gcc/ada/s-htable.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                        S Y S T E M . H T A B L E                         --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --           Copyright (C) 1995-2003 Ada Core Technologies, 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  Hash table searching routines
  35
  36 --  This package contains two separate packages. The Simple_HTable package
  37 --  provides a very simple abstraction that associates one element to one
  38 --  key value and takes care of all allocations automatically using the heap.
  39 --  The Static_HTable package provides a more complex interface that allows
  40 --  complete control over allocation.
  41
  42 package System.HTable is
  43 pragma Preelaborate (HTable);
  44
  45    -------------------
  46    -- Simple_HTable --
  47    -------------------
  48
  49    --  A simple hash table abstraction, easy to instantiate, easy to use.
  50    --  The table associates one element to one key with the procedure Set.
  51    --  Get retrieves the Element stored for a given Key. The efficiency of
  52    --  retrieval is function of the size of the Table parameterized by
  53    --  Header_Num and the hashing function Hash.
  54
  55    generic
  56       type Header_Num is range <>;
  57       --  An integer type indicating the number and range of hash headers.
  58
  59       type Element is private;
  60       --  The type of element to be stored
  61
  62       No_Element : Element;
  63       --  The object that is returned by Get when no element has been set for
  64       --  a given key
  65
  66       type Key is private;
  67       with function Hash  (F : Key)      return Header_Num;
  68       with function Equal (F1, F2 : Key) return Boolean;
  69
  70    package Simple_HTable is
  71
  72       procedure Set (K : Key; E : Element);
  73       --  Associates an element with a given key. Overrides any previously
  74       --  associated element.
  75
  76       procedure Reset;
  77       --  Removes and frees all elements in the table
  78
  79       function Get (K : Key) return Element;
  80       --  Returns the Element associated with a key or No_Element if the
  81       --  given key has not associated element
  82
  83       procedure Remove (K : Key);
  84       --  Removes the latest inserted element pointer associated with the
  85       --  given key if any, does nothing if none.
  86
  87       function Get_First return Element;
  88       --  Returns No_Element if the HTable is empty, otherwise returns one
  89       --  non specified element. There is no guarantee that 2 calls to this
  90       --  function will return the same element.
  91
  92       function Get_Next return Element;
  93       --  Returns a non-specified element that has not been returned by the
  94       --  same function since the last call to Get_First or No_Element if
  95       --  there is no such element. If there is no call to 'Set' in between
  96       --  Get_Next calls, all the elements of the HTable will be traversed.
  97    end Simple_HTable;
  98
  99    -------------------
 100    -- Static_HTable --
 101    -------------------
 102
 103    --  A low-level Hash-Table abstraction, not as easy to instantiate as
 104    --  Simple_HTable but designed to allow complete control over the
 105    --  allocation of necessary data structures. Particularly useful when
 106    --  dynamic allocation is not desired. The model is that each Element
 107    --  contains its own Key that can be retrieved by Get_Key. Furthermore,
 108    --  Element provides a link that can be used by the HTable for linking
 109    --  elements with same hash codes:
 110
 111    --       Element
 112
 113    --         +-------------------+
 114    --         |       Key         |
 115    --         +-------------------+
 116    --         :    other data     :
 117    --         +-------------------+
 118    --         |     Next Elmt     |
 119    --         +-------------------+
 120
 121    generic
 122       type Header_Num is range <>;
 123       --  An integer type indicating the number and range of hash headers.
 124
 125       type Element (<>) is limited private;
 126       --  The type of element to be stored. This is historically part of the
 127       --  interface, even though it is not used at all in the operations of
 128       --  the package.
 129
 130       pragma Warnings (Off, Element);
 131       --  We have to kill warnings here, because Element is and always
 132       --  has been unreferenced, but we cannot remove it at this stage,
 133       --  since this unit is in wide use, and it certainly seems harmless.
 134
 135       type Elmt_Ptr is private;
 136       --  The type used to reference an element (will usually be an access
 137       --  type, but could be some other form of type such as an integer type).
 138
 139       Null_Ptr : Elmt_Ptr;
 140       --  The null value of the Elmt_Ptr type.
 141
 142       with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
 143       with function  Next     (E : Elmt_Ptr) return Elmt_Ptr;
 144       --  The type must provide an internal link for the sake of the
 145       --  staticness of the HTable.
 146
 147       type Key is limited private;
 148       with function Get_Key (E : Elmt_Ptr) return Key;
 149       with function Hash    (F : Key)      return Header_Num;
 150       with function Equal   (F1, F2 : Key) return Boolean;
 151
 152    package Static_HTable is
 153
 154       procedure Reset;
 155       --  Resets the hash table by setting all its elements to Null_Ptr. The
 156       --  effect is to clear the hash table so that it can be reused. For the
 157       --  most common case where Elmt_Ptr is an access type, and Null_Ptr is
 158       --  null, this is only needed if the same table is reused in a new
 159       --  context. If Elmt_Ptr is other than an access type, or Null_Ptr is
 160       --  other than null, then Reset must be called before the first use
 161       --  of the hash table.
 162
 163       procedure Set (E : Elmt_Ptr);
 164       --  Insert the element pointer in the HTable
 165
 166       function Get (K : Key) return Elmt_Ptr;
 167       --  Returns the latest inserted element pointer with the given Key
 168       --  or null if none.
 169
 170       procedure Remove (K : Key);
 171       --  Removes the latest inserted element pointer associated with the
 172       --  given key if any, does nothing if none.
 173
 174       function Get_First return Elmt_Ptr;
 175       --  Returns Null_Ptr if the HTable is empty, otherwise returns one
 176       --  non specified element. There is no guarantee that 2 calls to this
 177       --  function will return the same element.
 178
 179       function Get_Next return Elmt_Ptr;
 180       --  Returns a non-specified element that has not been returned by the
 181       --  same function since the last call to Get_First or Null_Ptr if
 182       --  there is no such element or Get_First has bever been called. If
 183       --  there is no call to 'Set' in between Get_Next calls, all the
 184       --  elements of the HTable will be traversed.
 185
 186    end Static_HTable;
 187
 188    ----------
 189    -- Hash --
 190    ----------
 191
 192    --  A generic hashing function working on String keys
 193
 194    generic
 195       type Header_Num is range <>;
 196    function Hash (Key : String) return Header_Num;
 197
 198 end System.HTable;