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165 | -----------------------------------------------------------------------
-- ADO Sequences -- Database sequence generator
-- Copyright (C) 2009, 2010, 2011, 2012, 2017, 2018 Stephane Carrez
-- Written by Stephane Carrez (Stephane.Carrez@gmail.com)
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
-----------------------------------------------------------------------
with Ada.Finalization;
with Ada.Strings.Unbounded.Hash;
with Ada.Containers.Hashed_Maps;
with ADO.Sessions;
with ADO.Objects;
limited with ADO.Sessions.Factory;
-- == Sequence Generators ==
-- The sequence generator is responsible for creating unique ID's
-- across all database objects.
--
-- Each table can be associated with a sequence generator.
-- The sequence factory is shared by several sessions and the
-- implementation is thread-safe.
--
-- The `HiLoGenerator` implements a simple High Low sequence generator
-- by using sequences that avoid to access the database.
--
-- Example:
--
-- F : Factory;
-- Id : Identifier;
-- ...
-- Allocate (Manager => F, Name => "user", Id => Id);
--
-- @include ado-sequences-hilo.ads
package ADO.Sequences is
-- Exception raised when the sequence generator fails to allocate an id.
Allocate_Error : exception;
type Session_Factory_Access is access all ADO.Sessions.Factory.Session_Factory'Class;
-- ------------------------------
-- Abstract sequence generator
-- ------------------------------
type Generator is abstract new Ada.Finalization.Limited_Controlled with private;
type Generator_Access is access all Generator'Class;
-- Get the name of the sequence.
function Get_Sequence_Name (Gen : in Generator'Class) return String;
-- Allocate an identifier using the generator.
procedure Allocate (Gen : in out Generator;
Id : in out Objects.Object_Record'Class) is abstract;
-- Get a session to connect to the database.
function Get_Session (Gen : in Generator) return ADO.Sessions.Master_Session'Class;
type Generator_Factory is access
function (Sess_Factory : in Session_Factory_Access)
return Generator_Access;
-- ------------------------------
-- Sequence factory
-- ------------------------------
-- The sequence <b>Factory</b> allocates unique ids for new objects.
-- The factory is shared by all connections to the same database.
type Factory is limited private;
type Factory_Access is access all Factory;
-- Allocate a unique identifier for the given sequence.
procedure Allocate (Manager : in out Factory;
Id : in out Objects.Object_Record'Class);
-- Set a generator to be used for the given sequence.
procedure Set_Generator (Manager : in out Factory;
Name : in String;
Gen : in Generator_Access);
-- Set the default factory for creating generators.
-- The default factory is the HiLo generator.
procedure Set_Default_Generator
(Manager : in out Factory;
Factory : in Generator_Factory;
Sess_Factory : in Session_Factory_Access);
private
use Ada.Strings.Unbounded;
type Generator is abstract new Ada.Finalization.Limited_Controlled with record
Name : Unbounded_String;
Factory : Session_Factory_Access;
end record;
-- Each sequence generator is accessed through a protected type
-- to make sure the allocation is unique and works in multi-threaded
-- environments.
protected type Sequence_Generator is
-- Allocate a unique identifier for the given sequence.
procedure Allocate (Id : in out Objects.Object_Record'Class);
procedure Set_Generator (Name : in Unbounded_String;
Gen : in Generator_Access);
-- Free the generator
procedure Clear;
private
Generator : Generator_Access;
end Sequence_Generator;
type Sequence_Generator_Access is access all Sequence_Generator;
-- Map to keep track of allocation generators for each sequence.
package Sequence_Maps is new Ada.Containers.Hashed_Maps
(Key_Type => Unbounded_String,
Element_Type => Sequence_Generator_Access,
Hash => Ada.Strings.Unbounded.Hash,
Equivalent_Keys => "=",
"=" => "=");
-- The sequence factory map is also accessed through a protected type.
protected type Factory_Map is
-- Get the sequence generator associated with the name.
-- If there is no such generator, an entry is created by using
-- the default generator.
procedure Get_Generator (Name : in Unbounded_String;
Gen : out Sequence_Generator_Access);
-- Set the sequence generator associated with the name.
procedure Set_Generator (Name : in Unbounded_String;
Gen : in Sequence_Generator_Access);
-- Set the default sequence generator.
procedure Set_Default_Generator
(Gen : in Generator_Factory;
Factory : in Session_Factory_Access);
-- Clear the factory map.
procedure Clear;
private
Map : Sequence_Maps.Map;
Create_Generator : Generator_Factory;
Sess_Factory : Session_Factory_Access;
end Factory_Map;
type Factory is new Ada.Finalization.Limited_Controlled with record
Map : Factory_Map;
end record;
overriding
procedure Finalize (Manager : in out Factory);
end ADO.Sequences;
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