File : s-memory.adb
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
5 -- S Y S T E M . M E M O R Y --
-- --
-- S p e c --
-- --
-- $Revision: 1.3 $
10 -- --
-- Copyright (C) 2001 Free Software Foundation, Inc. --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
15 -- apply solely to the contents of the part following the private keyword. --
-- --
-- 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- --
20 -- 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 --
25 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, 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, --
30 -- 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. --
-- --
35 -- GNAT was originally developed by the GNAT team at New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
40 -- This version provides ways to limit the amount of used memory for systems
-- that do not have OS support for that.
-- The amount of available memory available for dynamic allocation is limited
-- by setting the environment variable GNAT_MEMORY_LIMIT to the number of
45 -- kilobytes that can be used.
--
-- Windows is currently using this version.
with Ada.Exceptions;
50 with System.Soft_Links;
package body System.Memory is
use Ada.Exceptions;
55 use System.Soft_Links;
function c_malloc (Size : size_t) return System.Address;
pragma Import (C, c_malloc, "malloc");
60 procedure c_free (Ptr : System.Address);
pragma Import (C, c_free, "free");
function c_realloc
(Ptr : System.Address; Size : size_t) return System.Address;
65 pragma Import (C, c_realloc, "realloc");
function msize (Ptr : System.Address) return size_t;
pragma Import (C, msize, "_msize");
70 function getenv (Str : String) return System.Address;
pragma Import (C, getenv);
function atoi (Str : System.Address) return Integer;
pragma Import (C, atoi);
75
Available_Memory : size_t := 0;
-- Amount of memory that is available for heap allocations.
-- A value of 0 means that the amount is not yet initialized.
80 Msize_Accuracy : constant := 4096;
-- Defines the amount of memory to add to requested allocation sizes,
-- because malloc may return a bigger block than requested. As msize
-- is used when by Free, it must be used on allocation as well. To
-- prevent underflow of available_memory we need to use a reserve.
85
procedure Check_Available_Memory (Size : size_t);
-- This routine must be called while holding the task lock. When the
-- memory limit is not yet initialized, it will be set to the value of
-- the GNAT_MEMORY_LIMIT environment variable or to unlimited if that
90 -- does not exist. If the size is larger than the amount of available
-- memory, the task lock will be freed and a storage_error exception
-- will be raised.
-----------
95 -- Alloc --
-----------
function Alloc (Size : size_t) return System.Address is
Result : System.Address;
100 Actual_Size : size_t := Size;
begin
if Size = size_t'Last then
Raise_Exception (Storage_Error'Identity, "object too large");
105 end if;
-- Change size from zero to non-zero. We still want a proper pointer
-- for the zero case because pointers to zero length objects have to
-- be distinct, but we can't just go ahead and allocate zero bytes,
110 -- since some malloc's return zero for a zero argument.
if Size = 0 then
Actual_Size := 1;
end if;
115
Lock_Task.all;
if Actual_Size + Msize_Accuracy >= Available_Memory then
Check_Available_Memory (Size + Msize_Accuracy);
120 end if;
Result := c_malloc (Actual_Size);
if Result /= System.Null_Address then
125 Available_Memory := Available_Memory - msize (Result);
end if;
Unlock_Task.all;
130 if Result = System.Null_Address then
Raise_Exception (Storage_Error'Identity, "heap exhausted");
end if;
return Result;
135 end Alloc;
----------------------------
-- Check_Available_Memory --
----------------------------
140
procedure Check_Available_Memory (Size : size_t) is
Gnat_Memory_Limit : System.Address;
begin
145 if Available_Memory = 0 then
-- The amount of available memory hasn't been initialized yet
Gnat_Memory_Limit := getenv ("GNAT_MEMORY_LIMIT" & ASCII.NUL);
150
if Gnat_Memory_Limit /= System.Null_Address then
Available_Memory :=
size_t (atoi (Gnat_Memory_Limit)) * 1024 + Msize_Accuracy;
else
155 Available_Memory := size_t'Last;
end if;
end if;
if Size >= Available_Memory then
160
-- There is a memory overflow
Unlock_Task.all;
Raise_Exception
165 (Storage_Error'Identity, "heap memory limit exceeded");
end if;
end Check_Available_Memory;
----------
170 -- Free --
----------
procedure Free (Ptr : System.Address) is
begin
175 Lock_Task.all;
if Ptr /= System.Null_Address then
Available_Memory := Available_Memory + msize (Ptr);
end if;
180
c_free (Ptr);
Unlock_Task.all;
end Free;
185
-------------
-- Realloc --
-------------
190 function Realloc
(Ptr : System.Address;
Size : size_t)
return System.Address
is
195 Result : System.Address;
Actual_Size : size_t := Size;
Old_Size : size_t;
begin
200 if Size = size_t'Last then
Raise_Exception (Storage_Error'Identity, "object too large");
end if;
Lock_Task.all;
205
Old_Size := msize (Ptr);
-- Conservative check - no need to try to be precise here
210 if Size + Msize_Accuracy >= Available_Memory then
Check_Available_Memory (Size + Msize_Accuracy);
end if;
Result := c_realloc (Ptr, Actual_Size);
215
if Result /= System.Null_Address then
Available_Memory := Available_Memory + Old_Size - msize (Result);
end if;
220 Unlock_Task.all;
if Result = System.Null_Address then
Raise_Exception (Storage_Error'Identity, "heap exhausted");
end if;
225
return Result;
end Realloc;
end System.Memory;