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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --           A D A . C O N T A I N E R S . H A S H E D _ S E T S            --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2004-2009, 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 3,  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.                                     --
  21 --                                                                          --
  22 -- As a special exception under Section 7 of GPL version 3, you are granted --
  23 -- additional permissions described in the GCC Runtime Library Exception,   --
  24 -- version 3.1, as published by the Free Software Foundation.               --
  25 --                                                                          --
  26 -- You should have received a copy of the GNU General Public License and    --
  27 -- a copy of the GCC Runtime Library Exception along with this program;     --
  28 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  29 -- <http://www.gnu.org/licenses/>.                                          --
  30 --                                                                          --
  31 -- This unit was originally developed by Matthew J Heaney.                  --
  32 ------------------------------------------------------------------------------
  33
  34 private with Ada.Containers.Hash_Tables;
  35 private with Ada.Streams;
  36 private with Ada.Finalization;
  37
  38 generic
  39    type Element_Type is private;
  40
  41    with function Hash (Element : Element_Type) return Hash_Type;
  42
  43    with function Equivalent_Elements
  44           (Left, Right : Element_Type) return Boolean;
  45
  46    with function "=" (Left, Right : Element_Type) return Boolean is <>;
  47
  48 package Ada.Containers.Hashed_Sets is
  49    pragma Preelaborate;
  50    pragma Remote_Types;
  51
  52    type Set is tagged private;
  53    pragma Preelaborable_Initialization (Set);
  54
  55    type Cursor is private;
  56    pragma Preelaborable_Initialization (Cursor);
  57
  58    Empty_Set : constant Set;
  59    --  Set objects declared without an initialization expression are
  60    --  initialized to the value Empty_Set.
  61
  62    No_Element : constant Cursor;
  63    --  Cursor objects declared without an initialization expression are
  64    --  initialized to the value No_Element.
  65
  66    function "=" (Left, Right : Set) return Boolean;
  67    --  For each element in Left, set equality attempts to find the equal
  68    --  element in Right; if a search fails, then set equality immediately
  69    --  returns False. The search works by calling Hash to find the bucket in
  70    --  the Right set that corresponds to the Left element. If the bucket is
  71    --  non-empty, the search calls the generic formal element equality operator
  72    --  to compare the element (in Left) to the element of each node in the
  73    --  bucket (in Right); the search terminates when a matching node in the
  74    --  bucket is found, or the nodes in the bucket are exhausted. (Note that
  75    --  element equality is called here, not Equivalent_Elements. Set equality
  76    --  is the only operation in which element equality is used. Compare set
  77    --  equality to Equivalent_Sets, which does call Equivalent_Elements.)
  78
  79    function Equivalent_Sets (Left, Right : Set) return Boolean;
  80    --  Similar to set equality, with the difference that the element in Left is
  81    --  compared to the elements in Right using the generic formal
  82    --  Equivalent_Elements operation instead of element equality.
  83
  84    function To_Set (New_Item : Element_Type) return Set;
  85    --  Constructs a singleton set comprising New_Element. To_Set calls Hash to
  86    --  determine the bucket for New_Item.
  87
  88    function Capacity (Container : Set) return Count_Type;
  89    --  Returns the current capacity of the set. Capacity is the maximum length
  90    --  before which rehashing in guaranteed not to occur.
  91
  92    procedure Reserve_Capacity (Container : in out Set; Capacity : Count_Type);
  93    --  Adjusts the current capacity, by allocating a new buckets array. If the
  94    --  requested capacity is less than the current capacity, then the capacity
  95    --  is contracted (to a value not less than the current length). If the
  96    --  requested capacity is greater than the current capacity, then the
  97    --  capacity is expanded (to a value not less than what is requested). In
  98    --  either case, the nodes are rehashed from the old buckets array onto the
  99    --  new buckets array (Hash is called once for each existing element in
 100    --  order to compute the new index), and then the old buckets array is
 101    --  deallocated.
 102
 103    function Length (Container : Set) return Count_Type;
 104    --  Returns the number of items in the set
 105
 106    function Is_Empty (Container : Set) return Boolean;
 107    --  Equivalent to Length (Container) = 0
 108
 109    procedure Clear (Container : in out Set);
 110    --  Removes all of the items from the set
 111
 112    function Element (Position : Cursor) return Element_Type;
 113    --  Returns the element of the node designated by the cursor
 114
 115    procedure Replace_Element
 116      (Container : in out Set;
 117       Position  : Cursor;
 118       New_Item  : Element_Type);
 119    --  If New_Item is equivalent (as determined by calling Equivalent_Elements)
 120    --  to the element of the node designated by Position, then New_Element is
 121    --  assigned to that element. Otherwise, it calls Hash to determine the
 122    --  bucket for New_Item. If the bucket is not empty, then it calls
 123    --  Equivalent_Elements for each node in that bucket to determine whether
 124    --  New_Item is equivalent to an element in that bucket. If
 125    --  Equivalent_Elements returns True then Program_Error is raised (because
 126    --  an element may appear only once in the set); otherwise, New_Item is
 127    --  assigned to the node designated by Position, and the node is moved to
 128    --  its new bucket.
 129
 130    procedure Query_Element
 131      (Position : Cursor;
 132       Process  : not null access procedure (Element : Element_Type));
 133    --  Calls Process with the element (having only a constant view) of the node
 134    --  designed by the cursor.
 135
 136    procedure Move (Target : in out Set; Source : in out Set);
 137    --  Clears Target (if it's not empty), and then moves (not copies) the
 138    --  buckets array and nodes from Source to Target.
 139
 140    procedure Insert
 141      (Container : in out Set;
 142       New_Item  : Element_Type;
 143       Position  : out Cursor;
 144       Inserted  : out Boolean);
 145    --  Conditionally inserts New_Item into the set. If New_Item is already in
 146    --  the set, then Inserted returns False and Position designates the node
 147    --  containing the existing element (which is not modified). If New_Item is
 148    --  not already in the set, then Inserted returns True and Position
 149    --  designates the newly-inserted node containing New_Item. The search for
 150    --  an existing element works as follows. Hash is called to determine
 151    --  New_Item's bucket; if the bucket is non-empty, then Equivalent_Elements
 152    --  is called to compare New_Item to the element of each node in that
 153    --  bucket. If the bucket is empty, or there were no equivalent elements in
 154    --  the bucket, the search "fails" and the New_Item is inserted in the set
 155    --  (and Inserted returns True); otherwise, the search "succeeds" (and
 156    --  Inserted returns False).
 157
 158    procedure Insert  (Container : in out Set; New_Item : Element_Type);
 159    --  Attempts to insert New_Item into the set, performing the usual insertion
 160    --  search (which involves calling both Hash and Equivalent_Elements); if
 161    --  the search succeeds (New_Item is equivalent to an element already in the
 162    --  set, and so was not inserted), then this operation raises
 163    --  Constraint_Error. (This version of Insert is similar to Replace, but
 164    --  having the opposite exception behavior. It is intended for use when you
 165    --  want to assert that the item is not already in the set.)
 166
 167    procedure Include (Container : in out Set; New_Item : Element_Type);
 168    --  Attempts to insert New_Item into the set. If an element equivalent to
 169    --  New_Item is already in the set (the insertion search succeeded, and
 170    --  hence New_Item was not inserted), then the value of New_Item is assigned
 171    --  to the existing element. (This insertion operation only raises an
 172    --  exception if cursor tampering occurs. It is intended for use when you
 173    --  want to insert the item in the set, and you don't care whether an
 174    --  equivalent element is already present.)
 175
 176    procedure Replace (Container : in out Set; New_Item : Element_Type);
 177    --  Searches for New_Item in the set; if the search fails (because an
 178    --  equivalent element was not in the set), then it raises
 179    --  Constraint_Error. Otherwise, the existing element is assigned the value
 180    --  New_Item. (This is similar to Insert, but with the opposite exception
 181    --  behavior. It is intended for use when you want to assert that the item
 182    --  is already in the set.)
 183
 184    procedure Exclude (Container : in out Set; Item : Element_Type);
 185    --  Searches for Item in the set, and if found, removes its node from the
 186    --  set and then deallocates it. The search works as follows. The operation
 187    --  calls Hash to determine the item's bucket; if the bucket is not empty,
 188    --  it calls Equivalent_Elements to compare Item to the element of each node
 189    --  in the bucket. (This is the deletion analog of Include. It is intended
 190    --  for use when you want to remove the item from the set, but don't care
 191    --  whether the item is already in the set.)
 192
 193    procedure Delete  (Container : in out Set; Item : Element_Type);
 194    --  Searches for Item in the set (which involves calling both Hash and
 195    --  Equivalent_Elements). If the search fails, then the operation raises
 196    --  Constraint_Error. Otherwise it removes the node from the set and then
 197    --  deallocates it. (This is the deletion analog of non-conditional
 198    --  Insert. It is intended for use when you want to assert that the item is
 199    --  already in the set.)
 200
 201    procedure Delete (Container : in out Set; Position : in out Cursor);
 202    --  Removes the node designated by Position from the set, and then
 203    --  deallocates the node. The operation calls Hash to determine the bucket,
 204    --  and then compares Position to each node in the bucket until there's a
 205    --  match (it does not call Equivalent_Elements).
 206
 207    procedure Union (Target : in out Set; Source : Set);
 208    --  The operation first calls Reserve_Capacity if the current capacity is
 209    --  less than the sum of the lengths of Source and Target. It then iterates
 210    --  over the Source set, and conditionally inserts each element into Target.
 211
 212    function Union (Left, Right : Set) return Set;
 213    --  The operation first copies the Left set to the result, and then iterates
 214    --  over the Right set to conditionally insert each element into the result.
 215
 216    function "or" (Left, Right : Set) return Set renames Union;
 217
 218    procedure Intersection (Target : in out Set; Source : Set);
 219    --  Iterates over the Target set (calling First and Next), calling Find to
 220    --  determine whether the element is in Source. If an equivalent element is
 221    --  not found in Source, the element is deleted from Target.
 222
 223    function Intersection (Left, Right : Set) return Set;
 224    --  Iterates over the Left set, calling Find to determine whether the
 225    --  element is in Right. If an equivalent element is found, it is inserted
 226    --  into the result set.
 227
 228    function "and" (Left, Right : Set) return Set renames Intersection;
 229
 230    procedure Difference (Target : in out Set; Source : Set);
 231    --  Iterates over the Source (calling First and Next), calling Find to
 232    --  determine whether the element is in Target. If an equivalent element is
 233    --  found, it is deleted from Target.
 234
 235    function Difference (Left, Right : Set) return Set;
 236    --  Iterates over the Left set, calling Find to determine whether the
 237    --  element is in the Right set. If an equivalent element is not found, the
 238    --  element is inserted into the result set.
 239
 240    function "-" (Left, Right : Set) return Set renames Difference;
 241
 242    procedure Symmetric_Difference (Target : in out Set; Source : Set);
 243    --  The operation first calls Reserve_Capacity if the current capacity is
 244    --  less than the sum of the lengths of Source and Target. It then iterates
 245    --  over the Source set, searching for the element in Target (calling Hash
 246    --  and Equivalent_Elements). If an equivalent element is found, it is
 247    --  removed from Target; otherwise it is inserted into Target.
 248
 249    function Symmetric_Difference (Left, Right : Set) return Set;
 250    --  The operation first iterates over the Left set. It calls Find to
 251    --  determine whether the element is in the Right set. If no equivalent
 252    --  element is found, the element from Left is inserted into the result. The
 253    --  operation then iterates over the Right set, to determine whether the
 254    --  element is in the Left set. If no equivalent element is found, the Right
 255    --  element is inserted into the result.
 256
 257    function "xor" (Left, Right : Set) return Set
 258      renames Symmetric_Difference;
 259
 260    function Overlap (Left, Right : Set) return Boolean;
 261    --  Iterates over the Left set (calling First and Next), calling Find to
 262    --  determine whether the element is in the Right set. If an equivalent
 263    --  element is found, the operation immediately returns True. The operation
 264    --  returns False if the iteration over Left terminates without finding any
 265    --  equivalent element in Right.
 266
 267    function Is_Subset (Subset : Set; Of_Set : Set) return Boolean;
 268    --  Iterates over Subset (calling First and Next), calling Find to determine
 269    --  whether the element is in Of_Set. If no equivalent element is found in
 270    --  Of_Set, the operation immediately returns False. The operation returns
 271    --  True if the iteration over Subset terminates without finding an element
 272    --  not in Of_Set (that is, every element in Subset is equivalent to an
 273    --  element in Of_Set).
 274
 275    function First (Container : Set) return Cursor;
 276    --  Returns a cursor that designates the first non-empty bucket, by
 277    --  searching from the beginning of the buckets array.
 278
 279    function Next (Position : Cursor) return Cursor;
 280    --  Returns a cursor that designates the node that follows the current one
 281    --  designated by Position. If Position designates the last node in its
 282    --  bucket, the operation calls Hash to compute the index of this bucket,
 283    --  and searches the buckets array for the first non-empty bucket, starting
 284    --  from that index; otherwise, it simply follows the link to the next node
 285    --  in the same bucket.
 286
 287    procedure Next (Position : in out Cursor);
 288    --  Equivalent to Position := Next (Position)
 289
 290    function Find
 291      (Container : Set;
 292       Item      : Element_Type) return Cursor;
 293    --  Searches for Item in the set. Find calls Hash to determine the item's
 294    --  bucket; if the bucket is not empty, it calls Equivalent_Elements to
 295    --  compare Item to each element in the bucket. If the search succeeds, Find
 296    --  returns a cursor designating the node containing the equivalent element;
 297    --  otherwise, it returns No_Element.
 298
 299    function Contains (Container : Set; Item : Element_Type) return Boolean;
 300    --  Equivalent to Find (Container, Item) /= No_Element
 301
 302    function Has_Element (Position : Cursor) return Boolean;
 303    --  Equivalent to Position /= No_Element
 304
 305    function Equivalent_Elements (Left, Right : Cursor) return Boolean;
 306    --  Returns the result of calling Equivalent_Elements with the elements of
 307    --  the nodes designated by cursors Left and Right.
 308
 309    function Equivalent_Elements
 310      (Left  : Cursor;
 311       Right : Element_Type) return Boolean;
 312    --  Returns the result of calling Equivalent_Elements with element of the
 313    --  node designated by Left and element Right.
 314
 315    function Equivalent_Elements
 316      (Left  : Element_Type;
 317       Right : Cursor) return Boolean;
 318    --  Returns the result of calling Equivalent_Elements with element Left and
 319    --  the element of the node designated by Right.
 320
 321    procedure Iterate
 322      (Container : Set;
 323       Process   : not null access procedure (Position : Cursor));
 324    --  Calls Process for each node in the set
 325
 326    generic
 327       type Key_Type (<>) is private;
 328
 329       with function Key (Element : Element_Type) return Key_Type;
 330
 331       with function Hash (Key : Key_Type) return Hash_Type;
 332
 333       with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
 334
 335    package Generic_Keys is
 336
 337       function Key (Position : Cursor) return Key_Type;
 338       --  Applies generic formal operation Key to the element of the node
 339       --  designated by Position.
 340
 341       function Element (Container : Set; Key : Key_Type) return Element_Type;
 342       --  Searches (as per the key-based Find) for the node containing Key, and
 343       --  returns the associated element.
 344
 345       procedure Replace
 346         (Container : in out Set;
 347          Key       : Key_Type;
 348          New_Item  : Element_Type);
 349       --  Searches (as per the key-based Find) for the node containing Key, and
 350       --  then replaces the element of that node (as per the element-based
 351       --  Replace_Element).
 352
 353       procedure Exclude (Container : in out Set; Key : Key_Type);
 354       --  Searches for Key in the set, and if found, removes its node from the
 355       --  set and then deallocates it. The search works by first calling Hash
 356       --  (on Key) to determine the bucket; if the bucket is not empty, it
 357       --  calls Equivalent_Keys to compare parameter Key to the value of
 358       --  generic formal operation Key applied to element of each node in the
 359       --  bucket.
 360
 361       procedure Delete (Container : in out Set; Key : Key_Type);
 362       --  Deletes the node containing Key as per Exclude, with the difference
 363       --  that Constraint_Error is raised if Key is not found.
 364
 365       function Find (Container : Set; Key : Key_Type) return Cursor;
 366       --  Searches for the node containing Key, and returns a cursor
 367       --  designating the node. The search works by first calling Hash (on Key)
 368       --  to determine the bucket. If the bucket is not empty, the search
 369       --  compares Key to the element of each node in the bucket, and returns
 370       --  the matching node. The comparison itself works by applying the
 371       --  generic formal Key operation to the element of the node, and then
 372       --  calling generic formal operation Equivalent_Keys.
 373
 374       function Contains (Container : Set; Key : Key_Type) return Boolean;
 375       --  Equivalent to Find (Container, Key) /= No_Element
 376
 377       procedure Update_Element_Preserving_Key
 378         (Container : in out Set;
 379          Position  : Cursor;
 380          Process   : not null access
 381                        procedure (Element : in out Element_Type));
 382       --  Calls Process with the element of the node designated by Position,
 383       --  but with the restriction that the key-value of the element is not
 384       --  modified. The operation first makes a copy of the value returned by
 385       --  applying generic formal operation Key on the element of the node, and
 386       --  then calls Process with the element. The operation verifies that the
 387       --  key-part has not been modified by calling generic formal operation
 388       --  Equivalent_Keys to compare the saved key-value to the value returned
 389       --  by applying generic formal operation Key to the post-Process value of
 390       --  element. If the key values compare equal then the operation
 391       --  completes. Otherwise, the node is removed from the map and
 392       --  Program_Error is raised.
 393
 394    end Generic_Keys;
 395
 396 private
 397
 398    pragma Inline (Next);
 399
 400    type Node_Type;
 401    type Node_Access is access Node_Type;
 402
 403    type Node_Type is limited record
 404       Element : Element_Type;
 405       Next    : Node_Access;
 406    end record;
 407
 408    package HT_Types is
 409      new Hash_Tables.Generic_Hash_Table_Types (Node_Type, Node_Access);
 410
 411    type Set is new Ada.Finalization.Controlled with record
 412       HT : HT_Types.Hash_Table_Type;
 413    end record;
 414
 415    overriding
 416    procedure Adjust (Container : in out Set);
 417
 418    overriding
 419    procedure Finalize (Container : in out Set);
 420
 421    use HT_Types;
 422    use Ada.Finalization;
 423    use Ada.Streams;
 424
 425    type Set_Access is access all Set;
 426    for Set_Access'Storage_Size use 0;
 427
 428    type Cursor is record
 429       Container : Set_Access;
 430       Node      : Node_Access;
 431    end record;
 432
 433    procedure Write
 434      (Stream : not null access Root_Stream_Type'Class;
 435       Item   : Cursor);
 436
 437    for Cursor'Write use Write;
 438
 439    procedure Read
 440      (Stream : not null access Root_Stream_Type'Class;
 441       Item   : out Cursor);
 442
 443    for Cursor'Read use Read;
 444
 445    No_Element : constant Cursor := (Container => null, Node => null);
 446
 447    procedure Write
 448      (Stream    : not null access Root_Stream_Type'Class;
 449       Container : Set);
 450
 451    for Set'Write use Write;
 452
 453    procedure Read
 454      (Stream    : not null access Root_Stream_Type'Class;
 455       Container : out Set);
 456
 457    for Set'Read use Read;
 458
 459    Empty_Set : constant Set := (Controlled with HT => (null, 0, 0, 0));
 460
 461 end Ada.Containers.Hashed_Sets;