gcc/ada/libgnat/s-pooloc.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                    S Y S T E M . P O O L _ L O C A L                     --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2017, 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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with System.Memory;
  33
  34 with Ada.Unchecked_Conversion;
  35
  36 package body System.Pool_Local is
  37
  38    package SSE renames System.Storage_Elements;
  39    use type SSE.Storage_Offset;
  40
  41    Pointer_Size  : constant SSE.Storage_Offset := Address'Size / Storage_Unit;
  42    Pointers_Size : constant SSE.Storage_Offset := 2 * Pointer_Size;
  43
  44    type Acc_Address is access all Address;
  45    function To_Acc_Address is
  46      new Ada.Unchecked_Conversion (Address, Acc_Address);
  47
  48    -----------------------
  49    -- Local Subprograms --
  50    -----------------------
  51
  52    function Next (A : Address) return Acc_Address;
  53    pragma Inline (Next);
  54    --  Given an address of a block, return an access to the next block
  55
  56    function Prev (A : Address) return Acc_Address;
  57    pragma Inline (Prev);
  58    --  Given an address of a block, return an access to the previous block
  59
  60    --------------
  61    -- Allocate --
  62    --------------
  63
  64    procedure Allocate
  65      (Pool         : in out Unbounded_Reclaim_Pool;
  66       Address      : out System.Address;
  67       Storage_Size : SSE.Storage_Count;
  68       Alignment    : SSE.Storage_Count)
  69    is
  70       pragma Warnings (Off, Alignment);
  71
  72       Allocated : constant System.Address :=
  73                     Memory.Alloc
  74                       (Memory.size_t (Storage_Size + Pointers_Size));
  75
  76    begin
  77       --  The call to Alloc returns an address whose alignment is compatible
  78       --  with the worst case alignment requirement for the machine; thus the
  79       --  Alignment argument can be safely ignored.
  80
  81       if Allocated = Null_Address then
  82          raise Storage_Error;
  83       else
  84          Address := Allocated + Pointers_Size;
  85          Next (Allocated).all := Pool.First;
  86          Prev (Allocated).all := Null_Address;
  87
  88          if Pool.First /= Null_Address then
  89             Prev (Pool.First).all := Allocated;
  90          end if;
  91
  92          Pool.First := Allocated;
  93       end if;
  94    end Allocate;
  95
  96    ----------------
  97    -- Deallocate --
  98    ----------------
  99
 100    procedure Deallocate
 101      (Pool         : in out Unbounded_Reclaim_Pool;
 102       Address      : System.Address;
 103       Storage_Size : SSE.Storage_Count;
 104       Alignment    : SSE.Storage_Count)
 105    is
 106       pragma Warnings (Off, Storage_Size);
 107       pragma Warnings (Off, Alignment);
 108
 109       Allocated : constant System.Address := Address - Pointers_Size;
 110
 111    begin
 112       if Prev (Allocated).all = Null_Address then
 113          Pool.First := Next (Allocated).all;
 114
 115          --  Comment needed
 116
 117          if Pool.First /= Null_Address then
 118             Prev (Pool.First).all := Null_Address;
 119          end if;
 120       else
 121          Next (Prev (Allocated).all).all := Next (Allocated).all;
 122       end if;
 123
 124       if Next (Allocated).all /= Null_Address then
 125          Prev (Next (Allocated).all).all := Prev (Allocated).all;
 126       end if;
 127
 128       Memory.Free (Allocated);
 129    end Deallocate;
 130
 131    --------------
 132    -- Finalize --
 133    --------------
 134
 135    procedure Finalize (Pool : in out Unbounded_Reclaim_Pool) is
 136       N         : System.Address := Pool.First;
 137       Allocated : System.Address;
 138
 139    begin
 140       while N /= Null_Address loop
 141          Allocated := N;
 142          N := Next (N).all;
 143          Memory.Free (Allocated);
 144       end loop;
 145    end Finalize;
 146
 147    ----------
 148    -- Next --
 149    ----------
 150
 151    function Next (A : Address) return Acc_Address is
 152    begin
 153       return To_Acc_Address (A);
 154    end Next;
 155
 156    ----------
 157    -- Prev --
 158    ----------
 159
 160    function Prev (A : Address) return Acc_Address is
 161    begin
 162       return To_Acc_Address (A + Pointer_Size);
 163    end Prev;
 164
 165 end System.Pool_Local;