1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--                         S Y S T E M . M E M O R Y                        --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 2001-2003 Free Software Foundation, Inc.          --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
19-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
20-- MA 02111-1307, USA.                                                      --
21--                                                                          --
22-- As a special exception,  if other files  instantiate  generics from this --
23-- unit, or you link  this unit with other files  to produce an executable, --
24-- this  unit  does not  by itself cause  the resulting  executable  to  be --
25-- covered  by the  GNU  General  Public  License.  This exception does not --
26-- however invalidate  any other reasons why  the executable file  might be --
27-- covered by the  GNU Public License.                                      --
28--                                                                          --
29-- GNAT was originally developed  by the GNAT team at  New York University. --
30-- Extensive contributions were provided by Ada Core Technologies Inc.      --
31--                                                                          --
32------------------------------------------------------------------------------
33
34--  This package provides the low level memory allocation/deallocation
35--  mechanisms used by GNAT.
36
37--  To provide an alternate implementation, simply recompile the modified
38--  body of this package with gnatmake -u -a -g s-memory.adb and make sure
39--  that the ali and object files for this unit are found in the object
40--  search path.
41
42--  This unit may be used directly from an application program by providing
43--  an appropriate WITH, and the interface can be expected to remain stable.
44
45package System.Memory is
46   pragma Elaborate_Body;
47
48   type size_t is mod 2 ** Standard'Address_Size;
49   --  Note: the reason we redefine this here instead of using the
50   --  definition in Interfaces.C is that we do not want to drag in
51   --  all of Interfaces.C just because System.Memory is used.
52
53   function Alloc (Size : size_t) return System.Address;
54   --  This is the low level allocation routine. Given a size in storage
55   --  units, it returns the address of a maximally aligned block of
56   --  memory. The implementation of this routine is guaranteed to be
57   --  task safe, and also aborts are deferred if necessary.
58   --
59   --  If size_t is set to size_t'Last on entry, then a Storage_Error
60   --  exception is raised with a message "object too large".
61   --
62   --  If size_t is set to zero on entry, then a minimal (but non-zero)
63   --  size block is allocated.
64   --
65   --  Note: this is roughly equivalent to the standard C malloc call
66   --  with the additional semantics as described above.
67
68   procedure Free (Ptr : System.Address);
69   --  This is the low level free routine. It frees a block previously
70   --  allocated with a call to Alloc. As in the case of Alloc, this
71   --  call is guaranteed task safe, and aborts are deferred.
72   --
73   --  Note: this is roughly equivalent to the standard C free call
74   --  with the additional semantics as described above.
75
76   function Realloc
77     (Ptr  : System.Address;
78      Size : size_t)
79      return System.Address;
80   --  This is the low level reallocation routine. It takes an existing
81   --  block address returned by a previous call to Alloc or Realloc,
82   --  and reallocates the block. The size can either be increased or
83   --  decreased. If possible the reallocation is done in place, so that
84   --  the returned result is the same as the value of Ptr on entry.
85   --  However, it may be necessary to relocate the block to another
86   --  address, in which case the information is copied to the new
87   --  block, and the old block is freed. The implementation of this
88   --  routine is guaranteed to be task safe, and also aborts are
89   --  deferred as necessary.
90   --
91   --  If size_t is set to size_t'Last on entry, then a Storage_Error
92   --  exception is raised with a message "object too large".
93   --
94   --  If size_t is set to zero on entry, then a minimal (but non-zero)
95   --  size block is allocated.
96   --
97   --  Note: this is roughly equivalent to the standard C realloc call
98   --  with the additional semantics as described above.
99
100private
101
102   --  The following names are used from the generated compiler code
103
104   pragma Export (C, Alloc,   "__gnat_malloc");
105   pragma Export (C, Free,    "__gnat_free");
106   pragma Export (C, Realloc, "__gnat_realloc");
107
108end System.Memory;
109