016-06-19 20:35 ` Dmitry A. Kazakov
2016-06-20 2:42 ` Warren
2016-06-20 7:25 ` Dmitry A. Kazakov
2016-06-20 12:26 ` Warren
2016-06-20 19:33 ` Niklas Holsti
2016-06-21 2:20 ` Warren
2016-06-21 5:52 ` Niklas Holsti
2016-06-21 7:15 ` Dmitry A. Kazakov
2016-06-21 18:54 ` Niklas Holsti
2016-06-21 19:54 ` Dmitry A. Kazakov
2016-06-21 10:31 ` Warren
2016-06-21 17:13 ` Jeffrey R. Carter
2016-06-21 18:56 ` Niklas Holsti
2016-06-21 20:13 ` Warren
2016-06-21 21:38 ` Niklas Holsti
2016-06-23 2:12 ` Warren
2016-06-23 8:19 ` Niklas Holsti
2016-06-23 12:37 ` Warren
2016-06-23 15:36 ` Niklas Holsti
2016-06-24 1:55 ` Warren
2016-06-24 12:49 ` Warren
2016-06-25 5:50 ` Niklas Holsti
2016-06-26 1:36 ` Warren
2016-07-01 13:49 ` Warren
2016-07-01 16:28 ` Warren
2016-06-24 20:25 ` Warren
2016-06-22 13:01 ` G.B.
2016-06-23 2:30 ` Warren
2016-06-20 6:08 ` Niklas Holsti
2016-06-20 12:20 ` Warren
2016-06-20 19:47 ` Shark8
2016-06-21 2:28 ` Warren
2016-06-21 7:21 ` Dmitry A. Kazakov
2016-06-21 10:32 ` Warren
2016-06-21 11:56 ` Dmitry A. Kazakov
2016-06-21 13:39 ` Warren
2016-06-21 14:04 ` Dmitry A. Kazakov
2016-06-23 0:37 ` Randy Brukardt
2016-06-23 2:25 ` Warren
2016-07-01 19:50 ` brbarkstrom
2016-07-02 1:55 ` Warren
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox