222 lines
7.6 KiB
Ada
222 lines
7.6 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- S Y S T E M . M E M O R Y --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 2001-2009, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This version provides ways to limit the amount of used memory for systems
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-- that do not have OS support for that.
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-- The amount of available memory available for dynamic allocation is limited
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-- by setting the environment variable GNAT_MEMORY_LIMIT to the number of
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-- kilobytes that can be used.
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--
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-- Windows is currently using this version.
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with Ada.Exceptions;
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with System.Soft_Links;
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package body System.Memory is
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use Ada.Exceptions;
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use System.Soft_Links;
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function c_malloc (Size : size_t) return System.Address;
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pragma Import (C, c_malloc, "malloc");
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procedure c_free (Ptr : System.Address);
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pragma Import (C, c_free, "free");
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function c_realloc
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(Ptr : System.Address; Size : size_t) return System.Address;
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pragma Import (C, c_realloc, "realloc");
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function msize (Ptr : System.Address) return size_t;
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pragma Import (C, msize, "_msize");
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function getenv (Str : String) return System.Address;
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pragma Import (C, getenv);
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function atoi (Str : System.Address) return Integer;
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pragma Import (C, atoi);
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Available_Memory : size_t := 0;
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-- Amount of memory that is available for heap allocations.
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-- A value of 0 means that the amount is not yet initialized.
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Msize_Accuracy : constant := 4096;
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-- Defines the amount of memory to add to requested allocation sizes,
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-- because malloc may return a bigger block than requested. As msize
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-- is used when by Free, it must be used on allocation as well. To
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-- prevent underflow of available_memory we need to use a reserve.
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procedure Check_Available_Memory (Size : size_t);
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-- This routine must be called while holding the task lock. When the
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-- memory limit is not yet initialized, it will be set to the value of
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-- the GNAT_MEMORY_LIMIT environment variable or to unlimited if that
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-- does not exist. If the size is larger than the amount of available
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-- memory, the task lock will be freed and a storage_error exception
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-- will be raised.
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-----------
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-- Alloc --
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-----------
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function Alloc (Size : size_t) return System.Address is
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Result : System.Address;
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Actual_Size : size_t := Size;
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begin
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if Size = size_t'Last then
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Raise_Exception (Storage_Error'Identity, "object too large");
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end if;
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-- Change size from zero to non-zero. We still want a proper pointer
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-- for the zero case because pointers to zero length objects have to
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-- be distinct, but we can't just go ahead and allocate zero bytes,
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-- since some malloc's return zero for a zero argument.
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if Size = 0 then
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Actual_Size := 1;
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end if;
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Lock_Task.all;
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if Actual_Size + Msize_Accuracy >= Available_Memory then
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Check_Available_Memory (Size + Msize_Accuracy);
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end if;
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Result := c_malloc (Actual_Size);
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if Result /= System.Null_Address then
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Available_Memory := Available_Memory - msize (Result);
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end if;
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Unlock_Task.all;
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if Result = System.Null_Address then
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Raise_Exception (Storage_Error'Identity, "heap exhausted");
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end if;
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return Result;
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end Alloc;
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----------------------------
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-- Check_Available_Memory --
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----------------------------
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procedure Check_Available_Memory (Size : size_t) is
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Gnat_Memory_Limit : System.Address;
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begin
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if Available_Memory = 0 then
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-- The amount of available memory hasn't been initialized yet
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Gnat_Memory_Limit := getenv ("GNAT_MEMORY_LIMIT" & ASCII.NUL);
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if Gnat_Memory_Limit /= System.Null_Address then
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Available_Memory :=
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size_t (atoi (Gnat_Memory_Limit)) * 1024 + Msize_Accuracy;
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else
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Available_Memory := size_t'Last;
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end if;
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end if;
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if Size >= Available_Memory then
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-- There is a memory overflow
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Unlock_Task.all;
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Raise_Exception
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(Storage_Error'Identity, "heap memory limit exceeded");
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end if;
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end Check_Available_Memory;
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----------
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-- Free --
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----------
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procedure Free (Ptr : System.Address) is
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begin
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Lock_Task.all;
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if Ptr /= System.Null_Address then
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Available_Memory := Available_Memory + msize (Ptr);
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end if;
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c_free (Ptr);
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Unlock_Task.all;
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end Free;
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-------------
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-- Realloc --
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-------------
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function Realloc
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(Ptr : System.Address;
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Size : size_t)
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return System.Address
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is
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Result : System.Address;
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Actual_Size : constant size_t := Size;
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Old_Size : size_t;
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begin
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if Size = size_t'Last then
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Raise_Exception (Storage_Error'Identity, "object too large");
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end if;
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Lock_Task.all;
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Old_Size := msize (Ptr);
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-- Conservative check - no need to try to be precise here
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if Size + Msize_Accuracy >= Available_Memory then
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Check_Available_Memory (Size + Msize_Accuracy);
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end if;
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Result := c_realloc (Ptr, Actual_Size);
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if Result /= System.Null_Address then
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Available_Memory := Available_Memory + Old_Size - msize (Result);
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end if;
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Unlock_Task.all;
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if Result = System.Null_Address then
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Raise_Exception (Storage_Error'Identity, "heap exhausted");
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end if;
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return Result;
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end Realloc;
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end System.Memory;
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