-- --
-- S p e c --
-- --
--- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
--- ware Foundation; either version 2, or (at your option) any later ver- --
+-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
--- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNAT; see file COPYING. If not, write --
--- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
--- Boston, MA 02110-1301, USA. --
+-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
--- As a special exception, if other files instantiate generics from this --
--- unit, or you link this unit with other files to produce an executable, --
--- this unit does not by itself cause the resulting executable to be --
--- covered by the GNU General Public License. This exception does not --
--- however invalidate any other reasons why the executable file might be --
--- covered by the GNU Public License. --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception, --
+-- version 3.1, as published by the Free Software Foundation. --
+-- --
+-- You should have received a copy of the GNU General Public License and --
+-- a copy of the GCC Runtime Library Exception along with this program; --
+-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
+-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- - all ia64 platforms
-- - all PowerPC platforms
-- - all SPARC V9 platforms
+-- - all x86 platforms
-- - all x86_64 platforms
with Ada.Strings.Wide_Maps;
private with Ada.Finalization;
-private with Interfaces;
+private with System.Atomic_Counters;
package Ada.Strings.Wide_Unbounded is
pragma Preelaborate;
package AF renames Ada.Finalization;
type Shared_Wide_String (Max_Length : Natural) is limited record
- Counter : aliased Interfaces.Unsigned_32 := 1;
- -- Reference counter.
+ Counter : System.Atomic_Counters.Atomic_Counter;
+ -- Reference counter
- Last : Natural := 0;
- Data : Wide_String (1 .. Max_Length);
+ Last : Natural := 0;
+ Data : Wide_String (1 .. Max_Length);
-- Last is the index of last significant element of the Data. All
-- elements with larger indices are just an extra room.
end record;
-- Increment reference counter.
procedure Unreference (Item : not null Shared_Wide_String_Access);
- -- Decrement reference counter. Deallocate Item when reference counter is
- -- zero.
+ -- Decrement reference counter. Deallocate Item when ref counter is zero
function Can_Be_Reused
(Item : Shared_Wide_String_Access;
function To_Unbounded (S : Wide_String) return Unbounded_Wide_String
renames To_Unbounded_Wide_String;
- -- This renames are here only to be used in the pragma Stream_Convert.
+ -- This renames are here only to be used in the pragma Stream_Convert
type Unbounded_Wide_String is new AF.Controlled with record
Reference : Shared_Wide_String_Access := Empty_Shared_Wide_String'Access;
-- The Unbounded_Wide_String uses several techniques to increase speed of
-- the application:
+
-- - implicit sharing or copy-on-write. Unbounded_Wide_String contains
-- only the reference to the data which is shared between several
-- instances. The shared data is reallocated only when its value is
-- changed and the object mutation can't be used or it is inefficient to
-- use it;
+
-- - object mutation. Shared data object can be reused without memory
-- reallocation when all of the following requirements are meat:
-- - shared data object don't used anywhere longer;
-- - its size is sufficient to store new value;
-- - the gap after reuse is less then some threshold.
+
-- - memory preallocation. Most of used memory allocation algorithms
-- aligns allocated segment on the some boundary, thus some amount of
-- additional memory can be preallocated without any impact. Such
-- preallocated memory can used later by Append/Insert operations
-- without reallocation.
- --
+
-- Reference counting uses GCC builtin atomic operations, which allows to
-- safely share internal data between Ada tasks. Nevertheless, this not
-- make objects of Unbounded_Wide_String thread-safe, so each instance
overriding procedure Finalize (Object : in out Unbounded_Wide_String);
Null_Unbounded_Wide_String : constant Unbounded_Wide_String :=
- (AF.Controlled with
- Reference => Empty_Shared_Wide_String'Access);
+ (AF.Controlled with
+ Reference =>
+ Empty_Shared_Wide_String'Access);
end Ada.Strings.Wide_Unbounded;
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