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1996-09-28
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------------------------------------------------------------------------------
-- --
-- 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: 1.24 $ --
-- --
-- Copyright (c) 1992,1993,1994 NYU, All Rights Reserved --
-- --
-- The GNAT library is free software; you can redistribute it and/or modify --
-- it under terms of the GNU Library General Public License as published by --
-- the Free Software Foundation; either version 2, or (at your option) any --
-- later version. The GNAT library is distributed in the hope that it will --
-- be useful, but WITHOUT ANY WARRANTY; without even the implied warranty --
-- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU --
-- Library General Public License for more details. You should have --
-- received a copy of the GNU Library General Public License along with --
-- the GNAT library; see the file COPYING.LIB. If not, write to the Free --
-- Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. --
-- --
------------------------------------------------------------------------------
with System.Task_Specific_Data;
with System.Tasking_Soft_Links;
with Unchecked_Conversion;
with Unchecked_Deallocation;
package body System.Secondary_Stack is
-- +------------------+
-- | 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 Storage_Element;
type Chunk_Id (First, Last : Mark_Id);
type Chunk_Ptr is access 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 : 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);
------------------
-- Storage_Size --
------------------
function Storage_Size (Pool : Secondary_Stack_Pool) return Storage_Count is
Stack : constant Stack_Ptr
:= From_Addr (System.Task_Specific_Data.Get_Sec_Stack_Addr);
Chunk : Chunk_Ptr := Stack.Current_Chunk;
begin
while Chunk.Next /= null loop
Chunk := Chunk.Next;
end loop;
return Storage_Count (Chunk.Last);
end Storage_Size;
--------------
-- Allocate --
--------------
procedure Allocate
(Pool : in out Secondary_Stack_Pool;
Address : out System.Address;
Storage_Size : Storage_Count;
Alignment : Storage_Count)
is
Stack : constant Stack_Ptr :=
From_Addr
(System.Task_Specific_Data.Get_Sec_Stack_Addr);
Chunk : Chunk_Ptr := Stack.Current_Chunk;
Max_Size : constant Mark_Id := Mark_Id (Storage_Size + Alignment);
Align_Offset : Storage_Count;
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
while Chunk.Last - Stack.Top + 1 < Max_Size loop
if Chunk.Next /= null then
Chunk := Chunk.Next;
-- Create new chunk of the default size unless it is not sufficient
elsif 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;
Stack.Top := Chunk.First;
end loop;
-- Resulting address is the address pointed by Stack.Top
Address := Chunk.Mem (Stack.Top)'Address;
Align_Offset := Address mod Alignment;
Stack.Top := Stack.Top + Mark_Id (Storage_Size);
if Align_Offset /= 0 then
Address := Address + Alignment - Align_Offset;
Stack.Top := Stack.Top + Mark_Id (Alignment - Align_Offset);
end if;
Stack.Current_Chunk := Chunk;
end Allocate;
----------------
-- Deallocate --
----------------
-- Nothing to do, since space is released by an unmark operation
procedure Deallocate
(Pool : in out Secondary_Stack_Pool;
Address : System.Address;
Storage_Size : Storage_Count;
Alignment : Storage_Count)
is
begin
null;
end Deallocate;
-------------
-- 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 := 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);
procedure Free is new Unchecked_Deallocation (Chunk_Id, Chunk_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 (System.Task_Specific_Data.Get_Sec_Stack_Addr).Top;
end SS_Mark;
----------------
-- SS_Release --
----------------
procedure SS_Release (M : Mark_Id) is
begin
From_Addr (System.Task_Specific_Data.Get_Sec_Stack_Addr).Top := M;
end SS_Release;
-------------
-- SS_Info --
-------------
procedure SS_Info is
Stack : constant Stack_Ptr :=
From_Addr
(System.Task_Specific_Data.Get_Sec_Stack_Addr);
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 : "
& Storage_Count'Image (Stack.Default_Size));
end SS_Info;
begin
System.Tasking_Soft_Links.SS_Init := SS_Init'Access;
System.Tasking_Soft_Links.SS_Free := SS_Free'Access;
end System.Secondary_Stack;
