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------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- A D A . C O N T A I N E R S . H A S H E D _ S E T S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2004-2021, Free Software Foundation, Inc. --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
-- apply solely to the contents of the part following the private keyword. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- This unit was originally developed by Matthew J Heaney. --
------------------------------------------------------------------------------
with Ada.Iterator_Interfaces;
private with Ada.Containers.Hash_Tables;
with Ada.Containers.Helpers;
private with Ada.Finalization;
private with Ada.Streams;
private with Ada.Strings.Text_Buffers;
generic
type Element_Type is private;
with function Hash (Element : Element_Type) return Hash_Type;
with function Equivalent_Elements
(Left, Right : Element_Type) return Boolean;
with function "=" (Left, Right : Element_Type) return Boolean is <>;
package Ada.Containers.Hashed_Sets with
SPARK_Mode => Off
is
pragma Annotate (CodePeer, Skip_Analysis);
pragma Preelaborate;
pragma Remote_Types;
type Set is tagged private
with
Constant_Indexing => Constant_Reference,
Default_Iterator => Iterate,
Iterator_Element => Element_Type,
Aggregate => (Empty => Empty,
Add_Unnamed => Include);
pragma Preelaborable_Initialization (Set);
type Cursor is private;
pragma Preelaborable_Initialization (Cursor);
function "=" (Left, Right : Cursor) return Boolean;
-- The representation of cursors includes a component used to optimize
-- iteration over sets. This component may become unreliable after
-- multiple set insertions, and must be excluded from cursor equality,
-- so we need to provide an explicit definition for it, instead of
-- using predefined equality (as implied by a questionable comment
-- in the RM). This is also the case for hashed maps, and affects the
-- use of Insert primitives in hashed structures.
Empty_Set : constant Set;
-- Set objects declared without an initialization expression are
-- initialized to the value Empty_Set.
No_Element : constant Cursor;
-- Cursor objects declared without an initialization expression are
-- initialized to the value No_Element.
function Has_Element (Position : Cursor) return Boolean;
-- Equivalent to Position /= No_Element
package Set_Iterator_Interfaces is new
Ada.Iterator_Interfaces (Cursor, Has_Element);
function Empty (Capacity : Count_Type := 1000) return Set;
function "=" (Left, Right : Set) return Boolean;
-- For each element in Left, set equality attempts to find the equal
-- element in Right; if a search fails, then set equality immediately
-- returns False. The search works by calling Hash to find the bucket in
-- the Right set that corresponds to the Left element. If the bucket is
-- non-empty, the search calls the generic formal element equality operator
-- to compare the element (in Left) to the element of each node in the
-- bucket (in Right); the search terminates when a matching node in the
-- bucket is found, or the nodes in the bucket are exhausted. (Note that
-- element equality is called here, not Equivalent_Elements. Set equality
-- is the only operation in which element equality is used. Compare set
-- equality to Equivalent_Sets, which does call Equivalent_Elements.)
function Equivalent_Sets (Left, Right : Set) return Boolean;
-- Similar to set equality, with the difference that the element in Left is
-- compared to the elements in Right using the generic formal
-- Equivalent_Elements operation instead of element equality.
function To_Set (New_Item : Element_Type) return Set;
-- Constructs a singleton set comprising New_Element. To_Set calls Hash to
-- determine the bucket for New_Item.
function Capacity (Container : Set) return Count_Type;
-- Returns the current capacity of the set. Capacity is the maximum length
-- before which rehashing in guaranteed not to occur.
procedure Reserve_Capacity (Container : in out Set; Capacity : Count_Type);
-- Adjusts the current capacity, by allocating a new buckets array. If the
-- requested capacity is less than the current capacity, then the capacity
-- is contracted (to a value not less than the current length). If the
-- requested capacity is greater than the current capacity, then the
-- capacity is expanded (to a value not less than what is requested). In
-- either case, the nodes are rehashed from the old buckets array onto the
-- new buckets array (Hash is called once for each existing element in
-- order to compute the new index), and then the old buckets array is
-- deallocated.
function Length (Container : Set) return Count_Type;
-- Returns the number of items in the set
function Is_Empty (Container : Set) return Boolean;
-- Equivalent to Length (Container) = 0
procedure Clear (Container : in out Set);
-- Removes all of the items from the set
function Element (Position : Cursor) return Element_Type;
-- Returns the element of the node designated by the cursor
procedure Replace_Element
(Container : in out Set;
Position : Cursor;
New_Item : Element_Type);
-- If New_Item is equivalent (as determined by calling Equivalent_Elements)
-- to the element of the node designated by Position, then New_Element is
-- assigned to that element. Otherwise, it calls Hash to determine the
-- bucket for New_Item. If the bucket is not empty, then it calls
-- Equivalent_Elements for each node in that bucket to determine whether
-- New_Item is equivalent to an element in that bucket. If
-- Equivalent_Elements returns True then Program_Error is raised (because
-- an element may appear only once in the set); otherwise, New_Item is
-- assigned to the node designated by Position, and the node is moved to
-- its new bucket.
procedure Query_Element
(Position : Cursor;
Process : not null access procedure (Element : Element_Type));
-- Calls Process with the element (having only a constant view) of the node
-- designed by the cursor.
type Constant_Reference_Type
(Element : not null access constant Element_Type) is private
with Implicit_Dereference => Element;
function Constant_Reference
(Container : aliased Set;
Position : Cursor) return Constant_Reference_Type;
pragma Inline (Constant_Reference);
procedure Assign (Target : in out Set; Source : Set);
function Copy (Source : Set; Capacity : Count_Type := 0) return Set;
procedure Move (Target : in out Set; Source : in out Set);
-- Clears Target (if it's not empty), and then moves (not copies) the
-- buckets array and nodes from Source to Target.
procedure Insert
(Container : in out Set;
New_Item : Element_Type;
Position : out Cursor;
Inserted : out Boolean);
-- Conditionally inserts New_Item into the set. If New_Item is already in
-- the set, then Inserted returns False and Position designates the node
-- containing the existing element (which is not modified). If New_Item is
-- not already in the set, then Inserted returns True and Position
-- designates the newly-inserted node containing New_Item. The search for
-- an existing element works as follows. Hash is called to determine
-- New_Item's bucket; if the bucket is non-empty, then Equivalent_Elements
-- is called to compare New_Item to the element of each node in that
-- bucket. If the bucket is empty, or there were no equivalent elements in
-- the bucket, the search "fails" and the New_Item is inserted in the set
-- (and Inserted returns True); otherwise, the search "succeeds" (and
-- Inserted returns False).
procedure Insert (Container : in out Set; New_Item : Element_Type);
-- Attempts to insert New_Item into the set, performing the usual insertion
-- search (which involves calling both Hash and Equivalent_Elements); if
-- the search succeeds (New_Item is equivalent to an element already in the
-- set, and so was not inserted), then this operation raises
-- Constraint_Error. (This version of Insert is similar to Replace, but
-- having the opposite exception behavior. It is intended for use when you
-- want to assert that the item is not already in the set.)
procedure Include (Container : in out Set; New_Item : Element_Type);
-- Attempts to insert New_Item into the set. If an element equivalent to
-- New_Item is already in the set (the insertion search succeeded, and
-- hence New_Item was not inserted), then the value of New_Item is assigned
-- to the existing element. (This insertion operation only raises an
-- exception if cursor tampering occurs. It is intended for use when you
-- want to insert the item in the set, and you don't care whether an
-- equivalent element is already present.)
procedure Replace (Container : in out Set; New_Item : Element_Type);
-- Searches for New_Item in the set; if the search fails (because an
-- equivalent element was not in the set), then it raises
-- Constraint_Error. Otherwise, the existing element is assigned the value
-- New_Item. (This is similar to Insert, but with the opposite exception
-- behavior. It is intended for use when you want to assert that the item
-- is already in the set.)
procedure Exclude (Container : in out Set; Item : Element_Type);
-- Searches for Item in the set, and if found, removes its node from the
-- set and then deallocates it. The search works as follows. The operation
-- calls Hash to determine the item's bucket; if the bucket is not empty,
-- it calls Equivalent_Elements to compare Item to the element of each node
-- in the bucket. (This is the deletion analog of Include. It is intended
-- for use when you want to remove the item from the set, but don't care
-- whether the item is already in the set.)
procedure Delete (Container : in out Set; Item : Element_Type);
-- Searches for Item in the set (which involves calling both Hash and
-- Equivalent_Elements). If the search fails, then the operation raises
-- Constraint_Error. Otherwise it removes the node from the set and then
-- deallocates it. (This is the deletion analog of non-conditional
-- Insert. It is intended for use when you want to assert that the item is
-- already in the set.)
procedure Delete (Container : in out Set; Position : in out Cursor);
-- Removes the node designated by Position from the set, and then
-- deallocates the node. The operation calls Hash to determine the bucket,
-- and then compares Position to each node in the bucket until there's a
-- match (it does not call Equivalent_Elements).
procedure Union (Target : in out Set; Source : Set);
-- The operation first calls Reserve_Capacity if the current capacity is
-- less than the sum of the lengths of Source and Target. It then iterates
-- over the Source set, and conditionally inserts each element into Target.
function Union (Left, Right : Set) return Set;
-- The operation first copies the Left set to the result, and then iterates
-- over the Right set to conditionally insert each element into the result.
function "or" (Left, Right : Set) return Set renames Union;
procedure Intersection (Target : in out Set; Source : Set);
-- Iterates over the Target set (calling First and Next), calling Find to
-- determine whether the element is in Source. If an equivalent element is
-- not found in Source, the element is deleted from Target.
function Intersection (Left, Right : Set) return Set;
-- Iterates over the Left set, calling Find to determine whether the
-- element is in Right. If an equivalent element is found, it is inserted
-- into the result set.
function "and" (Left, Right : Set) return Set renames Intersection;
procedure Difference (Target : in out Set; Source : Set);
-- Iterates over the Source (calling First and Next), calling Find to
-- determine whether the element is in Target. If an equivalent element is
-- found, it is deleted from Target.
function Difference (Left, Right : Set) return Set;
-- Iterates over the Left set, calling Find to determine whether the
-- element is in the Right set. If an equivalent element is not found, the
-- element is inserted into the result set.
function "-" (Left, Right : Set) return Set renames Difference;
procedure Symmetric_Difference (Target : in out Set; Source : Set);
-- The operation first calls Reserve_Capacity if the current capacity is
-- less than the sum of the lengths of Source and Target. It then iterates
-- over the Source set, searching for the element in Target (calling Hash
-- and Equivalent_Elements). If an equivalent element is found, it is
-- removed from Target; otherwise it is inserted into Target.
function Symmetric_Difference (Left, Right : Set) return Set;
-- The operation first iterates over the Left set. It calls Find to
-- determine whether the element is in the Right set. If no equivalent
-- element is found, the element from Left is inserted into the result. The
-- operation then iterates over the Right set, to determine whether the
-- element is in the Left set. If no equivalent element is found, the Right
-- element is inserted into the result.
function "xor" (Left, Right : Set) return Set
renames Symmetric_Difference;
function Overlap (Left, Right : Set) return Boolean;
-- Iterates over the Left set (calling First and Next), calling Find to
-- determine whether the element is in the Right set. If an equivalent
-- element is found, the operation immediately returns True. The operation
-- returns False if the iteration over Left terminates without finding any
-- equivalent element in Right.
function Is_Subset (Subset : Set; Of_Set : Set) return Boolean;
-- Iterates over Subset (calling First and Next), calling Find to determine
-- whether the element is in Of_Set. If no equivalent element is found in
-- Of_Set, the operation immediately returns False. The operation returns
-- True if the iteration over Subset terminates without finding an element
-- not in Of_Set (that is, every element in Subset is equivalent to an
-- element in Of_Set).
function First (Container : Set) return Cursor;
-- Returns a cursor that designates the first non-empty bucket, by
-- searching from the beginning of the buckets array.
function Next (Position : Cursor) return Cursor;
-- Returns a cursor that designates the node that follows the current one
-- designated by Position. If Position designates the last node in its
-- bucket, the operation calls Hash to compute the index of this bucket,
-- and searches the buckets array for the first non-empty bucket, starting
-- from that index; otherwise, it simply follows the link to the next node
-- in the same bucket.
procedure Next (Position : in out Cursor);
-- Equivalent to Position := Next (Position)
function Find
(Container : Set;
Item : Element_Type) return Cursor;
-- Searches for Item in the set. Find calls Hash to determine the item's
-- bucket; if the bucket is not empty, it calls Equivalent_Elements to
-- compare Item to each element in the bucket. If the search succeeds, Find
-- returns a cursor designating the node containing the equivalent element;
-- otherwise, it returns No_Element.
function Contains (Container : Set; Item : Element_Type) return Boolean;
-- Equivalent to Find (Container, Item) /= No_Element
function Equivalent_Elements (Left, Right : Cursor) return Boolean;
-- Returns the result of calling Equivalent_Elements with the elements of
-- the nodes designated by cursors Left and Right.
function Equivalent_Elements
(Left : Cursor;
Right : Element_Type) return Boolean;
-- Returns the result of calling Equivalent_Elements with element of the
-- node designated by Left and element Right.
function Equivalent_Elements
(Left : Element_Type;
Right : Cursor) return Boolean;
-- Returns the result of calling Equivalent_Elements with element Left and
-- the element of the node designated by Right.
procedure Iterate
(Container : Set;
Process : not null access procedure (Position : Cursor));
-- Calls Process for each node in the set
function Iterate
(Container : Set) return Set_Iterator_Interfaces.Forward_Iterator'Class;
generic
type Key_Type (<>) is private;
with function Key (Element : Element_Type) return Key_Type;
with function Hash (Key : Key_Type) return Hash_Type;
with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
package Generic_Keys is
function Key (Position : Cursor) return Key_Type;
-- Applies generic formal operation Key to the element of the node
-- designated by Position.
function Element (Container : Set; Key : Key_Type) return Element_Type;
-- Searches (as per the key-based Find) for the node containing Key, and
-- returns the associated element.
procedure Replace
(Container : in out Set;
Key : Key_Type;
New_Item : Element_Type);
-- Searches (as per the key-based Find) for the node containing Key, and
-- then replaces the element of that node (as per the element-based
-- Replace_Element).
procedure Exclude (Container : in out Set; Key : Key_Type);
-- Searches for Key in the set, and if found, removes its node from the
-- set and then deallocates it. The search works by first calling Hash
-- (on Key) to determine the bucket; if the bucket is not empty, it
-- calls Equivalent_Keys to compare parameter Key to the value of
-- generic formal operation Key applied to element of each node in the
-- bucket.
procedure Delete (Container : in out Set; Key : Key_Type);
-- Deletes the node containing Key as per Exclude, with the difference
-- that Constraint_Error is raised if Key is not found.
function Find (Container : Set; Key : Key_Type) return Cursor;
-- Searches for the node containing Key, and returns a cursor
-- designating the node. The search works by first calling Hash (on Key)
-- to determine the bucket. If the bucket is not empty, the search
-- compares Key to the element of each node in the bucket, and returns
-- the matching node. The comparison itself works by applying the
-- generic formal Key operation to the element of the node, and then
-- calling generic formal operation Equivalent_Keys.
function Contains (Container : Set; Key : Key_Type) return Boolean;
-- Equivalent to Find (Container, Key) /= No_Element
procedure Update_Element_Preserving_Key
(Container : in out Set;
Position : Cursor;
Process : not null access
procedure (Element : in out Element_Type));
-- Calls Process with the element of the node designated by Position,
-- but with the restriction that the key-value of the element is not
-- modified. The operation first makes a copy of the value returned by
-- applying generic formal operation Key on the element of the node, and
-- then calls Process with the element. The operation verifies that the
-- key-part has not been modified by calling generic formal operation
-- Equivalent_Keys to compare the saved key-value to the value returned
-- by applying generic formal operation Key to the post-Process value of
-- element. If the key values compare equal then the operation
-- completes. Otherwise, the node is removed from the set and
-- Program_Error is raised.
type Reference_Type (Element : not null access Element_Type) is private
with Implicit_Dereference => Element;
function Reference_Preserving_Key
(Container : aliased in out Set;
Position : Cursor) return Reference_Type;
function Constant_Reference
(Container : aliased Set;
Key : Key_Type) return Constant_Reference_Type;
function Reference_Preserving_Key
(Container : aliased in out Set;
Key : Key_Type) return Reference_Type;
private
use Ada.Streams;
type Set_Access is access all Set;
for Set_Access'Storage_Size use 0;
-- Key_Preserving references must carry information to allow removal
-- of elements whose value may have been altered improperly, i.e. have
-- been given values incompatible with the hash-code of the previous
-- value, and are thus in the wrong bucket. (RM 18.7 (96.6/3))
-- We cannot store the key directly because it is an unconstrained type.
-- To avoid using additional dynamic allocation we store the old cursor
-- which simplifies possible removal. This is not possible for some
-- other set types.
-- The mechanism is different for Update_Element_Preserving_Key, as
-- in that case the check that buckets have not changed is performed
-- at the time of the update, not when the reference is finalized.
package Impl is new Helpers.Generic_Implementation;
type Reference_Control_Type is
new Impl.Reference_Control_Type with
record
Container : Set_Access;
Index : Hash_Type;
Old_Pos : Cursor;
Old_Hash : Hash_Type;
end record;
overriding procedure Finalize (Control : in out Reference_Control_Type);
pragma Inline (Finalize);
type Reference_Type (Element : not null access Element_Type) is record
Control : Reference_Control_Type;
end record;
procedure Read
(Stream : not null access Root_Stream_Type'Class;
Item : out Reference_Type);
for Reference_Type'Read use Read;
procedure Write
(Stream : not null access Root_Stream_Type'Class;
Item : Reference_Type);
for Reference_Type'Write use Write;
end Generic_Keys;
private
pragma Inline (Next);
type Node_Type;
type Node_Access is access Node_Type;
type Node_Type is limited record
Element : aliased Element_Type;
Next : Node_Access;
end record;
package HT_Types is
new Hash_Tables.Generic_Hash_Table_Types (Node_Type, Node_Access);
type Set is new Ada.Finalization.Controlled with record
HT : HT_Types.Hash_Table_Type;
end record with Put_Image => Put_Image;
procedure Put_Image
(S : in out Ada.Strings.Text_Buffers.Root_Buffer_Type'Class; V : Set);
overriding procedure Adjust (Container : in out Set);
overriding procedure Finalize (Container : in out Set);
use HT_Types, HT_Types.Implementation;
use Ada.Finalization;
use Ada.Streams;
procedure Write
(Stream : not null access Root_Stream_Type'Class;
Container : Set);
for Set'Write use Write;
procedure Read
(Stream : not null access Root_Stream_Type'Class;
Container : out Set);
for Set'Read use Read;
type Set_Access is access all Set;
for Set_Access'Storage_Size use 0;
type Cursor is record
Container : Set_Access;
-- Access to this cursor's container
Node : Node_Access;
-- Access to the node pointed to by this cursor
Position : Hash_Type := Hash_Type'Last;
-- Position of the node in the buckets of the container. If this is
-- equal to Hash_Type'Last, then it will not be used. Position is
-- not requried by the implementation, but improves the efficiency
-- of various operations.
--
-- However, this value must be maintained so that the predefined
-- equality operation acts as required by RM A.18.7-17/2, which
-- states: "The predefined "=" operator for type Cursor returns True
-- if both cursors are No_Element, or designate the same element
-- in the same container."
end record;
procedure Write
(Stream : not null access Root_Stream_Type'Class;
Item : Cursor);
for Cursor'Write use Write;
procedure Read
(Stream : not null access Root_Stream_Type'Class;
Item : out Cursor);
for Cursor'Read use Read;
subtype Reference_Control_Type is Implementation.Reference_Control_Type;
-- It is necessary to rename this here, so that the compiler can find it
type Constant_Reference_Type
(Element : not null access constant Element_Type) is
record
Control : Reference_Control_Type :=
raise Program_Error with "uninitialized reference";
-- The RM says, "The default initialization of an object of
-- type Constant_Reference_Type or Reference_Type propagates
-- Program_Error."
end record;
procedure Read
(Stream : not null access Root_Stream_Type'Class;
Item : out Constant_Reference_Type);
for Constant_Reference_Type'Read use Read;
procedure Write
(Stream : not null access Root_Stream_Type'Class;
Item : Constant_Reference_Type);
for Constant_Reference_Type'Write use Write;
-- Three operations are used to optimize in the expansion of "for ... of"
-- loops: the Next(Cursor) procedure in the visible part, and the following
-- Pseudo_Reference and Get_Element_Access functions. See Sem_Ch5 for
-- details.
function Pseudo_Reference
(Container : aliased Set'Class) return Reference_Control_Type;
pragma Inline (Pseudo_Reference);
-- Creates an object of type Reference_Control_Type pointing to the
-- container, and increments the Lock. Finalization of this object will
-- decrement the Lock.
type Element_Access is access all Element_Type with
Storage_Size => 0;
function Get_Element_Access
(Position : Cursor) return not null Element_Access;
-- Returns a pointer to the element designated by Position.
Empty_Set : constant Set := (Controlled with others => <>);
No_Element : constant Cursor :=
(Container => null, Node => null, Position => Hash_Type'Last);
type Iterator is new Limited_Controlled and
Set_Iterator_Interfaces.Forward_Iterator with
record
Container : Set_Access;
end record
with Disable_Controlled => not T_Check;
overriding function First (Object : Iterator) return Cursor;
overriding function Next
(Object : Iterator;
Position : Cursor) return Cursor;
overriding procedure Finalize (Object : in out Iterator);
end Ada.Containers.Hashed_Sets;