gcc/ada/g-htable.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                          G N A T . H T A B L E                           --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --           Copyright (C) 1995-2002 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 --  Note: actual code is found in System.HTable (s-htable.ads/adb) since
  43 --  this facility is accessed from run time routines, but clients should
  44 --  always access the version supplied via GNAT.HTable.
  45
  46 with System.HTable;
  47
  48 package GNAT.HTable is
  49 pragma Preelaborate (HTable);
  50
  51 pragma Elaborate_Body;
  52 --  The elaborate body is because we have a dummy body to deal with bootstrap
  53 --  path problems (we used to have a real body, and now we don't need it any
  54 --  more, but the bootstrap requires that we have a dummy body, since otherwise
  55 --  the old body gets picked up.
  56
  57    -------------------
  58    -- Simple_HTable --
  59    -------------------
  60
  61    --  A simple hash table abstraction, easy to instantiate, easy to use.
  62    --  The table associates one element to one key with the procedure Set.
  63    --  Get retrieves the Element stored for a given Key. The efficiency of
  64    --  retrieval is function of the size of the Table parameterized by
  65    --  Header_Num and the hashing function Hash.
  66
  67    generic package Simple_HTable renames System.HTable.Simple_HTable;
  68
  69    --  For convenience of reference here is what this package has in it:
  70
  71    --  generic
  72    --     type Header_Num is range <>;
  73    --     --  An integer type indicating the number and range of hash headers
  74
  75    --     type Element is private;
  76    --     --  The type of element to be stored
  77
  78    --     No_Element : Element;
  79    --     --  The object that is returned by Get when no element has been set
  80    --     --  for a given key
  81
  82    --     type Key is private;
  83    --     with function Hash  (F : Key)      return Header_Num;
  84    --     with function Equal (F1, F2 : Key) return Boolean;
  85
  86    --  package Simple_HTable is
  87
  88    --     procedure Set (K : Key; E : Element);
  89    --     --  Associates an element with a given key. Overrides any previously
  90    --     --  associated element.
  91
  92    --     procedure Reset;
  93    --     --  Removes and frees all elements in the table
  94
  95    --     function Get (K : Key) return Element;
  96    --     --  Returns the Element associated with a key or No_Element if the
  97    --     --  given key has not associated element
  98
  99    --     procedure Remove (K : Key);
 100    --     --  Removes the latest inserted element pointer associated with the
 101    --     --  given key if any, does nothing if none.
 102
 103    --     function Get_First return Element;
 104    --     --  Returns No_Element if the HTable is empty, otherwise returns one
 105    --     --  non specified element. There is no guarantee that 2 calls to
 106    --     --  this function will return the same element.
 107
 108    --     function Get_Next return Element;
 109    --     --  Returns a non-specified element that has not been returned by the
 110    --     --  same function since the last call to Get_First or No_Element if
 111    --     --  there is no such element. If there is no call to 'Set' in between
 112    --     --  Get_Next calls, all the elements of the HTable will be traversed.
 113    --  end Simple_HTable;
 114
 115    -------------------
 116    -- Static_HTable --
 117    -------------------
 118
 119    --  A low-level Hash-Table abstraction, not as easy to instantiate as
 120    --  Simple_HTable but designed to allow complete control over the
 121    --  allocation of necessary data structures. Particularly useful when
 122    --  dynamic allocation is not desired. The model is that each Element
 123    --  contains its own Key that can be retrieved by Get_Key. Furthermore,
 124    --  Element provides a link that can be used by the HTable for linking
 125    --  elements with same hash codes:
 126
 127    --       Element
 128
 129    --         +-------------------+
 130    --         |       Key         |
 131    --         +-------------------+
 132    --         :    other data     :
 133    --         +-------------------+
 134    --         |     Next Elmt     |
 135    --         +-------------------+
 136
 137    generic package Static_HTable renames System.HTable.Static_HTable;
 138
 139    --  For convenience of reference here is what this package has in it:
 140
 141    --  generic
 142    --     type Header_Num is range <>;
 143    --     --  An integer type indicating the number and range of hash headers.
 144
 145    --     type Element (<>) is limited private;
 146    --     --  The type of element to be stored
 147
 148    --     type Elmt_Ptr is private;
 149    --     --  The type used to reference an element (will usually be an
 150    --     --  access type, but could be some other form of type such as
 151    --     --  an integer type).
 152
 153    --     Null_Ptr : Elmt_Ptr;
 154    --     --  The null value of the Elmt_Ptr type.
 155
 156    --     with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
 157    --     with function  Next     (E : Elmt_Ptr) return Elmt_Ptr;
 158    --     --  The type must provide an internal link for the sake of the
 159    --     --  staticness of the HTable.
 160
 161    --     type Key is limited private;
 162    --     with function Get_Key (E : Elmt_Ptr) return Key;
 163    --     with function Hash    (F : Key)      return Header_Num;
 164    --     with function Equal   (F1, F2 : Key) return Boolean;
 165
 166    --  package Static_HTable is
 167
 168    --     procedure Reset;
 169    --     --  Resets the hash table by setting all its elements to Null_Ptr.
 170    --     --  The effect is to clear the hash table so that it can be reused.
 171    --     --  For the most common case where Elmt_Ptr is an access type, and
 172    --     --  Null_Ptr is null, this is only needed if the same table is
 173    --     --  reused in a new context. If Elmt_Ptr is other than an access
 174    --     --  type, or Null_Ptr is other than null, then Reset must be called
 175    --     --  before the first use of the hash table.
 176
 177    --     procedure Set (E : Elmt_Ptr);
 178    --     --  Insert the element pointer in the HTable
 179
 180    --     function Get (K : Key) return Elmt_Ptr;
 181    --     --  Returns the latest inserted element pointer with the given Key
 182    --     --  or null if none.
 183
 184    --     procedure Remove (K : Key);
 185    --     --  Removes the latest inserted element pointer associated with the
 186    --     --  given key if any, does nothing if none.
 187
 188    --     function Get_First return Elmt_Ptr;
 189    --     --  Returns Null_Ptr if the HTable is empty, otherwise returns one
 190    --     --  non specified element. There is no guarantee that 2 calls to
 191    --     --  this function will return the same element.
 192
 193    --     function Get_Next return Elmt_Ptr;
 194    --     --  Returns a non-specified element that has not been returned by
 195    --     --  the same function since the last call to Get_First or Null_Ptr
 196    --     --  if there is no such element or Get_First has bever been called.
 197    --     --  If there is no call to 'Set' in between Get_Next calls, all
 198    --     --  the elements of the HTable will be traversed.
 199
 200    --  end Static_HTable;
 201
 202    ----------
 203    -- Hash --
 204    ----------
 205
 206    --  A generic hashing function working on String keys
 207
 208    generic function Hash renames System.HTable.Hash;
 209
 210    --  generic
 211    --     type Header_Num is range <>;
 212    --  function Hash (Key : String) return Header_Num;
 213
 214 end GNAT.HTable;