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127 | ------------------------------------------------------------------------------
-- G N A T C O L L --
-- --
-- Copyright (C) 2005-2018, AdaCore --
-- --
-- This library is free software; you can redistribute it and/or modify it --
-- under terms of the GNU General Public License as published by the Free --
-- Software Foundation; either version 3, or (at your option) any later --
-- version. This library is distributed in the hope that it will be useful, --
-- but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- 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/>. --
-- --
------------------------------------------------------------------------------
with System.Storage_Pools; use System, System.Storage_Pools;
with System.Storage_Elements; use System.Storage_Elements;
with Ada.Unchecked_Deallocation;
with Ada.Unchecked_Conversion;
package body GNATCOLL.Storage_Pools.Alignment is
type Storage_Element_Access is access Storage_Element;
function Convert is new Ada.Unchecked_Conversion
(System.Address, Storage_Element_Access);
--------------
-- Allocate --
--------------
overriding procedure Allocate
(Pool : in out Unbounded_No_Reclaim_Align_Pool;
Address : out System.Address;
Storage_Size : Storage_Count;
Alignment : Storage_Count)
is
pragma Unreferenced (Alignment);
-- We need to allocate more memory than actually requested, so that
-- even if "new" returns an incorrect alignment, we have enough spare
-- memory to return the correct alignment. We also always need a buffer
-- of at least two Storage_Element to store the offset between the
-- address from "new" and the one returned by the use, so that
-- Deallocates works appropriately.
-- Worst case is when "new" returned a correctly aligned chunk, and we
-- then need to offset by Pool.Alignment bytes.
Bytes_For_Offset : constant := 3;
Align : constant Storage_Count := Pool.Alignment;
Size : constant Storage_Offset :=
Storage_Size + Align + Bytes_For_Offset - 1;
subtype Local_Storage_Array is Storage_Array (1 .. Size);
type Ptr is access Local_Storage_Array;
Allocated : constant Ptr := new Local_Storage_Array;
Offset : constant Storage_Count :=
Align - Allocated.all'Address mod Align;
begin
Allocated (Offset - 2) := Storage_Element (Offset / 65_536);
Allocated (Offset - 1) := Storage_Element ((Offset mod 65_536) / 256);
Allocated (Offset) := Storage_Element (Offset mod 256);
Address := Allocated.all'Address + Offset;
end Allocate;
----------------
-- Deallocate --
----------------
overriding procedure Deallocate
(Pool : in out Unbounded_No_Reclaim_Align_Pool;
Address : System.Address;
Storage_Size : Storage_Count;
Alignment : Storage_Count)
is
pragma Unreferenced (Alignment);
Size : constant Storage_Offset :=
Storage_Size + Pool.Alignment;
subtype Local_Storage_Array is Storage_Array (1 .. Size);
type Ptr is access Local_Storage_Array;
procedure Unchecked_Free is new Ada.Unchecked_Deallocation
(Local_Storage_Array, Ptr);
function Convert is new Ada.Unchecked_Conversion
(System.Address, Ptr);
Offset_High2 : constant Storage_Element := Convert (Address - 3).all;
Offset_High : constant Storage_Element := Convert (Address - 2).all;
Offset_Low : constant Storage_Element := Convert (Address - 1).all;
Offset : constant Storage_Count :=
Storage_Count (Offset_High2) * 65_536
+ Storage_Count (Offset_High) * 256
+ Storage_Count (Offset_Low);
Real_Address : constant System.Address := Address - Offset;
Var : Ptr := Convert (Real_Address);
begin
Unchecked_Free (Var);
end Deallocate;
------------------
-- Storage_Size --
------------------
overriding function Storage_Size
(Pool : Unbounded_No_Reclaim_Align_Pool) return Storage_Count
is
pragma Unreferenced (Pool);
begin
-- Intuitively, should return System.Memory_Size. But on Sun/Alsys,
-- System.Memory_Size > System.Max_Int, which means all you can do with
-- it is raise CONSTRAINT_ERROR...
return Storage_Count'Last;
end Storage_Size;
end GNATCOLL.Storage_Pools.Alignment;
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