gcc/ada/g-dynhta.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                 G N A T . D Y N A M I C _ H T A B L E S                  --
   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 --  This package provides a facility similar to that of GNAT.HTable, except
  43 --  that this package declares types that can be used to define dynamic
  44 --  instances of hash tables, while instantiations in GNAT.HTable creates a
  45 --  single instance of the hash table.
  46
  47 --  Note that this interface should remain synchronized with those in
  48 --  GNAT.HTable to keep as much coherency as possible between these two
  49 --  related units.
  50
  51 with Ada.Unchecked_Deallocation;
  52 package GNAT.Dynamic_HTables is
  53
  54    -------------------
  55    -- Static_HTable --
  56    -------------------
  57
  58    --  A low-level Hash-Table abstraction, not as easy to instantiate as
  59    --  Simple_HTable but designed to allow complete control over the
  60    --  allocation of necessary data structures. Particularly useful when
  61    --  dynamic allocation is not desired. The model is that each Element
  62    --  contains its own Key that can be retrieved by Get_Key. Furthermore,
  63    --  Element provides a link that can be used by the HTable for linking
  64    --  elements with same hash codes:
  65
  66    --       Element
  67
  68    --         +-------------------+
  69    --         |       Key         |
  70    --         +-------------------+
  71    --         :    other data     :
  72    --         +-------------------+
  73    --         |     Next Elmt     |
  74    --         +-------------------+
  75
  76    generic
  77       type Header_Num is range <>;
  78       --  An integer type indicating the number and range of hash headers.
  79
  80       type Element (<>) is limited private;
  81       --  The type of element to be stored
  82
  83       type Elmt_Ptr is private;
  84       --  The type used to reference an element (will usually be an access
  85       --  type, but could be some other form of type such as an integer type).
  86
  87       Null_Ptr : Elmt_Ptr;
  88       --  The null value of the Elmt_Ptr type.
  89
  90       with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
  91       with function  Next     (E : Elmt_Ptr) return Elmt_Ptr;
  92       --  The type must provide an internal link for the sake of the
  93       --  staticness of the HTable.
  94
  95       type Key is limited private;
  96       with function Get_Key (E : Elmt_Ptr) return Key;
  97       with function Hash    (F : Key)      return Header_Num;
  98       with function Equal   (F1, F2 : Key) return Boolean;
  99
 100    package Static_HTable is
 101
 102       type Instance is private;
 103       Nil : constant Instance;
 104
 105       procedure Reset (T : in out Instance);
 106       --  Resets the hash table by setting all its elements to Null_Ptr. The
 107       --  effect is to clear the hash table so that it can be reused. For the
 108       --  most common case where Elmt_Ptr is an access type, and Null_Ptr is
 109       --  null, this is only needed if the same table is reused in a new
 110       --  context. If Elmt_Ptr is other than an access type, or Null_Ptr is
 111       --  other than null, then Reset must be called before the first use
 112       --  of the hash table.
 113
 114       procedure Set (T : in out Instance; E : Elmt_Ptr);
 115       --  Insert the element pointer in the HTable
 116
 117       function Get (T : Instance; K : Key) return Elmt_Ptr;
 118       --  Returns the latest inserted element pointer with the given Key
 119       --  or null if none.
 120
 121       procedure Remove (T : Instance; K : Key);
 122       --  Removes the latest inserted element pointer associated with the
 123       --  given key if any, does nothing if none.
 124
 125       function Get_First (T : Instance) return Elmt_Ptr;
 126       --  Returns Null_Ptr if the Htable is empty, otherwise returns one
 127       --  non specified element. There is no guarantee that 2 calls to this
 128       --  function will return the same element.
 129
 130       function Get_Next (T : Instance) return Elmt_Ptr;
 131       --  Returns a non-specified element that has not been returned by the
 132       --  same function since the last call to Get_First or Null_Ptr if
 133       --  there is no such element or Get_First has bever been called. If
 134       --  there is no call to 'Set' in between Get_Next calls, all the
 135       --  elements of the Htable will be traversed.
 136
 137    private
 138
 139       type Instance_Data;
 140       type Instance is access all Instance_Data;
 141       Nil : constant Instance := null;
 142
 143    end Static_HTable;
 144
 145    -------------------
 146    -- Simple_HTable --
 147    -------------------
 148
 149    --  A simple hash table abstraction, easy to instantiate, easy to use.
 150    --  The table associates one element to one key with the procedure Set.
 151    --  Get retrieves the Element stored for a given Key. The efficiency of
 152    --  retrieval is function of the size of the Table parameterized by
 153    --  Header_Num and the hashing function Hash.
 154
 155    generic
 156       type Header_Num is range <>;
 157       --  An integer type indicating the number and range of hash headers.
 158
 159       type Element is private;
 160       --  The type of element to be stored
 161
 162       No_Element : Element;
 163       --  The object that is returned by Get when no element has been set for
 164       --  a given key
 165
 166       type Key is private;
 167       with function Hash  (F : Key)      return Header_Num;
 168       with function Equal (F1, F2 : Key) return Boolean;
 169
 170    package Simple_HTable is
 171
 172       type Instance is private;
 173       Nil : constant Instance;
 174
 175       procedure Set (T : in out Instance; K : Key; E : Element);
 176       --  Associates an element with a given key. Overrides any previously
 177       --  associated element.
 178
 179       procedure Reset (T : in out Instance);
 180       --  Removes and frees all elements in the table
 181
 182       function Get (T : Instance; K : Key) return Element;
 183       --  Returns the Element associated with a key or No_Element if the
 184       --  given key has not associated element
 185
 186       procedure Remove (T : Instance; K : Key);
 187       --  Removes the latest inserted element pointer associated with the
 188       --  given key if any, does nothing if none.
 189
 190       function Get_First (T : Instance) return Element;
 191       --  Returns No_Element if the Htable is empty, otherwise returns one
 192       --  non specified element. There is no guarantee that two calls to this
 193       --  function will return the same element, if the Htable has been
 194       --  modified between the two calls.
 195
 196       function Get_Next (T : Instance) return Element;
 197       --  Returns a non-specified element that has not been returned by the
 198       --  same function since the last call to Get_First or No_Element if
 199       --  there is no such element. If there is no call to 'Set' in between
 200       --  Get_Next calls, all the elements of the Htable will be traversed.
 201       --  To guarantee that all the elements of the Htable will be traversed,
 202       --  no modification of the Htable (Set, Reset, Remove) should occur
 203       --  between a call to Get_First and subsequent consecutive calls to
 204       --  Get_Next, until one of these calls returns No_Element.
 205
 206    private
 207
 208       type Element_Wrapper;
 209       type Elmt_Ptr is access all Element_Wrapper;
 210       type Element_Wrapper is record
 211          K    : Key;
 212          E    : Element;
 213          Next : Elmt_Ptr;
 214       end record;
 215
 216       procedure Free is new
 217         Ada.Unchecked_Deallocation (Element_Wrapper, Elmt_Ptr);
 218
 219       procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
 220       function  Next     (E : Elmt_Ptr) return Elmt_Ptr;
 221       function  Get_Key  (E : Elmt_Ptr) return Key;
 222
 223       package Tab is new Static_HTable
 224         (Header_Num => Header_Num,
 225          Element    => Element_Wrapper,
 226          Elmt_Ptr   => Elmt_Ptr,
 227          Null_Ptr   => null,
 228          Set_Next   => Set_Next,
 229          Next       => Next,
 230          Key        => Key,
 231          Get_Key    => Get_Key,
 232          Hash       => Hash,
 233          Equal      => Equal);
 234
 235       type Instance is new Tab.Instance;
 236       Nil : constant Instance := Instance (Tab.Nil);
 237
 238    end Simple_HTable;
 239
 240 end GNAT.Dynamic_HTables;