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150 | ------------------------------------------------------------------------------
-- G N A T C O L L --
-- --
-- Copyright (C) 2015-2018, 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.Memory; use System, System.Memory;
with Ada.Unchecked_Conversion;
package body GNATCOLL.Storage_Pools.Headers is
Default_Align : constant Storage_Count :=
Standard'System_Allocator_Alignment;
------------------
-- Header_Pools --
------------------
package body Header_Pools is
type Header is record
Extra : Extra_Header;
end record;
Extra_Bytes : constant Storage_Offset :=
(Header'Max_Size_In_Storage_Elements
- Header'Object_Size / Storage_Unit);
-- If the header is a controlled type, we need to allocate extra size
-- for its Previous and Next pointers. This constant computes how
-- much such extra size is needed.
Header_Size_Bytes : constant Storage_Count :=
Header'Size / Storage_Unit;
Extra_Allocation_Bytes : constant Storage_Count :=
((Header_Size_Bytes + Extra_Bytes + Default_Align - 1)
/ Default_Align) * Default_Align;
-- Allocate a multiple of Default_Align bytes, so that the
-- alignment of the Element_Type is suitable.
function Convert is new Ada.Unchecked_Conversion
(System.Address, Header_Access);
function Address_Header_Of
(Addr : System.Address) return System.Address
is (Addr - Extra_Allocation_Bytes);
-- Compute the address of the header.
-- Do not call with a null pointer.
--------------
-- Allocate --
--------------
overriding procedure Allocate
(Self : in out Header_Pool;
Addr : out System.Address;
Size : System.Storage_Elements.Storage_Count;
Alignment : System.Storage_Elements.Storage_Count)
is
-- The compiler requests a size that include the object size
-- plus any extra header like bounds or next/previous for
-- controlled types. This size also includes a padding to
-- ensure that the element will be properly aligned.
-- The computation is done in s-stposu.adb, in
-- Header_Size_With_Padding.
pragma Unreferenced (Self, Alignment);
Aligned_Size : constant Storage_Count := -- bytes
Size + Extra_Allocation_Bytes;
Allocated : constant System.Address :=
Alloc (size_t (Aligned_Size));
begin
Addr := Allocated + Extra_Allocation_Bytes;
end Allocate;
----------------
-- Deallocate --
----------------
overriding procedure Deallocate
(Self : in out Header_Pool;
Addr : System.Address;
Size : System.Storage_Elements.Storage_Count;
Alignment : System.Storage_Elements.Storage_Count)
is
pragma Unreferenced (Self, Alignment, Size);
Header : constant System.Address := Address_Header_Of (Addr);
begin
System.Memory.Free (Header);
end Deallocate;
-----------
-- Typed --
-----------
package body Typed is
function Header_Of
(Element : Element_Access) return Header_Access
is
Finalization_Size : Integer;
-- If the element_type is a controlled type, this will
-- be the number of extra bytes requested by the compiler in
-- calls to Allocate and Deallocate (see the memory layout
-- description in the specs).
--
-- These extra bytes are automatically added and substracted by
-- the compiler when calling Deallocate, but not when calling
-- Header_Of so we need to take them into account when looking
-- for the our own header.
Descriptor_Size : Integer;
-- Similarily, for bounds information if the element type is
-- an unconstrained array (e.g. String).
begin
if Element = null then
return null;
end if;
Finalization_Size := Element.all'Finalization_Size;
Descriptor_Size := Element_Type'Descriptor_Size / Storage_Unit;
return Convert
(Address_Header_Of
(Element.all'Address
- Storage_Offset (Finalization_Size + Descriptor_Size)));
end Header_Of;
end Typed;
end Header_Pools;
end GNATCOLL.Storage_Pools.Headers;
|