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------------------------------------------------------------------------------
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--                         GNAT LIBRARY COMPONENTS                          --
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--    A D A . C O N T A I N E R S . F O R M A L _ H A S H E D _ M A P S     --
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------------------------------------------------------------------------------

--  This spec is derived from package Ada.Containers.Bounded_Hashed_Maps in the
--  Ada 2012 RM. The modifications are meant to facilitate formal proofs by
--  making it easier to express properties, and by making the specification of
--  this unit compatible with SPARK 2014. Note that the API of this unit may be
--  subject to incompatible changes as SPARK 2014 evolves.

--  The modifications are:

--    A parameter for the container is added to every function reading the
--    contents of a container: Key, Element, Next, Query_Element, Has_Element,
--    Iterate, Equivalent_Keys. This change is motivated by the need to have
--    cursors which are valid on different containers (typically a container C
--    and its previous version C'Old) for expressing properties, which is not
--    possible if cursors encapsulate an access to the underlying container.

--    There are four new functions:

--      function Strict_Equal (Left, Right : Map) return Boolean;
--      function Overlap (Left, Right : Map) return Boolean;
--      function First_To_Previous (Container : Map; Current : Cursor)
--         return Map;
--      function Current_To_Last (Container : Map; Current : Cursor)
--         return Map;

--    See detailed specifications for these subprograms

private with Ada.Containers.Hash_Tables;

generic
   type Key_Type is private;
   type Element_Type is private;

   with function Hash (Key : Key_Type) return Hash_Type;
   with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
   with function "=" (Left, Right : Element_Type) return Boolean is <>;

package Ada.Containers.Formal_Hashed_Maps is
   pragma Annotate (GNATprove, External_Axiomatization);
   pragma Pure;

   type Map (Capacity : Count_Type; Modulus : Hash_Type) is private with
     Iterable => (First       => First,
                  Next        => Next,
                  Has_Element => Has_Element,
                  Element     => Element);
   pragma Preelaborable_Initialization (Map);

   type Cursor is private;
   pragma Preelaborable_Initialization (Cursor);

   Empty_Map : constant Map;

   No_Element : constant Cursor;

   function "=" (Left, Right : Map) return Boolean with
     Global => null;

   function Capacity (Container : Map) return Count_Type with
     Global => null;

   procedure Reserve_Capacity
     (Container : in out Map;
      Capacity  : Count_Type)
   with
     Global => null,
     Pre    => Capacity <= Container.Capacity;

   function Length (Container : Map) return Count_Type with
     Global => null;

   function Is_Empty (Container : Map) return Boolean with
     Global => null;

   procedure Clear (Container : in out Map) with
     Global => null;

   procedure Assign (Target : in out Map; Source : Map) with
     Global => null,
     Pre    => Target.Capacity >= Length (Source);

   function Copy
     (Source   : Map;
      Capacity : Count_Type := 0) return Map
   with
     Global => null,
     Pre    => Capacity = 0 or else Capacity >= Source.Capacity;
   --  Copy returns a container stricty equal to Source. It must have
   --  the same cursors associated with each element. Therefore:
   --  - capacity=0 means use container.capacity as capacity of target
   --  - the modulus cannot be changed.

   function Key (Container : Map; Position : Cursor) return Key_Type with
     Global => null,
     Pre    => Has_Element (Container, Position);

   function Element
     (Container : Map;
      Position  : Cursor) return Element_Type
   with
     Global => null,
     Pre    => Has_Element (Container, Position);

   procedure Replace_Element
     (Container : in out Map;
      Position  : Cursor;
      New_Item  : Element_Type)
   with
     Global => null,
     Pre    => Has_Element (Container, Position);

   procedure Move (Target : in out Map; Source : in out Map) with
     Global => null,
     Pre    => Target.Capacity >= Length (Source);

   procedure Insert
     (Container : in out Map;
      Key       : Key_Type;
      New_Item  : Element_Type;
      Position  : out Cursor;
      Inserted  : out Boolean)
   with
     Global => null,
     Pre    => Length (Container) < Container.Capacity;

   procedure Insert
     (Container : in out Map;
      Key       : Key_Type;
      New_Item  : Element_Type)
   with
     Global => null,
     Pre    => Length (Container) < Container.Capacity
                 and then (not Contains (Container, Key));

   procedure Include
     (Container : in out Map;
      Key       : Key_Type;
      New_Item  : Element_Type)
   with
     Global => null,
     Pre    => Length (Container) < Container.Capacity;

   procedure Replace
     (Container : in out Map;
      Key       : Key_Type;
      New_Item  : Element_Type)
   with
     Global => null,
     Pre    => Contains (Container, Key);

   procedure Exclude (Container : in out Map; Key : Key_Type) with
     Global => null;

   procedure Delete (Container : in out Map; Key : Key_Type) with
     Global => null,
     Pre    => Contains (Container, Key);

   procedure Delete (Container : in out Map; Position : in out Cursor) with
     Global => null,
     Pre    => Has_Element (Container, Position);

   function First (Container : Map) return Cursor with
     Global => null;

   function Next (Container : Map; Position : Cursor) return Cursor with
     Global => null,
     Pre    => Has_Element (Container, Position) or else Position = No_Element;

   procedure Next (Container : Map; Position : in out Cursor) with
     Global => null,
     Pre    => Has_Element (Container, Position) or else Position = No_Element;

   function Find (Container : Map; Key : Key_Type) return Cursor with
     Global => null;

   function Contains (Container : Map; Key : Key_Type) return Boolean with
     Global => null;

   function Element (Container : Map; Key : Key_Type) return Element_Type with
     Global => null,
     Pre    => Contains (Container, Key);

   function Has_Element (Container : Map; Position : Cursor) return Boolean
   with
     Global => null;

   function Equivalent_Keys
     (Left   : Map;
      CLeft  : Cursor;
      Right  : Map;
      CRight : Cursor) return Boolean
   with
     Global => null;

   function Equivalent_Keys
     (Left  : Map;
      CLeft : Cursor;
      Right : Key_Type) return Boolean
   with
     Global => null;

   function Equivalent_Keys
     (Left   : Key_Type;
      Right  : Map;
      CRight : Cursor) return Boolean
   with
     Global => null;

   function Default_Modulus (Capacity : Count_Type) return Hash_Type with
     Global => null;

   function Strict_Equal (Left, Right : Map) return Boolean with
     Global => null;
   --  Strict_Equal returns True if the containers are physically equal, i.e.
   --  they are structurally equal (function "=" returns True) and that they
   --  have the same set of cursors.

   function First_To_Previous (Container : Map; Current : Cursor) return Map
   with
     Global => null,
     Pre    => Has_Element (Container, Current) or else Current = No_Element;
   function Current_To_Last (Container : Map; Current : Cursor) return Map
   with
     Global => null,
     Pre    => Has_Element (Container, Current) or else Current = No_Element;
   --  First_To_Previous returns a container containing all elements preceding
   --  Current (excluded) in Container. Current_To_Last returns a container
   --  containing all elements following Current (included) in Container.
   --  These two new functions can be used to express invariant properties in
   --  loops which iterate over containers. First_To_Previous returns the part
   --  of the container already scanned and Current_To_Last the part not
   --  scanned yet.

   function Overlap (Left, Right : Map) return Boolean with
     Global => null;
   --  Overlap returns True if the containers have common keys

private
   pragma Inline (Length);
   pragma Inline (Is_Empty);
   pragma Inline (Clear);
   pragma Inline (Key);
   pragma Inline (Element);
   pragma Inline (Contains);
   pragma Inline (Capacity);
   pragma Inline (Has_Element);
   pragma Inline (Equivalent_Keys);
   pragma Inline (Next);

   type Node_Type is record
      Key         : Key_Type;
      Element     : Element_Type;
      Next        : Count_Type;
      Has_Element : Boolean := False;
   end record;

   package HT_Types is new
     Ada.Containers.Hash_Tables.Generic_Bounded_Hash_Table_Types
       (Node_Type);

   type Map (Capacity : Count_Type; Modulus : Hash_Type) is
      new HT_Types.Hash_Table_Type (Capacity, Modulus) with null record;

   use HT_Types;

   type Cursor is record
      Node : Count_Type;
   end record;

   Empty_Map : constant Map := (Capacity => 0, Modulus => 0, others => <>);

   No_Element : constant Cursor := (Node => 0);

end Ada.Containers.Formal_Hashed_Maps;