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--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                         S Y S T E M . M E M O R Y                        --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 2001-2003 Free Software Foundation, Inc.          --

--                                                                          --

-- 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- --

-- 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.                                              --

--                                                                          --

-- 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.                                      --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

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--  This package provides the low level memory allocation/deallocation

--  mechanisms used by GNAT.

--  To provide an alternate implementation, simply recompile the modified

--  body of this package with gnatmake -u -a -g s-memory.adb and make sure

--  that the ali and object files for this unit are found in the object

--  search path.

--  This unit may be used directly from an application program by providing

--  an appropriate WITH, and the interface can be expected to remain stable.

package System.Memory is

   pragma Elaborate_Body;

   type size_t is mod 2 ** Standard'Address_Size;

   --  Note: the reason we redefine this here instead of using the

   --  definition in Interfaces.C is that we do not want to drag in

   --  all of Interfaces.C just because System.Memory is used.

   function Alloc (Size : size_t) return System.Address;

   --  This is the low level allocation routine. Given a size in storage

   --  units, it returns the address of a maximally aligned block of

   --  memory. The implementation of this routine is guaranteed to be

   --  task safe, and also aborts are deferred if necessary.

   --

   --  If size_t is set to size_t'Last on entry, then a Storage_Error

   --  exception is raised with a message "object too large".

   --

   --  If size_t is set to zero on entry, then a minimal (but non-zero)

   --  size block is allocated.

   --

   --  Note: this is roughly equivalent to the standard C malloc call

   --  with the additional semantics as described above.

   procedure Free (Ptr : System.Address);

   --  This is the low level free routine. It frees a block previously

   --  allocated with a call to Alloc. As in the case of Alloc, this

   --  call is guaranteed task safe, and aborts are deferred.

   --

   --  Note: this is roughly equivalent to the standard C free call

   --  with the additional semantics as described above.

   function Realloc

     (Ptr  : System.Address;

      Size : size_t)

      return System.Address;

   --  This is the low level reallocation routine. It takes an existing

   --  block address returned by a previous call to Alloc or Realloc,

   --  and reallocates the block. The size can either be increased or

   --  decreased. If possible the reallocation is done in place, so that

   --  the returned result is the same as the value of Ptr on entry.

   --  However, it may be necessary to relocate the block to another

   --  address, in which case the information is copied to the new

   --  block, and the old block is freed. The implementation of this

   --  routine is guaranteed to be task safe, and also aborts are

   --  deferred as necessary.

   --

   --  If size_t is set to size_t'Last on entry, then a Storage_Error

   --  exception is raised with a message "object too large".

   --

   --  If size_t is set to zero on entry, then a minimal (but non-zero)

   --  size block is allocated.

   --

   --  Note: this is roughly equivalent to the standard C realloc call

   --  with the additional semantics as described above.

private

   --  The following names are used from the generated compiler code

   pragma Export (C, Alloc,   "__gnat_malloc");

   pragma Export (C, Free,    "__gnat_free");

   pragma Export (C, Realloc, "__gnat_realloc");

end System.Memory;