File : s-secsta.adb
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . S E C O N D A R Y _ S T A C K --
-- --
-- B o d y --
-- --
-- $Revision: 1.41 $
-- --
-- Copyright (C) 1992-1999 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, 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, --
-- 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. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
with System.Soft_Links;
with Unchecked_Conversion;
with Unchecked_Deallocation;
package body System.Secondary_Stack is
package TSL renames System.Soft_Links;
use type SSE.Storage_Offset;
-- +------------------+
-- | Next |
-- +------------------+
-- | | Last (200)
-- | |
-- | |
-- | |
-- | |
-- | |
-- | | First (101)
-- +------------------+
-- +----------> | | |
-- | +----------+-------+
-- | | |
-- | ^ V
-- | | |
-- | +-------+----------+
-- | | | |
-- | +------------------+
-- | | | Last (100)
-- | | C |
-- | | H |
-- +-----------------+ | +-------->| U |
-- | Current_Chunk -|--+ | | N |
-- +-----------------+ | | K |
-- | Top -|-----+ | | First (1)
-- +-----------------+ +------------------+
-- | Default_Size | | Prev |
-- +-----------------+ +------------------+
--
--
type Memory is array (Mark_Id range <>) of SSE.Storage_Element;
type Chunk_Id (First, Last : Mark_Id);
type Chunk_Ptr is access all Chunk_Id;
type Chunk_Id (First, Last : Mark_Id) is record
Prev, Next : Chunk_Ptr;
Mem : Memory (First .. Last);
end record;
type Stack_Id is record
Top : Mark_Id;
Current_Chunk : Chunk_Ptr;
Default_Size : SSE.Storage_Count;
end record;
type Stack_Ptr is access Stack_Id;
function From_Addr is new Unchecked_Conversion (Address, Stack_Ptr);
function To_Addr is new Unchecked_Conversion (Stack_Ptr, System.Address);
procedure Free is new Unchecked_Deallocation (Chunk_Id, Chunk_Ptr);
--------------
-- Allocate --
--------------
procedure SS_Allocate
(Address : out System.Address;
Storage_Size : SSE.Storage_Count)
is
Stack : constant Stack_Ptr :=
From_Addr (TSL.Get_Sec_Stack_Addr.all);
Chunk : Chunk_Ptr := Stack.Current_Chunk;
Max_Align : constant Mark_Id := Mark_Id (Standard'Maximum_Alignment);
Max_Size : constant Mark_Id :=
((Mark_Id (Storage_Size) + Max_Align - 1) / Max_Align)
* Max_Align;
Count_Unreleased_Chunks : Natural;
To_Be_Released_Chunk : Chunk_Ptr;
begin
-- The Current_Chunk may not be the good one if a lot of release
-- operations have taken place. So go down the stack if necessary
while Chunk.First > Stack.Top loop
Chunk := Chunk.Prev;
end loop;
-- Find out if the available memory in the current chunk is sufficient.
-- if not, go to the next one and eventally create the necessary room
Count_Unreleased_Chunks := 0;
while Chunk.Last - Stack.Top + 1 < Max_Size loop
if Chunk.Next /= null then
-- Release unused non-first empty chunk
if Chunk.Prev /= null and then Chunk.First = Stack.Top then
To_Be_Released_Chunk := Chunk;
Chunk := Chunk.Prev;
Chunk.Next := To_Be_Released_Chunk.Next;
To_Be_Released_Chunk.Next.Prev := Chunk;
Free (To_Be_Released_Chunk);
end if;
-- Create new chunk of the default size unless it is not sufficient
elsif SSE.Storage_Count (Max_Size) <= Stack.Default_Size then
Chunk.Next := new Chunk_Id (
First => Chunk.Last + 1,
Last => Chunk.Last + Mark_Id (Stack.Default_Size));
Chunk.Next.Prev := Chunk;
else
Chunk.Next := new Chunk_Id (
First => Chunk.Last + 1,
Last => Chunk.Last + Max_Size);
Chunk.Next.Prev := Chunk;
end if;
Chunk := Chunk.Next;
Stack.Top := Chunk.First;
end loop;
-- Resulting address is the address pointed by Stack.Top
Address := Chunk.Mem (Stack.Top)'Address;
Stack.Top := Stack.Top + Mark_Id (Max_Size);
Stack.Current_Chunk := Chunk;
end SS_Allocate;
-------------
-- SS_Init --
-------------
procedure SS_Init (Stk : out System.Address; Size : Natural) is
Stack : Stack_Ptr;
begin
Stack := new Stack_Id;
Stack.Current_Chunk := new Chunk_Id (1, Mark_Id (Size));
Stack.Top := 1;
Stack.Default_Size := SSE.Storage_Count (Size);
Stk := To_Addr (Stack);
end SS_Init;
-------------
-- SS_Free --
-------------
procedure SS_Free (Stk : System.Address) is
Stack : Stack_Ptr := From_Addr (Stk);
Chunk : Chunk_Ptr := Stack.Current_Chunk;
procedure Free is new Unchecked_Deallocation (Stack_Id, Stack_Ptr);
begin
while Chunk.Prev /= null loop
Chunk := Chunk.Prev;
end loop;
while Chunk.Next /= null loop
Chunk := Chunk.Next;
Free (Chunk.Prev);
end loop;
Free (Chunk);
Free (Stack);
end SS_Free;
-------------
-- SS_Mark --
-------------
function SS_Mark return Mark_Id is
begin
return From_Addr (TSL.Get_Sec_Stack_Addr.all).Top;
end SS_Mark;
----------------
-- SS_Release --
----------------
procedure SS_Release (M : Mark_Id) is
begin
From_Addr (TSL.Get_Sec_Stack_Addr.all).Top := M;
end SS_Release;
-------------
-- SS_Info --
-------------
procedure SS_Info is
Stack : constant Stack_Ptr :=
From_Addr (TSL.Get_Sec_Stack_Addr.all);
Nb_Chunks : Integer := 1;
Chunk : Chunk_Ptr := Stack.Current_Chunk;
begin
Put_Line ("Secondary Stack information:");
while Chunk.Prev /= null loop
Chunk := Chunk.Prev;
end loop;
while Chunk.Next /= null loop
Nb_Chunks := Nb_Chunks + 1;
Chunk := Chunk.Next;
end loop;
-- Current Chunk information
Put_Line (
" Total size : "
& Mark_Id'Image (Chunk.Last)
& " bytes");
Put_Line (
" Current allocated space : "
& Mark_Id'Image (Stack.Top - 1)
& " bytes");
Put_Line (
" Number of Chunks : "
& Integer'Image (Nb_Chunks));
Put_Line (
" Default size of Chunks : "
& SSE.Storage_Count'Image (Stack.Default_Size));
end SS_Info;
Default_Size : constant := 10 * 1024;
-- Allocate a secondary stack for the main program to use.
-- We make sure that the stack has maximum alignment. Some systems require
-- this (e.g. Sun), and in any case it is a good idea for efficiency.
Stack : aliased Stack_Id;
for Stack'Alignment use Standard'Maximum_Alignment;
Chunk : aliased Chunk_Id (1, Default_Size);
for Chunk'Alignment use Standard'Maximum_Alignment;
begin
Stack.Top := 1;
Stack.Current_Chunk := Chunk'Access;
Stack.Default_Size := Default_Size;
System.Soft_Links.Set_Sec_Stack_Addr_NT (Stack'Address);
end System.Secondary_Stack;