gcc/ada/s-memory.ads

   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
  45 package 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
 100 private
 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
 108 end System.Memory;