gcc/ada/a-chtgke.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                 ADA.CONTAINERS.HASH_TABLES.GENERIC_KEYS                  --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --             Copyright (C) 2004 Free Software Foundation, Inc.            --
  10 --                                                                          --
  11 -- This specification is derived from the Ada Reference Manual for use with --
  12 -- GNAT. The copyright notice above, and the license provisions that follow --
  13 -- apply solely to the  contents of the part following the private keyword. --
  14 --                                                                          --
  15 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  16 -- terms of the  GNU General Public License as published  by the Free Soft- --
  17 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  18 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  19 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  20 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  21 -- for  more details.  You should have  received  a copy of the GNU General --
  22 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  23 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  24 -- MA 02111-1307, USA.                                                      --
  25 --                                                                          --
  26 -- As a special exception,  if other files  instantiate  generics from this --
  27 -- unit, or you link  this unit with other files  to produce an executable, --
  28 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  29 -- covered  by the  GNU  General  Public  License.  This exception does not --
  30 -- however invalidate  any other reasons why  the executable file  might be --
  31 -- covered by the  GNU Public License.                                      --
  32 --                                                                          --
  33 -- This unit was originally developed by Matthew J Heaney.                  --
  34 ------------------------------------------------------------------------------
  35
  36 package body Ada.Containers.Hash_Tables.Generic_Keys is
  37
  38    --------------------------
  39    -- Delete_Key_Sans_Free --
  40    --------------------------
  41
  42    procedure Delete_Key_Sans_Free
  43      (HT   : in out HT_Type;
  44       Key  : Key_Type;
  45       X    : out Node_Access)
  46    is
  47       Indx : Hash_Type;
  48       Prev : Node_Access;
  49
  50    begin
  51       if HT.Length = 0 then
  52          X := Null_Node;
  53          return;
  54       end if;
  55
  56       Indx := Index (HT, Key);
  57       X := HT.Buckets (Indx);
  58
  59       if X = Null_Node then
  60          return;
  61       end if;
  62
  63       if Equivalent_Keys (Key, X) then
  64          HT.Buckets (Indx) := Next (X);
  65          HT.Length := HT.Length - 1;
  66          return;
  67       end if;
  68
  69       loop
  70          Prev := X;
  71          X := Next (Prev);
  72
  73          if X = Null_Node then
  74             return;
  75          end if;
  76
  77          if Equivalent_Keys (Key, X) then
  78             Set_Next (Node => Prev, Next => Next (X));
  79             HT.Length := HT.Length - 1;
  80             return;
  81          end if;
  82       end loop;
  83    end Delete_Key_Sans_Free;
  84
  85    ----------
  86    -- Find --
  87    ----------
  88
  89    function Find
  90      (HT  : HT_Type;
  91       Key : Key_Type) return Node_Access is
  92
  93       Indx : Hash_Type;
  94       Node : Node_Access;
  95
  96    begin
  97       if HT.Length = 0 then
  98          return Null_Node;
  99       end if;
 100
 101       Indx := Index (HT, Key);
 102
 103       Node := HT.Buckets (Indx);
 104       while Node /= Null_Node loop
 105          if Equivalent_Keys (Key, Node) then
 106             return Node;
 107          end if;
 108          Node := Next (Node);
 109       end loop;
 110
 111       return Null_Node;
 112    end Find;
 113
 114    --------------------------------
 115    -- Generic_Conditional_Insert --
 116    --------------------------------
 117
 118    procedure Generic_Conditional_Insert
 119      (HT      : in out HT_Type;
 120       Key     : Key_Type;
 121       Node    : out Node_Access;
 122       Success : out Boolean)
 123    is
 124       Indx : constant Hash_Type := Index (HT, Key);
 125       B    : Node_Access renames HT.Buckets (Indx);
 126
 127       subtype Length_Subtype is Count_Type range 0 .. Count_Type'Last - 1;
 128
 129    begin
 130       if B = Null_Node then
 131          declare
 132             Length : constant Length_Subtype := HT.Length;
 133          begin
 134             Node := New_Node (Next => Null_Node);
 135             Success := True;
 136
 137             B := Node;
 138             HT.Length := Length + 1;
 139          end;
 140
 141          return;
 142       end if;
 143
 144       Node := B;
 145       loop
 146          if Equivalent_Keys (Key, Node) then
 147             Success := False;
 148             return;
 149          end if;
 150
 151          Node := Next (Node);
 152
 153          exit when Node = Null_Node;
 154       end loop;
 155
 156       declare
 157          Length : constant Length_Subtype := HT.Length;
 158       begin
 159          Node := New_Node (Next => B);
 160          Success := True;
 161
 162          B := Node;
 163          HT.Length := Length + 1;
 164       end;
 165    end Generic_Conditional_Insert;
 166
 167    -----------
 168    -- Index --
 169    -----------
 170
 171    function Index
 172      (HT  : HT_Type;
 173       Key : Key_Type) return Hash_Type is
 174    begin
 175       return Hash (Key) mod HT.Buckets'Length;
 176    end Index;
 177
 178 end Ada.Containers.Hash_Tables.Generic_Keys;