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natools-cron.ads
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------------------------------------------------------------------------------
-- Copyright (c) 2014-2017, Natacha Porté --
-- --
-- Permission to use, copy, modify, and distribute this software for any --
-- purpose with or without fee is hereby granted, provided that the above --
-- copyright notice and this permission notice appear in all copies. --
-- --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. --
------------------------------------------------------------------------------
------------------------------------------------------------------------------
-- Natools.Cron is a low-overhead, low-precision implementation of periodic --
-- callbacks, similar to UNIX cron daemon. --
-- Note that callbacks are executed sequentially in a single thread, and --
-- ticks may be skipped when computing resources lack. --
-- If you need more precision and/or more reliability, you might want to --
-- consider using Ada.Real_Time.Timing_Events instead. --
------------------------------------------------------------------------------
with Ada.Calendar;
private with Ada.Containers.Doubly_Linked_Lists;
private with Ada.Containers.Ordered_Maps;
private with Ada.Finalization;
private with Ada.Unchecked_Deallocation;
private with Natools.References;
private with Natools.Storage_Pools;
package Natools.Cron is
type Callback is interface;
procedure Run (Object : in out Callback) is abstract;
type Periodic_Time is record
Origin : Ada.Calendar.Time;
Period : Duration;
end record;
type Cron_Entry is tagged limited private;
pragma Preelaborable_Initialization (Cron_Entry);
function Create
(Time : in Periodic_Time;
Callback : in Cron.Callback'Class)
return Cron_Entry;
-- Create a new entry with the given parameters
function Create
(Origin : in Ada.Calendar.Time;
Callback : in Cron.Callback'Class)
return Cron_Entry;
-- Create a new entry that executes only once, at the given time
function Create
(Period : in Duration;
Callback : in Cron.Callback'Class)
return Cron_Entry;
-- Create a new entry starting within a period from now
procedure Set
(Self : in out Cron_Entry;
Time : in Periodic_Time;
Callback : in Cron.Callback'Class);
-- Reset an entry with the given parameters
procedure Set
(Self : in out Cron_Entry;
Origin : in Ada.Calendar.Time;
Callback : in Cron.Callback'Class);
-- Reset entry with the given parameters, running only once
procedure Set
(Self : in out Cron_Entry;
Period : in Duration;
Callback : in Cron.Callback'Class);
-- Reset entry with the given parameters, starting one period from now
procedure Reset (Self : in out Cron_Entry);
-- Clear internal state and remove associated entry from database.
-- Note that if the callback procedure is currently running, it will
-- continue until it returns, so the callback object may outlive
-- the call to Reset, plan concurrency accordingly.
private
package Callback_Refs is new References
(Callback'Class,
Storage_Pools.Access_In_Default_Pool'Storage_Pool,
Storage_Pools.Access_In_Default_Pool'Storage_Pool);
type Cron_Entry is new Ada.Finalization.Limited_Controlled with record
Callback : Callback_Refs.Reference;
end record;
overriding procedure Finalize (Object : in out Cron_Entry);
package Event_Lists is new Ada.Containers.Doubly_Linked_Lists
(Callback_Refs.Reference, Callback_Refs."=");
type Event_List is new Callback with record
List : Event_Lists.List;
end record;
overriding procedure Run (Self : in out Event_List);
-- Sequentially run the contained events
procedure Append
(Self : in out Event_List;
Ref : in Callback_Refs.Reference);
-- Append Ref at the end of Self.List
procedure Prepend
(Self : in out Event_List;
Ref : in Callback_Refs.Reference);
-- Prepend Ref at the beginning of Self.List
procedure Remove
(Self : in out Event_List;
Ref : in Callback_Refs.Reference;
Removed : out Boolean);
-- Remove Ref from Self.List, through a linear search
function Is_Empty (Self : Event_List) return Boolean;
-- Return whether Self contains any element
function "<" (Left, Right : Periodic_Time) return Boolean;
-- Comparison function for ordered map
package Entry_Maps is new Ada.Containers.Ordered_Maps
(Periodic_Time, Callback_Refs.Reference, "<", Callback_Refs."=");
protected Database is
procedure Insert
(Time : in Periodic_Time;
Callback : in Callback_Refs.Reference);
-- Insert Callback into the database, adjusting Time.Origin
-- to be in the future.
procedure Remove (Callback : in Callback_Refs.Reference);
-- Remove Callback from the database
procedure Update (Callback : in Callback_Refs.Reference);
-- Update Time.Origin associated with Callback so that
-- it is in the future.
procedure Get_First
(Time : out Periodic_Time;
Callback : out Callback_Refs.Reference);
-- Return the next active callback, or an empty reference when
-- the database is empty (to signal task termination).
procedure Get_Event_List
(Source : in Event_List;
List : out Event_Lists.List);
-- Initialize an event list from Source without
-- any concurrent tampering of the list.
entry Update_Notification;
-- Block as long as the next active item does not change
private
Map : Entry_Maps.Map;
First_Changed : Boolean := False;
end Database;
task type Worker is
end Worker;
type Worker_Access is access Worker;
procedure Unchecked_Free is new Ada.Unchecked_Deallocation
(Worker, Worker_Access);
Global_Worker : Worker_Access := null;
end Natools.Cron;