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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 . B O U N D E D _ H A S H E D _ S E T S   --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2004-2013, 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 with Ada.Iterator_Interfaces;
  35
  36 private with Ada.Containers.Hash_Tables;
  37 private with Ada.Streams;
  38 private with Ada.Finalization; use Ada.Finalization;
  39
  40 generic
  41    type Element_Type is private;
  42
  43    with function Hash (Element : Element_Type) return Hash_Type;
  44
  45    with function Equivalent_Elements
  46           (Left, Right : Element_Type) return Boolean;
  47
  48    with function "=" (Left, Right : Element_Type) return Boolean is <>;
  49
  50 package Ada.Containers.Bounded_Hashed_Sets is
  51    pragma Pure;
  52    pragma Remote_Types;
  53
  54    type Set (Capacity : Count_Type; Modulus : Hash_Type) is tagged private
  55      with Constant_Indexing => Constant_Reference,
  56           Default_Iterator  => Iterate,
  57           Iterator_Element  => Element_Type;
  58
  59    pragma Preelaborable_Initialization (Set);
  60
  61    type Cursor is private;
  62    pragma Preelaborable_Initialization (Cursor);
  63
  64    Empty_Set : constant Set;
  65    --  Set objects declared without an initialization expression are
  66    --  initialized to the value Empty_Set.
  67
  68    No_Element : constant Cursor;
  69    --  Cursor objects declared without an initialization expression are
  70    --  initialized to the value No_Element.
  71
  72    function Has_Element (Position : Cursor) return Boolean;
  73    --  Equivalent to Position /= No_Element
  74
  75    package Set_Iterator_Interfaces is new
  76      Ada.Iterator_Interfaces (Cursor, Has_Element);
  77
  78    function "=" (Left, Right : Set) return Boolean;
  79    --  For each element in Left, set equality attempts to find the equal
  80    --  element in Right; if a search fails, then set equality immediately
  81    --  returns False. The search works by calling Hash to find the bucket in
  82    --  the Right set that corresponds to the Left element. If the bucket is
  83    --  non-empty, the search calls the generic formal element equality operator
  84    --  to compare the element (in Left) to the element of each node in the
  85    --  bucket (in Right); the search terminates when a matching node in the
  86    --  bucket is found, or the nodes in the bucket are exhausted. (Note that
  87    --  element equality is called here, not Equivalent_Elements. Set equality
  88    --  is the only operation in which element equality is used. Compare set
  89    --  equality to Equivalent_Sets, which does call Equivalent_Elements.)
  90
  91    function Equivalent_Sets (Left, Right : Set) return Boolean;
  92    --  Similar to set equality, with the difference that the element in Left is
  93    --  compared to the elements in Right using the generic formal
  94    --  Equivalent_Elements operation instead of element equality.
  95
  96    function To_Set (New_Item : Element_Type) return Set;
  97    --  Constructs a singleton set comprising New_Element. To_Set calls Hash to
  98    --  determine the bucket for New_Item.
  99
 100    function Capacity (Container : Set) return Count_Type;
 101    --  Returns the current capacity of the set. Capacity is the maximum length
 102    --  before which rehashing in guaranteed not to occur.
 103
 104    procedure Reserve_Capacity (Container : in out Set; Capacity : Count_Type);
 105    --  If the value of the Capacity actual parameter is less or equal to
 106    --  Container.Capacity, then the operation has no effect.  Otherwise it
 107    --  raises Capacity_Error (as no expansion of capacity is possible for a
 108    --  bounded form).
 109
 110    function Default_Modulus (Capacity : Count_Type) return Hash_Type;
 111    --  Returns a modulus value (hash table size) which is optimal for the
 112    --  specified capacity (which corresponds to the maximum number of items).
 113
 114    function Length (Container : Set) return Count_Type;
 115    --  Returns the number of items in the set
 116
 117    function Is_Empty (Container : Set) return Boolean;
 118    --  Equivalent to Length (Container) = 0
 119
 120    procedure Clear (Container : in out Set);
 121    --  Removes all of the items from the set
 122
 123    function Element (Position : Cursor) return Element_Type;
 124    --  Returns the element of the node designated by the cursor
 125
 126    procedure Replace_Element
 127      (Container : in out Set;
 128       Position  : Cursor;
 129       New_Item  : Element_Type);
 130    --  If New_Item is equivalent (as determined by calling Equivalent_Elements)
 131    --  to the element of the node designated by Position, then New_Element is
 132    --  assigned to that element. Otherwise, it calls Hash to determine the
 133    --  bucket for New_Item. If the bucket is not empty, then it calls
 134    --  Equivalent_Elements for each node in that bucket to determine whether
 135    --  New_Item is equivalent to an element in that bucket. If
 136    --  Equivalent_Elements returns True then Program_Error is raised (because
 137    --  an element may appear only once in the set); otherwise, New_Item is
 138    --  assigned to the node designated by Position, and the node is moved to
 139    --  its new bucket.
 140
 141    procedure Query_Element
 142      (Position : Cursor;
 143       Process  : not null access procedure (Element : Element_Type));
 144    --  Calls Process with the element (having only a constant view) of the node
 145    --  designated by the cursor.
 146
 147    type Constant_Reference_Type
 148      (Element : not null access constant Element_Type) is private
 149         with Implicit_Dereference => Element;
 150
 151    function Constant_Reference
 152      (Container : aliased Set;
 153       Position  : Cursor) return Constant_Reference_Type;
 154
 155    procedure Assign (Target : in out Set; Source : Set);
 156    --  If Target denotes the same object as Source, then the operation has no
 157    --  effect. If the Target capacity is less than the Source length, then
 158    --  Assign raises Capacity_Error.  Otherwise, Assign clears Target and then
 159    --  copies the (active) elements from Source to Target.
 160
 161    function Copy
 162      (Source   : Set;
 163       Capacity : Count_Type := 0;
 164       Modulus  : Hash_Type := 0) return Set;
 165    --  Constructs a new set object whose elements correspond to Source.  If the
 166    --  Capacity parameter is 0, then the capacity of the result is the same as
 167    --  the length of Source. If the Capacity parameter is equal or greater than
 168    --  the length of Source, then the capacity of the result is the specified
 169    --  value. Otherwise, Copy raises Capacity_Error. If the Modulus parameter
 170    --  is 0, then the modulus of the result is the value returned by a call to
 171    --  Default_Modulus with the capacity parameter determined as above;
 172    --  otherwise the modulus of the result is the specified value.
 173
 174    procedure Move (Target : in out Set; Source : in out Set);
 175    --  Clears Target (if it's not empty), and then moves (not copies) the
 176    --  buckets array and nodes from Source to Target.
 177
 178    procedure Insert
 179      (Container : in out Set;
 180       New_Item  : Element_Type;
 181       Position  : out Cursor;
 182       Inserted  : out Boolean);
 183    --  Conditionally inserts New_Item into the set. If New_Item is already in
 184    --  the set, then Inserted returns False and Position designates the node
 185    --  containing the existing element (which is not modified). If New_Item is
 186    --  not already in the set, then Inserted returns True and Position
 187    --  designates the newly-inserted node containing New_Item. The search for
 188    --  an existing element works as follows. Hash is called to determine
 189    --  New_Item's bucket; if the bucket is non-empty, then Equivalent_Elements
 190    --  is called to compare New_Item to the element of each node in that
 191    --  bucket. If the bucket is empty, or there were no equivalent elements in
 192    --  the bucket, the search "fails" and the New_Item is inserted in the set
 193    --  (and Inserted returns True); otherwise, the search "succeeds" (and
 194    --  Inserted returns False).
 195
 196    procedure Insert  (Container : in out Set; New_Item : Element_Type);
 197    --  Attempts to insert New_Item into the set, performing the usual insertion
 198    --  search (which involves calling both Hash and Equivalent_Elements); if
 199    --  the search succeeds (New_Item is equivalent to an element already in the
 200    --  set, and so was not inserted), then this operation raises
 201    --  Constraint_Error. (This version of Insert is similar to Replace, but
 202    --  having the opposite exception behavior. It is intended for use when you
 203    --  want to assert that the item is not already in the set.)
 204
 205    procedure Include (Container : in out Set; New_Item : Element_Type);
 206    --  Attempts to insert New_Item into the set. If an element equivalent to
 207    --  New_Item is already in the set (the insertion search succeeded, and
 208    --  hence New_Item was not inserted), then the value of New_Item is assigned
 209    --  to the existing element. (This insertion operation only raises an
 210    --  exception if cursor tampering occurs. It is intended for use when you
 211    --  want to insert the item in the set, and you don't care whether an
 212    --  equivalent element is already present.)
 213
 214    procedure Replace (Container : in out Set; New_Item : Element_Type);
 215    --  Searches for New_Item in the set; if the search fails (because an
 216    --  equivalent element was not in the set), then it raises
 217    --  Constraint_Error. Otherwise, the existing element is assigned the value
 218    --  New_Item. (This is similar to Insert, but with the opposite exception
 219    --  behavior. It is intended for use when you want to assert that the item
 220    --  is already in the set.)
 221
 222    procedure Exclude (Container : in out Set; Item : Element_Type);
 223    --  Searches for Item in the set, and if found, removes its node from the
 224    --  set and then deallocates it. The search works as follows. The operation
 225    --  calls Hash to determine the item's bucket; if the bucket is not empty,
 226    --  it calls Equivalent_Elements to compare Item to the element of each node
 227    --  in the bucket. (This is the deletion analog of Include. It is intended
 228    --  for use when you want to remove the item from the set, but don't care
 229    --  whether the item is already in the set.)
 230
 231    procedure Delete  (Container : in out Set; Item : Element_Type);
 232    --  Searches for Item in the set (which involves calling both Hash and
 233    --  Equivalent_Elements). If the search fails, then the operation raises
 234    --  Constraint_Error. Otherwise it removes the node from the set and then
 235    --  deallocates it. (This is the deletion analog of non-conditional
 236    --  Insert. It is intended for use when you want to assert that the item is
 237    --  already in the set.)
 238
 239    procedure Delete (Container : in out Set; Position : in out Cursor);
 240    --  Removes the node designated by Position from the set, and then
 241    --  deallocates the node. The operation calls Hash to determine the bucket,
 242    --  and then compares Position to each node in the bucket until there's a
 243    --  match (it does not call Equivalent_Elements).
 244
 245    procedure Union (Target : in out Set; Source : Set);
 246    --  Iterates over the Source set, and conditionally inserts each element
 247    --  into Target.
 248
 249    function Union (Left, Right : Set) return Set;
 250    --  The operation first copies the Left set to the result, and then iterates
 251    --  over the Right set to conditionally insert each element into the result.
 252
 253    function "or" (Left, Right : Set) return Set renames Union;
 254
 255    procedure Intersection (Target : in out Set; Source : Set);
 256    --  Iterates over the Target set (calling First and Next), calling Find to
 257    --  determine whether the element is in Source. If an equivalent element is
 258    --  not found in Source, the element is deleted from Target.
 259
 260    function Intersection (Left, Right : Set) return Set;
 261    --  Iterates over the Left set, calling Find to determine whether the
 262    --  element is in Right. If an equivalent element is found, it is inserted
 263    --  into the result set.
 264
 265    function "and" (Left, Right : Set) return Set renames Intersection;
 266
 267    procedure Difference (Target : in out Set; Source : Set);
 268    --  Iterates over the Source (calling First and Next), calling Find to
 269    --  determine whether the element is in Target. If an equivalent element is
 270    --  found, it is deleted from Target.
 271
 272    function Difference (Left, Right : Set) return Set;
 273    --  Iterates over the Left set, calling Find to determine whether the
 274    --  element is in the Right set. If an equivalent element is not found, the
 275    --  element is inserted into the result set.
 276
 277    function "-" (Left, Right : Set) return Set renames Difference;
 278
 279    procedure Symmetric_Difference (Target : in out Set; Source : Set);
 280    --  The operation iterates over the Source set, searching for the element
 281    --  in Target (calling Hash and Equivalent_Elements). If an equivalent
 282    --  element is found, it is removed from Target; otherwise it is inserted
 283    --  into Target.
 284
 285    function Symmetric_Difference (Left, Right : Set) return Set;
 286    --  The operation first iterates over the Left set. It calls Find to
 287    --  determine whether the element is in the Right set. If no equivalent
 288    --  element is found, the element from Left is inserted into the result. The
 289    --  operation then iterates over the Right set, to determine whether the
 290    --  element is in the Left set. If no equivalent element is found, the Right
 291    --  element is inserted into the result.
 292
 293    function "xor" (Left, Right : Set) return Set
 294      renames Symmetric_Difference;
 295
 296    function Overlap (Left, Right : Set) return Boolean;
 297    --  Iterates over the Left set (calling First and Next), calling Find to
 298    --  determine whether the element is in the Right set. If an equivalent
 299    --  element is found, the operation immediately returns True. The operation
 300    --  returns False if the iteration over Left terminates without finding any
 301    --  equivalent element in Right.
 302
 303    function Is_Subset (Subset : Set; Of_Set : Set) return Boolean;
 304    --  Iterates over Subset (calling First and Next), calling Find to determine
 305    --  whether the element is in Of_Set. If no equivalent element is found in
 306    --  Of_Set, the operation immediately returns False. The operation returns
 307    --  True if the iteration over Subset terminates without finding an element
 308    --  not in Of_Set (that is, every element in Subset is equivalent to an
 309    --  element in Of_Set).
 310
 311    function First (Container : Set) return Cursor;
 312    --  Returns a cursor that designates the first non-empty bucket, by
 313    --  searching from the beginning of the buckets array.
 314
 315    function Next (Position : Cursor) return Cursor;
 316    --  Returns a cursor that designates the node that follows the current one
 317    --  designated by Position. If Position designates the last node in its
 318    --  bucket, the operation calls Hash to compute the index of this bucket,
 319    --  and searches the buckets array for the first non-empty bucket, starting
 320    --  from that index; otherwise, it simply follows the link to the next node
 321    --  in the same bucket.
 322
 323    procedure Next (Position : in out Cursor);
 324    --  Equivalent to Position := Next (Position)
 325
 326    function Find
 327      (Container : Set;
 328       Item      : Element_Type) return Cursor;
 329    --  Searches for Item in the set. Find calls Hash to determine the item's
 330    --  bucket; if the bucket is not empty, it calls Equivalent_Elements to
 331    --  compare Item to each element in the bucket. If the search succeeds, Find
 332    --  returns a cursor designating the node containing the equivalent element;
 333    --  otherwise, it returns No_Element.
 334
 335    function Contains (Container : Set; Item : Element_Type) return Boolean;
 336    --  Equivalent to Find (Container, Item) /= No_Element
 337
 338    function Equivalent_Elements (Left, Right : Cursor) return Boolean;
 339    --  Returns the result of calling Equivalent_Elements with the elements of
 340    --  the nodes designated by cursors Left and Right.
 341
 342    function Equivalent_Elements
 343      (Left  : Cursor;
 344       Right : Element_Type) return Boolean;
 345    --  Returns the result of calling Equivalent_Elements with element of the
 346    --  node designated by Left and element Right.
 347
 348    function Equivalent_Elements
 349      (Left  : Element_Type;
 350       Right : Cursor) return Boolean;
 351    --  Returns the result of calling Equivalent_Elements with element Left and
 352    --  the element of the node designated by Right.
 353
 354    procedure Iterate
 355      (Container : Set;
 356       Process   : not null access procedure (Position : Cursor));
 357    --  Calls Process for each node in the set
 358
 359    function Iterate
 360      (Container : Set)
 361       return Set_Iterator_Interfaces.Forward_Iterator'Class;
 362
 363    generic
 364       type Key_Type (<>) is private;
 365
 366       with function Key (Element : Element_Type) return Key_Type;
 367
 368       with function Hash (Key : Key_Type) return Hash_Type;
 369
 370       with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
 371
 372    package Generic_Keys is
 373
 374       function Key (Position : Cursor) return Key_Type;
 375       --  Applies generic formal operation Key to the element of the node
 376       --  designated by Position.
 377
 378       function Element (Container : Set; Key : Key_Type) return Element_Type;
 379       --  Searches (as per the key-based Find) for the node containing Key, and
 380       --  returns the associated element.
 381
 382       procedure Replace
 383         (Container : in out Set;
 384          Key       : Key_Type;
 385          New_Item  : Element_Type);
 386       --  Searches (as per the key-based Find) for the node containing Key, and
 387       --  then replaces the element of that node (as per the element-based
 388       --  Replace_Element).
 389
 390       procedure Exclude (Container : in out Set; Key : Key_Type);
 391       --  Searches for Key in the set, and if found, removes its node from the
 392       --  set and then deallocates it. The search works by first calling Hash
 393       --  (on Key) to determine the bucket; if the bucket is not empty, it
 394       --  calls Equivalent_Keys to compare parameter Key to the value of
 395       --  generic formal operation Key applied to element of each node in the
 396       --  bucket.
 397
 398       procedure Delete (Container : in out Set; Key : Key_Type);
 399       --  Deletes the node containing Key as per Exclude, with the difference
 400       --  that Constraint_Error is raised if Key is not found.
 401
 402       function Find (Container : Set; Key : Key_Type) return Cursor;
 403       --  Searches for the node containing Key, and returns a cursor
 404       --  designating the node. The search works by first calling Hash (on Key)
 405       --  to determine the bucket. If the bucket is not empty, the search
 406       --  compares Key to the element of each node in the bucket, and returns
 407       --  the matching node. The comparison itself works by applying the
 408       --  generic formal Key operation to the element of the node, and then
 409       --  calling generic formal operation Equivalent_Keys.
 410
 411       function Contains (Container : Set; Key : Key_Type) return Boolean;
 412       --  Equivalent to Find (Container, Key) /= No_Element
 413
 414       procedure Update_Element_Preserving_Key
 415         (Container : in out Set;
 416          Position  : Cursor;
 417          Process   : not null access
 418                        procedure (Element : in out Element_Type));
 419       --  Calls Process with the element of the node designated by Position,
 420       --  but with the restriction that the key-value of the element is not
 421       --  modified. The operation first makes a copy of the value returned by
 422       --  applying generic formal operation Key on the element of the node, and
 423       --  then calls Process with the element. The operation verifies that the
 424       --  key-part has not been modified by calling generic formal operation
 425       --  Equivalent_Keys to compare the saved key-value to the value returned
 426       --  by applying generic formal operation Key to the post-Process value of
 427       --  element. If the key values compare equal then the operation
 428       --  completes. Otherwise, the node is removed from the map and
 429       --  Program_Error is raised.
 430
 431       type Reference_Type (Element : not null access Element_Type) is private
 432         with Implicit_Dereference => Element;
 433
 434       function Reference_Preserving_Key
 435         (Container : aliased in out Set;
 436          Position  : Cursor) return Reference_Type;
 437
 438       function Constant_Reference
 439         (Container : aliased Set;
 440          Key       : Key_Type) return Constant_Reference_Type;
 441
 442       function Reference_Preserving_Key
 443         (Container : aliased in out Set;
 444          Key       : Key_Type) return Reference_Type;
 445
 446    private
 447       type Reference_Type (Element : not null access Element_Type)
 448          is null record;
 449
 450       use Ada.Streams;
 451
 452       procedure Read
 453         (Stream : not null access Root_Stream_Type'Class;
 454          Item   : out Reference_Type);
 455
 456       for Reference_Type'Read use Read;
 457
 458       procedure Write
 459         (Stream : not null access Root_Stream_Type'Class;
 460          Item   : Reference_Type);
 461
 462       for Reference_Type'Write use Write;
 463
 464    end Generic_Keys;
 465
 466 private
 467    pragma Inline (Next);
 468
 469    type Node_Type is record
 470       Element : aliased Element_Type;
 471       Next    : Count_Type;
 472    end record;
 473
 474    package HT_Types is
 475      new Hash_Tables.Generic_Bounded_Hash_Table_Types (Node_Type);
 476
 477    type Set (Capacity : Count_Type; Modulus : Hash_Type) is
 478       new HT_Types.Hash_Table_Type (Capacity, Modulus) with null record;
 479
 480    use HT_Types;
 481    use Ada.Streams;
 482
 483    procedure Write
 484      (Stream    : not null access Root_Stream_Type'Class;
 485       Container : Set);
 486
 487    for Set'Write use Write;
 488
 489    procedure Read
 490      (Stream    : not null access Root_Stream_Type'Class;
 491       Container : out Set);
 492
 493    for Set'Read use Read;
 494
 495    type Set_Access is access all Set;
 496    for Set_Access'Storage_Size use 0;
 497
 498    --  Note: If a Cursor object has no explicit initialization expression,
 499    --  it must default initialize to the same value as constant No_Element.
 500    --  The Node component of type Cursor has scalar type Count_Type, so it
 501    --  requires an explicit initialization expression of its own declaration,
 502    --  in order for objects of record type Cursor to properly initialize.
 503
 504    type Cursor is record
 505       Container : Set_Access;
 506       Node      : Count_Type := 0;
 507    end record;
 508
 509    procedure Write
 510      (Stream : not null access Root_Stream_Type'Class;
 511       Item   : Cursor);
 512
 513    for Cursor'Write use Write;
 514
 515    procedure Read
 516      (Stream : not null access Root_Stream_Type'Class;
 517       Item   : out Cursor);
 518
 519    for Cursor'Read use Read;
 520
 521    type Constant_Reference_Type
 522      (Element : not null access constant Element_Type) is null record;
 523
 524    procedure Read
 525      (Stream : not null access Root_Stream_Type'Class;
 526       Item   : out Constant_Reference_Type);
 527
 528    for Constant_Reference_Type'Read use Read;
 529
 530    procedure Write
 531      (Stream : not null access Root_Stream_Type'Class;
 532       Item   : Constant_Reference_Type);
 533
 534    for Constant_Reference_Type'Write use Write;
 535
 536    Empty_Set : constant Set :=
 537                  (Hash_Table_Type with Capacity => 0, Modulus => 0);
 538
 539    No_Element : constant Cursor := (Container => null, Node => 0);
 540
 541    type Iterator is new Limited_Controlled and
 542      Set_Iterator_Interfaces.Forward_Iterator with
 543    record
 544       Container : Set_Access;
 545    end record;
 546
 547    overriding procedure Finalize (Object : in out Iterator);
 548
 549    overriding function First (Object : Iterator) return Cursor;
 550
 551    overriding function Next
 552      (Object   : Iterator;
 553       Position : Cursor) return Cursor;
 554
 555 end Ada.Containers.Bounded_Hashed_Sets;