------------------------------------------------------------------------------ -- -- -- GNAT LIBRARY COMPONENTS -- -- -- -- ADA.CONTAINERS.BOUNDED_DOUBLY_LINKED_LISTS -- -- -- -- B o d y -- -- -- -- Copyright (C) 2004-2018, Free Software Foundation, Inc. -- -- -- -- 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 -- -- . -- -- -- -- This unit was originally developed by Matthew J Heaney. -- ------------------------------------------------------------------------------ with System; use type System.Address; package body Ada.Containers.Bounded_Doubly_Linked_Lists is pragma Warnings (Off, "variable ""Busy*"" is not referenced"); pragma Warnings (Off, "variable ""Lock*"" is not referenced"); -- See comment in Ada.Containers.Helpers ----------------------- -- Local Subprograms -- ----------------------- procedure Allocate (Container : in out List; New_Item : Element_Type; New_Node : out Count_Type); procedure Allocate (Container : in out List; Stream : not null access Root_Stream_Type'Class; New_Node : out Count_Type); procedure Free (Container : in out List; X : Count_Type); procedure Insert_Internal (Container : in out List; Before : Count_Type; New_Node : Count_Type); procedure Splice_Internal (Target : in out List; Before : Count_Type; Source : in out List); procedure Splice_Internal (Target : in out List; Before : Count_Type; Source : in out List; Src_Pos : Count_Type; Tgt_Pos : out Count_Type); function Vet (Position : Cursor) return Boolean; -- Checks invariants of the cursor and its designated container, as a -- simple way of detecting dangling references (see operation Free for a -- description of the detection mechanism), returning True if all checks -- pass. Invocations of Vet are used here as the argument of pragma Assert, -- so the checks are performed only when assertions are enabled. --------- -- "=" -- --------- function "=" (Left, Right : List) return Boolean is begin if Left.Length /= Right.Length then return False; end if; if Left.Length = 0 then return True; end if; declare -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. Lock_Left : With_Lock (Left.TC'Unrestricted_Access); Lock_Right : With_Lock (Right.TC'Unrestricted_Access); LN : Node_Array renames Left.Nodes; RN : Node_Array renames Right.Nodes; LI : Count_Type := Left.First; RI : Count_Type := Right.First; begin for J in 1 .. Left.Length loop if LN (LI).Element /= RN (RI).Element then return False; end if; LI := LN (LI).Next; RI := RN (RI).Next; end loop; end; return True; end "="; -------------- -- Allocate -- -------------- procedure Allocate (Container : in out List; New_Item : Element_Type; New_Node : out Count_Type) is N : Node_Array renames Container.Nodes; begin if Container.Free >= 0 then New_Node := Container.Free; -- We always perform the assignment first, before we change container -- state, in order to defend against exceptions duration assignment. N (New_Node).Element := New_Item; Container.Free := N (New_Node).Next; else -- A negative free store value means that the links of the nodes in -- the free store have not been initialized. In this case, the nodes -- are physically contiguous in the array, starting at the index that -- is the absolute value of the Container.Free, and continuing until -- the end of the array (Nodes'Last). New_Node := abs Container.Free; -- As above, we perform this assignment first, before modifying any -- container state. N (New_Node).Element := New_Item; Container.Free := Container.Free - 1; end if; end Allocate; procedure Allocate (Container : in out List; Stream : not null access Root_Stream_Type'Class; New_Node : out Count_Type) is N : Node_Array renames Container.Nodes; begin if Container.Free >= 0 then New_Node := Container.Free; -- We always perform the assignment first, before we change container -- state, in order to defend against exceptions duration assignment. Element_Type'Read (Stream, N (New_Node).Element); Container.Free := N (New_Node).Next; else -- A negative free store value means that the links of the nodes in -- the free store have not been initialized. In this case, the nodes -- are physically contiguous in the array, starting at the index that -- is the absolute value of the Container.Free, and continuing until -- the end of the array (Nodes'Last). New_Node := abs Container.Free; -- As above, we perform this assignment first, before modifying any -- container state. Element_Type'Read (Stream, N (New_Node).Element); Container.Free := Container.Free - 1; end if; end Allocate; ------------ -- Append -- ------------ procedure Append (Container : in out List; New_Item : Element_Type; Count : Count_Type := 1) is begin Insert (Container, No_Element, New_Item, Count); end Append; ------------ -- Assign -- ------------ procedure Assign (Target : in out List; Source : List) is SN : Node_Array renames Source.Nodes; J : Count_Type; begin if Target'Address = Source'Address then return; end if; if Checks and then Target.Capacity < Source.Length then raise Capacity_Error -- ??? with "Target capacity is less than Source length"; end if; Target.Clear; J := Source.First; while J /= 0 loop Target.Append (SN (J).Element); J := SN (J).Next; end loop; end Assign; ----------- -- Clear -- ----------- procedure Clear (Container : in out List) is N : Node_Array renames Container.Nodes; X : Count_Type; begin if Container.Length = 0 then pragma Assert (Container.First = 0); pragma Assert (Container.Last = 0); pragma Assert (Container.TC = (Busy => 0, Lock => 0)); return; end if; pragma Assert (Container.First >= 1); pragma Assert (Container.Last >= 1); pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); TC_Check (Container.TC); while Container.Length > 1 loop X := Container.First; pragma Assert (N (N (X).Next).Prev = Container.First); Container.First := N (X).Next; N (Container.First).Prev := 0; Container.Length := Container.Length - 1; Free (Container, X); end loop; X := Container.First; pragma Assert (X = Container.Last); Container.First := 0; Container.Last := 0; Container.Length := 0; Free (Container, X); end Clear; ------------------------ -- Constant_Reference -- ------------------------ function Constant_Reference (Container : aliased List; Position : Cursor) return Constant_Reference_Type is begin if Checks and then Position.Container = null then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in Constant_Reference"); declare N : Node_Type renames Container.Nodes (Position.Node); TC : constant Tamper_Counts_Access := Container.TC'Unrestricted_Access; begin return R : constant Constant_Reference_Type := (Element => N.Element'Access, Control => (Controlled with TC)) do Lock (TC.all); end return; end; end Constant_Reference; -------------- -- Contains -- -------------- function Contains (Container : List; Item : Element_Type) return Boolean is begin return Find (Container, Item) /= No_Element; end Contains; ---------- -- Copy -- ---------- function Copy (Source : List; Capacity : Count_Type := 0) return List is C : Count_Type; begin if Capacity < Source.Length then if Checks and then Capacity /= 0 then raise Capacity_Error with "Requested capacity is less than Source length"; end if; C := Source.Length; else C := Capacity; end if; return Target : List (Capacity => C) do Assign (Target => Target, Source => Source); end return; end Copy; ------------ -- Delete -- ------------ procedure Delete (Container : in out List; Position : in out Cursor; Count : Count_Type := 1) is N : Node_Array renames Container.Nodes; X : Count_Type; begin if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in Delete"); pragma Assert (Container.First >= 1); pragma Assert (Container.Last >= 1); pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); if Position.Node = Container.First then Delete_First (Container, Count); Position := No_Element; return; end if; if Count = 0 then Position := No_Element; return; end if; TC_Check (Container.TC); for Index in 1 .. Count loop pragma Assert (Container.Length >= 2); X := Position.Node; Container.Length := Container.Length - 1; if X = Container.Last then Position := No_Element; Container.Last := N (X).Prev; N (Container.Last).Next := 0; Free (Container, X); return; end if; Position.Node := N (X).Next; N (N (X).Next).Prev := N (X).Prev; N (N (X).Prev).Next := N (X).Next; Free (Container, X); end loop; Position := No_Element; end Delete; ------------------ -- Delete_First -- ------------------ procedure Delete_First (Container : in out List; Count : Count_Type := 1) is N : Node_Array renames Container.Nodes; X : Count_Type; begin if Count >= Container.Length then Clear (Container); return; end if; if Count = 0 then return; end if; TC_Check (Container.TC); for J in 1 .. Count loop X := Container.First; pragma Assert (N (N (X).Next).Prev = Container.First); Container.First := N (X).Next; N (Container.First).Prev := 0; Container.Length := Container.Length - 1; Free (Container, X); end loop; end Delete_First; ----------------- -- Delete_Last -- ----------------- procedure Delete_Last (Container : in out List; Count : Count_Type := 1) is N : Node_Array renames Container.Nodes; X : Count_Type; begin if Count >= Container.Length then Clear (Container); return; end if; if Count = 0 then return; end if; TC_Check (Container.TC); for J in 1 .. Count loop X := Container.Last; pragma Assert (N (N (X).Prev).Next = Container.Last); Container.Last := N (X).Prev; N (Container.Last).Next := 0; Container.Length := Container.Length - 1; Free (Container, X); end loop; end Delete_Last; ------------- -- Element -- ------------- function Element (Position : Cursor) return Element_Type is begin if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; pragma Assert (Vet (Position), "bad cursor in Element"); return Position.Container.Nodes (Position.Node).Element; end Element; -------------- -- Finalize -- -------------- procedure Finalize (Object : in out Iterator) is begin if Object.Container /= null then Unbusy (Object.Container.TC); end if; end Finalize; ---------- -- Find -- ---------- function Find (Container : List; Item : Element_Type; Position : Cursor := No_Element) return Cursor is Nodes : Node_Array renames Container.Nodes; Node : Count_Type := Position.Node; begin if Node = 0 then Node := Container.First; else if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in Find"); end if; -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. declare Lock : With_Lock (Container.TC'Unrestricted_Access); begin while Node /= 0 loop if Nodes (Node).Element = Item then return Cursor'(Container'Unrestricted_Access, Node); end if; Node := Nodes (Node).Next; end loop; return No_Element; end; end Find; ----------- -- First -- ----------- function First (Container : List) return Cursor is begin if Container.First = 0 then return No_Element; else return Cursor'(Container'Unrestricted_Access, Container.First); end if; end First; function First (Object : Iterator) return Cursor is begin -- The value of the iterator object's Node component influences the -- behavior of the First (and Last) selector function. -- When the Node component is 0, this means the iterator object was -- constructed without a start expression, in which case the (forward) -- iteration starts from the (logical) beginning of the entire sequence -- of items (corresponding to Container.First, for a forward iterator). -- Otherwise, this is iteration over a partial sequence of items. When -- the Node component is positive, the iterator object was constructed -- with a start expression, that specifies the position from which the -- (forward) partial iteration begins. if Object.Node = 0 then return Bounded_Doubly_Linked_Lists.First (Object.Container.all); else return Cursor'(Object.Container, Object.Node); end if; end First; ------------------- -- First_Element -- ------------------- function First_Element (Container : List) return Element_Type is begin if Checks and then Container.First = 0 then raise Constraint_Error with "list is empty"; end if; return Container.Nodes (Container.First).Element; end First_Element; ---------- -- Free -- ---------- procedure Free (Container : in out List; X : Count_Type) is pragma Assert (X > 0); pragma Assert (X <= Container.Capacity); N : Node_Array renames Container.Nodes; pragma Assert (N (X).Prev >= 0); -- node is active begin -- The list container actually contains two lists: one for the "active" -- nodes that contain elements that have been inserted onto the list, -- and another for the "inactive" nodes for the free store. -- We desire that merely declaring an object should have only minimal -- cost; specially, we want to avoid having to initialize the free -- store (to fill in the links), especially if the capacity is large. -- The head of the free list is indicated by Container.Free. If its -- value is non-negative, then the free store has been initialized in -- the "normal" way: Container.Free points to the head of the list of -- free (inactive) nodes, and the value 0 means the free list is empty. -- Each node on the free list has been initialized to point to the next -- free node (via its Next component), and the value 0 means that this -- is the last free node. -- If Container.Free is negative, then the links on the free store have -- not been initialized. In this case the link values are implied: the -- free store comprises the components of the node array started with -- the absolute value of Container.Free, and continuing until the end of -- the array (Nodes'Last). -- If the list container is manipulated on one end only (for example if -- the container were being used as a stack), then there is no need to -- initialize the free store, since the inactive nodes are physically -- contiguous (in fact, they lie immediately beyond the logical end -- being manipulated). The only time we need to actually initialize the -- nodes in the free store is if the node that becomes inactive is not -- at the end of the list. The free store would then be discontiguous -- and so its nodes would need to be linked in the traditional way. -- ??? -- It might be possible to perform an optimization here. Suppose that -- the free store can be represented as having two parts: one comprising -- the non-contiguous inactive nodes linked together in the normal way, -- and the other comprising the contiguous inactive nodes (that are not -- linked together, at the end of the nodes array). This would allow us -- to never have to initialize the free store, except in a lazy way as -- nodes become inactive. -- When an element is deleted from the list container, its node becomes -- inactive, and so we set its Prev component to a negative value, to -- indicate that it is now inactive. This provides a useful way to -- detect a dangling cursor reference (and which is used in Vet). N (X).Prev := -1; -- Node is deallocated (not on active list) if Container.Free >= 0 then -- The free store has previously been initialized. All we need to -- do here is link the newly-free'd node onto the free list. N (X).Next := Container.Free; Container.Free := X; elsif X + 1 = abs Container.Free then -- The free store has not been initialized, and the node becoming -- inactive immediately precedes the start of the free store. All -- we need to do is move the start of the free store back by one. -- Note: initializing Next to zero is not strictly necessary but -- seems cleaner and marginally safer. N (X).Next := 0; Container.Free := Container.Free + 1; else -- The free store has not been initialized, and the node becoming -- inactive does not immediately precede the free store. Here we -- first initialize the free store (meaning the links are given -- values in the traditional way), and then link the newly-free'd -- node onto the head of the free store. -- ??? -- See the comments above for an optimization opportunity. If the -- next link for a node on the free store is negative, then this -- means the remaining nodes on the free store are physically -- contiguous, starting as the absolute value of that index value. Container.Free := abs Container.Free; if Container.Free > Container.Capacity then Container.Free := 0; else for I in Container.Free .. Container.Capacity - 1 loop N (I).Next := I + 1; end loop; N (Container.Capacity).Next := 0; end if; N (X).Next := Container.Free; Container.Free := X; end if; end Free; --------------------- -- Generic_Sorting -- --------------------- package body Generic_Sorting is --------------- -- Is_Sorted -- --------------- function Is_Sorted (Container : List) return Boolean is -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. Lock : With_Lock (Container.TC'Unrestricted_Access); Nodes : Node_Array renames Container.Nodes; Node : Count_Type; begin Node := Container.First; for J in 2 .. Container.Length loop if Nodes (Nodes (Node).Next).Element < Nodes (Node).Element then return False; end if; Node := Nodes (Node).Next; end loop; return True; end Is_Sorted; ----------- -- Merge -- ----------- procedure Merge (Target : in out List; Source : in out List) is begin -- The semantics of Merge changed slightly per AI05-0021. It was -- originally the case that if Target and Source denoted the same -- container object, then the GNAT implementation of Merge did -- nothing. However, it was argued that RM05 did not precisely -- specify the semantics for this corner case. The decision of the -- ARG was that if Target and Source denote the same non-empty -- container object, then Program_Error is raised. if Source.Is_Empty then return; end if; if Checks and then Target'Address = Source'Address then raise Program_Error with "Target and Source denote same non-empty container"; end if; if Checks and then Target.Length > Count_Type'Last - Source.Length then raise Constraint_Error with "new length exceeds maximum"; end if; if Checks and then Target.Length + Source.Length > Target.Capacity then raise Capacity_Error with "new length exceeds target capacity"; end if; TC_Check (Target.TC); TC_Check (Source.TC); -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. declare Lock_Target : With_Lock (Target.TC'Unchecked_Access); Lock_Source : With_Lock (Source.TC'Unchecked_Access); LN : Node_Array renames Target.Nodes; RN : Node_Array renames Source.Nodes; LI, LJ, RI, RJ : Count_Type; begin LI := Target.First; RI := Source.First; while RI /= 0 loop pragma Assert (RN (RI).Next = 0 or else not (RN (RN (RI).Next).Element < RN (RI).Element)); if LI = 0 then Splice_Internal (Target, 0, Source); exit; end if; pragma Assert (LN (LI).Next = 0 or else not (LN (LN (LI).Next).Element < LN (LI).Element)); if RN (RI).Element < LN (LI).Element then RJ := RI; RI := RN (RI).Next; Splice_Internal (Target, LI, Source, RJ, LJ); else LI := LN (LI).Next; end if; end loop; end; end Merge; ---------- -- Sort -- ---------- procedure Sort (Container : in out List) is N : Node_Array renames Container.Nodes; procedure Partition (Pivot, Back : Count_Type); -- What does this do ??? procedure Sort (Front, Back : Count_Type); -- Internal procedure, what does it do??? rename it??? --------------- -- Partition -- --------------- procedure Partition (Pivot, Back : Count_Type) is Node : Count_Type; begin Node := N (Pivot).Next; while Node /= Back loop if N (Node).Element < N (Pivot).Element then declare Prev : constant Count_Type := N (Node).Prev; Next : constant Count_Type := N (Node).Next; begin N (Prev).Next := Next; if Next = 0 then Container.Last := Prev; else N (Next).Prev := Prev; end if; N (Node).Next := Pivot; N (Node).Prev := N (Pivot).Prev; N (Pivot).Prev := Node; if N (Node).Prev = 0 then Container.First := Node; else N (N (Node).Prev).Next := Node; end if; Node := Next; end; else Node := N (Node).Next; end if; end loop; end Partition; ---------- -- Sort -- ---------- procedure Sort (Front, Back : Count_Type) is Pivot : constant Count_Type := (if Front = 0 then Container.First else N (Front).Next); begin if Pivot /= Back then Partition (Pivot, Back); Sort (Front, Pivot); Sort (Pivot, Back); end if; end Sort; -- Start of processing for Sort begin if Container.Length <= 1 then return; end if; pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); TC_Check (Container.TC); -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. declare Lock : With_Lock (Container.TC'Unchecked_Access); begin Sort (Front => 0, Back => 0); end; pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); end Sort; end Generic_Sorting; ------------------------ -- Get_Element_Access -- ------------------------ function Get_Element_Access (Position : Cursor) return not null Element_Access is begin return Position.Container.Nodes (Position.Node).Element'Access; end Get_Element_Access; ----------------- -- Has_Element -- ----------------- function Has_Element (Position : Cursor) return Boolean is begin pragma Assert (Vet (Position), "bad cursor in Has_Element"); return Position.Node /= 0; end Has_Element; ------------ -- Insert -- ------------ procedure Insert (Container : in out List; Before : Cursor; New_Item : Element_Type; Position : out Cursor; Count : Count_Type := 1) is First_Node : Count_Type; New_Node : Count_Type; begin if Before.Container /= null then if Checks and then Before.Container /= Container'Unrestricted_Access then raise Program_Error with "Before cursor designates wrong list"; end if; pragma Assert (Vet (Before), "bad cursor in Insert"); end if; if Count = 0 then Position := Before; return; end if; if Checks and then Container.Length > Container.Capacity - Count then raise Capacity_Error with "capacity exceeded"; end if; TC_Check (Container.TC); Allocate (Container, New_Item, New_Node); First_Node := New_Node; Insert_Internal (Container, Before.Node, New_Node); for Index in Count_Type'(2) .. Count loop Allocate (Container, New_Item, New_Node); Insert_Internal (Container, Before.Node, New_Node); end loop; Position := Cursor'(Container'Unchecked_Access, First_Node); end Insert; procedure Insert (Container : in out List; Before : Cursor; New_Item : Element_Type; Count : Count_Type := 1) is Position : Cursor; pragma Unreferenced (Position); begin Insert (Container, Before, New_Item, Position, Count); end Insert; procedure Insert (Container : in out List; Before : Cursor; Position : out Cursor; Count : Count_Type := 1) is pragma Warnings (Off); Default_Initialized_Item : Element_Type; pragma Unmodified (Default_Initialized_Item); -- OK to reference, see below. Note that we need to suppress both the -- front end warning and the back end warning. In addition, pragma -- Unmodified is needed to suppress the warning ``actual type for -- "Element_Type" should be fully initialized type'' on certain -- instantiations. begin -- There is no explicit element provided, but in an instance the element -- type may be a scalar with a Default_Value aspect, or a composite -- type with such a scalar component, or components with default -- initialization, so insert the specified number of possibly -- initialized elements at the given position. Insert (Container, Before, Default_Initialized_Item, Position, Count); pragma Warnings (On); end Insert; --------------------- -- Insert_Internal -- --------------------- procedure Insert_Internal (Container : in out List; Before : Count_Type; New_Node : Count_Type) is N : Node_Array renames Container.Nodes; begin if Container.Length = 0 then pragma Assert (Before = 0); pragma Assert (Container.First = 0); pragma Assert (Container.Last = 0); Container.First := New_Node; N (Container.First).Prev := 0; Container.Last := New_Node; N (Container.Last).Next := 0; -- Before = zero means append elsif Before = 0 then pragma Assert (N (Container.Last).Next = 0); N (Container.Last).Next := New_Node; N (New_Node).Prev := Container.Last; Container.Last := New_Node; N (Container.Last).Next := 0; -- Before = Container.First means prepend elsif Before = Container.First then pragma Assert (N (Container.First).Prev = 0); N (Container.First).Prev := New_Node; N (New_Node).Next := Container.First; Container.First := New_Node; N (Container.First).Prev := 0; else pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); N (New_Node).Next := Before; N (New_Node).Prev := N (Before).Prev; N (N (Before).Prev).Next := New_Node; N (Before).Prev := New_Node; end if; Container.Length := Container.Length + 1; end Insert_Internal; -------------- -- Is_Empty -- -------------- function Is_Empty (Container : List) return Boolean is begin return Container.Length = 0; end Is_Empty; ------------- -- Iterate -- ------------- procedure Iterate (Container : List; Process : not null access procedure (Position : Cursor)) is Busy : With_Busy (Container.TC'Unrestricted_Access); Node : Count_Type := Container.First; begin while Node /= 0 loop Process (Cursor'(Container'Unrestricted_Access, Node)); Node := Container.Nodes (Node).Next; end loop; end Iterate; function Iterate (Container : List) return List_Iterator_Interfaces.Reversible_Iterator'Class is begin -- The value of the Node component influences the behavior of the First -- and Last selector functions of the iterator object. When the Node -- component is 0 (as is the case here), this means the iterator -- object was constructed without a start expression. This is a -- complete iterator, meaning that the iteration starts from the -- (logical) beginning of the sequence of items. -- Note: For a forward iterator, Container.First is the beginning, and -- for a reverse iterator, Container.Last is the beginning. return It : constant Iterator := Iterator'(Limited_Controlled with Container => Container'Unrestricted_Access, Node => 0) do Busy (Container.TC'Unrestricted_Access.all); end return; end Iterate; function Iterate (Container : List; Start : Cursor) return List_Iterator_Interfaces.Reversible_Iterator'class is begin -- It was formerly the case that when Start = No_Element, the partial -- iterator was defined to behave the same as for a complete iterator, -- and iterate over the entire sequence of items. However, those -- semantics were unintuitive and arguably error-prone (it is too easy -- to accidentally create an endless loop), and so they were changed, -- per the ARG meeting in Denver on 2011/11. However, there was no -- consensus about what positive meaning this corner case should have, -- and so it was decided to simply raise an exception. This does imply, -- however, that it is not possible to use a partial iterator to specify -- an empty sequence of items. if Checks and then Start = No_Element then raise Constraint_Error with "Start position for iterator equals No_Element"; end if; if Checks and then Start.Container /= Container'Unrestricted_Access then raise Program_Error with "Start cursor of Iterate designates wrong list"; end if; pragma Assert (Vet (Start), "Start cursor of Iterate is bad"); -- The value of the Node component influences the behavior of the First -- and Last selector functions of the iterator object. When the Node -- component is positive (as is the case here), it means that this -- is a partial iteration, over a subset of the complete sequence of -- items. The iterator object was constructed with a start expression, -- indicating the position from which the iteration begins. Note that -- the start position has the same value irrespective of whether this -- is a forward or reverse iteration. return It : constant Iterator := Iterator'(Limited_Controlled with Container => Container'Unrestricted_Access, Node => Start.Node) do Busy (Container.TC'Unrestricted_Access.all); end return; end Iterate; ---------- -- Last -- ---------- function Last (Container : List) return Cursor is begin if Container.Last = 0 then return No_Element; else return Cursor'(Container'Unrestricted_Access, Container.Last); end if; end Last; function Last (Object : Iterator) return Cursor is begin -- The value of the iterator object's Node component influences the -- behavior of the Last (and First) selector function. -- When the Node component is 0, this means the iterator object was -- constructed without a start expression, in which case the (reverse) -- iteration starts from the (logical) beginning of the entire sequence -- (corresponding to Container.Last, for a reverse iterator). -- Otherwise, this is iteration over a partial sequence of items. When -- the Node component is positive, the iterator object was constructed -- with a start expression, that specifies the position from which the -- (reverse) partial iteration begins. if Object.Node = 0 then return Bounded_Doubly_Linked_Lists.Last (Object.Container.all); else return Cursor'(Object.Container, Object.Node); end if; end Last; ------------------ -- Last_Element -- ------------------ function Last_Element (Container : List) return Element_Type is begin if Checks and then Container.Last = 0 then raise Constraint_Error with "list is empty"; end if; return Container.Nodes (Container.Last).Element; end Last_Element; ------------ -- Length -- ------------ function Length (Container : List) return Count_Type is begin return Container.Length; end Length; ---------- -- Move -- ---------- procedure Move (Target : in out List; Source : in out List) is N : Node_Array renames Source.Nodes; X : Count_Type; begin if Target'Address = Source'Address then return; end if; if Checks and then Target.Capacity < Source.Length then raise Capacity_Error with "Source length exceeds Target capacity"; end if; TC_Check (Source.TC); -- Clear target, note that this checks busy bits of Target Clear (Target); while Source.Length > 1 loop pragma Assert (Source.First in 1 .. Source.Capacity); pragma Assert (Source.Last /= Source.First); pragma Assert (N (Source.First).Prev = 0); pragma Assert (N (Source.Last).Next = 0); -- Copy first element from Source to Target X := Source.First; Append (Target, N (X).Element); -- Unlink first node of Source Source.First := N (X).Next; N (Source.First).Prev := 0; Source.Length := Source.Length - 1; -- The representation invariants for Source have been restored. It is -- now safe to free the unlinked node, without fear of corrupting the -- active links of Source. -- Note that the algorithm we use here models similar algorithms used -- in the unbounded form of the doubly-linked list container. In that -- case, Free is an instantation of Unchecked_Deallocation, which can -- fail (because PE will be raised if controlled Finalize fails), so -- we must defer the call until the last step. Here in the bounded -- form, Free merely links the node we have just "deallocated" onto a -- list of inactive nodes, so technically Free cannot fail. However, -- for consistency, we handle Free the same way here as we do for the -- unbounded form, with the pessimistic assumption that it can fail. Free (Source, X); end loop; if Source.Length = 1 then pragma Assert (Source.First in 1 .. Source.Capacity); pragma Assert (Source.Last = Source.First); pragma Assert (N (Source.First).Prev = 0); pragma Assert (N (Source.Last).Next = 0); -- Copy element from Source to Target X := Source.First; Append (Target, N (X).Element); -- Unlink node of Source Source.First := 0; Source.Last := 0; Source.Length := 0; -- Return the unlinked node to the free store Free (Source, X); end if; end Move; ---------- -- Next -- ---------- procedure Next (Position : in out Cursor) is begin Position := Next (Position); end Next; function Next (Position : Cursor) return Cursor is begin if Position.Node = 0 then return No_Element; end if; pragma Assert (Vet (Position), "bad cursor in Next"); declare Nodes : Node_Array renames Position.Container.Nodes; Node : constant Count_Type := Nodes (Position.Node).Next; begin if Node = 0 then return No_Element; else return Cursor'(Position.Container, Node); end if; end; end Next; function Next (Object : Iterator; Position : Cursor) return Cursor is begin if Position.Container = null then return No_Element; end if; if Checks and then Position.Container /= Object.Container then raise Program_Error with "Position cursor of Next designates wrong list"; end if; return Next (Position); end Next; ------------- -- Prepend -- ------------- procedure Prepend (Container : in out List; New_Item : Element_Type; Count : Count_Type := 1) is begin Insert (Container, First (Container), New_Item, Count); end Prepend; -------------- -- Previous -- -------------- procedure Previous (Position : in out Cursor) is begin Position := Previous (Position); end Previous; function Previous (Position : Cursor) return Cursor is begin if Position.Node = 0 then return No_Element; end if; pragma Assert (Vet (Position), "bad cursor in Previous"); declare Nodes : Node_Array renames Position.Container.Nodes; Node : constant Count_Type := Nodes (Position.Node).Prev; begin if Node = 0 then return No_Element; else return Cursor'(Position.Container, Node); end if; end; end Previous; function Previous (Object : Iterator; Position : Cursor) return Cursor is begin if Position.Container = null then return No_Element; end if; if Checks and then Position.Container /= Object.Container then raise Program_Error with "Position cursor of Previous designates wrong list"; end if; return Previous (Position); end Previous; ---------------------- -- Pseudo_Reference -- ---------------------- function Pseudo_Reference (Container : aliased List'Class) return Reference_Control_Type is TC : constant Tamper_Counts_Access := Container.TC'Unrestricted_Access; begin return R : constant Reference_Control_Type := (Controlled with TC) do Lock (TC.all); end return; end Pseudo_Reference; ------------------- -- Query_Element -- ------------------- procedure Query_Element (Position : Cursor; Process : not null access procedure (Element : Element_Type)) is begin if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; pragma Assert (Vet (Position), "bad cursor in Query_Element"); declare Lock : With_Lock (Position.Container.TC'Unrestricted_Access); C : List renames Position.Container.all'Unrestricted_Access.all; N : Node_Type renames C.Nodes (Position.Node); begin Process (N.Element); end; end Query_Element; ---------- -- Read -- ---------- procedure Read (Stream : not null access Root_Stream_Type'Class; Item : out List) is N : Count_Type'Base; X : Count_Type; begin Clear (Item); Count_Type'Base'Read (Stream, N); if Checks and then N < 0 then raise Program_Error with "bad list length (corrupt stream)"; end if; if N = 0 then return; end if; if Checks and then N > Item.Capacity then raise Constraint_Error with "length exceeds capacity"; end if; for Idx in 1 .. N loop Allocate (Item, Stream, New_Node => X); Insert_Internal (Item, Before => 0, New_Node => X); end loop; end Read; procedure Read (Stream : not null access Root_Stream_Type'Class; Item : out Cursor) is begin raise Program_Error with "attempt to stream list cursor"; end Read; procedure Read (Stream : not null access Root_Stream_Type'Class; Item : out Reference_Type) is begin raise Program_Error with "attempt to stream reference"; end Read; procedure Read (Stream : not null access Root_Stream_Type'Class; Item : out Constant_Reference_Type) is begin raise Program_Error with "attempt to stream reference"; end Read; --------------- -- Reference -- --------------- function Reference (Container : aliased in out List; Position : Cursor) return Reference_Type is begin if Checks and then Position.Container = null then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in function Reference"); declare N : Node_Type renames Container.Nodes (Position.Node); TC : constant Tamper_Counts_Access := Container.TC'Unrestricted_Access; begin return R : constant Reference_Type := (Element => N.Element'Access, Control => (Controlled with TC)) do Lock (TC.all); end return; end; end Reference; --------------------- -- Replace_Element -- --------------------- procedure Replace_Element (Container : in out List; Position : Cursor; New_Item : Element_Type) is begin if Checks and then Position.Container = null then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unchecked_Access then raise Program_Error with "Position cursor designates wrong container"; end if; TE_Check (Container.TC); pragma Assert (Vet (Position), "bad cursor in Replace_Element"); Container.Nodes (Position.Node).Element := New_Item; end Replace_Element; ---------------------- -- Reverse_Elements -- ---------------------- procedure Reverse_Elements (Container : in out List) is N : Node_Array renames Container.Nodes; I : Count_Type := Container.First; J : Count_Type := Container.Last; procedure Swap (L, R : Count_Type); ---------- -- Swap -- ---------- procedure Swap (L, R : Count_Type) is LN : constant Count_Type := N (L).Next; LP : constant Count_Type := N (L).Prev; RN : constant Count_Type := N (R).Next; RP : constant Count_Type := N (R).Prev; begin if LP /= 0 then N (LP).Next := R; end if; if RN /= 0 then N (RN).Prev := L; end if; N (L).Next := RN; N (R).Prev := LP; if LN = R then pragma Assert (RP = L); N (L).Prev := R; N (R).Next := L; else N (L).Prev := RP; N (RP).Next := L; N (R).Next := LN; N (LN).Prev := R; end if; end Swap; -- Start of processing for Reverse_Elements begin if Container.Length <= 1 then return; end if; pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); TC_Check (Container.TC); Container.First := J; Container.Last := I; loop Swap (L => I, R => J); J := N (J).Next; exit when I = J; I := N (I).Prev; exit when I = J; Swap (L => J, R => I); I := N (I).Next; exit when I = J; J := N (J).Prev; exit when I = J; end loop; pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); end Reverse_Elements; ------------------ -- Reverse_Find -- ------------------ function Reverse_Find (Container : List; Item : Element_Type; Position : Cursor := No_Element) return Cursor is Node : Count_Type := Position.Node; begin if Node = 0 then Node := Container.Last; else if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in Reverse_Find"); end if; -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. declare Lock : With_Lock (Container.TC'Unrestricted_Access); begin while Node /= 0 loop if Container.Nodes (Node).Element = Item then return Cursor'(Container'Unrestricted_Access, Node); end if; Node := Container.Nodes (Node).Prev; end loop; return No_Element; end; end Reverse_Find; --------------------- -- Reverse_Iterate -- --------------------- procedure Reverse_Iterate (Container : List; Process : not null access procedure (Position : Cursor)) is Busy : With_Busy (Container.TC'Unrestricted_Access); Node : Count_Type := Container.Last; begin while Node /= 0 loop Process (Cursor'(Container'Unrestricted_Access, Node)); Node := Container.Nodes (Node).Prev; end loop; end Reverse_Iterate; ------------ -- Splice -- ------------ procedure Splice (Target : in out List; Before : Cursor; Source : in out List) is begin if Before.Container /= null then if Checks and then Before.Container /= Target'Unrestricted_Access then raise Program_Error with "Before cursor designates wrong container"; end if; pragma Assert (Vet (Before), "bad cursor in Splice"); end if; if Target'Address = Source'Address or else Source.Length = 0 then return; end if; if Checks and then Target.Length > Count_Type'Last - Source.Length then raise Constraint_Error with "new length exceeds maximum"; end if; if Checks and then Target.Length + Source.Length > Target.Capacity then raise Capacity_Error with "new length exceeds target capacity"; end if; TC_Check (Target.TC); TC_Check (Source.TC); Splice_Internal (Target, Before.Node, Source); end Splice; procedure Splice (Container : in out List; Before : Cursor; Position : Cursor) is N : Node_Array renames Container.Nodes; begin if Before.Container /= null then if Checks and then Before.Container /= Container'Unchecked_Access then raise Program_Error with "Before cursor designates wrong container"; end if; pragma Assert (Vet (Before), "bad Before cursor in Splice"); end if; if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad Position cursor in Splice"); if Position.Node = Before.Node or else N (Position.Node).Next = Before.Node then return; end if; pragma Assert (Container.Length >= 2); TC_Check (Container.TC); if Before.Node = 0 then pragma Assert (Position.Node /= Container.Last); if Position.Node = Container.First then Container.First := N (Position.Node).Next; N (Container.First).Prev := 0; else N (N (Position.Node).Prev).Next := N (Position.Node).Next; N (N (Position.Node).Next).Prev := N (Position.Node).Prev; end if; N (Container.Last).Next := Position.Node; N (Position.Node).Prev := Container.Last; Container.Last := Position.Node; N (Container.Last).Next := 0; return; end if; if Before.Node = Container.First then pragma Assert (Position.Node /= Container.First); if Position.Node = Container.Last then Container.Last := N (Position.Node).Prev; N (Container.Last).Next := 0; else N (N (Position.Node).Prev).Next := N (Position.Node).Next; N (N (Position.Node).Next).Prev := N (Position.Node).Prev; end if; N (Container.First).Prev := Position.Node; N (Position.Node).Next := Container.First; Container.First := Position.Node; N (Container.First).Prev := 0; return; end if; if Position.Node = Container.First then Container.First := N (Position.Node).Next; N (Container.First).Prev := 0; elsif Position.Node = Container.Last then Container.Last := N (Position.Node).Prev; N (Container.Last).Next := 0; else N (N (Position.Node).Prev).Next := N (Position.Node).Next; N (N (Position.Node).Next).Prev := N (Position.Node).Prev; end if; N (N (Before.Node).Prev).Next := Position.Node; N (Position.Node).Prev := N (Before.Node).Prev; N (Before.Node).Prev := Position.Node; N (Position.Node).Next := Before.Node; pragma Assert (N (Container.First).Prev = 0); pragma Assert (N (Container.Last).Next = 0); end Splice; procedure Splice (Target : in out List; Before : Cursor; Source : in out List; Position : in out Cursor) is Target_Position : Count_Type; begin if Target'Address = Source'Address then Splice (Target, Before, Position); return; end if; if Before.Container /= null then if Checks and then Before.Container /= Target'Unrestricted_Access then raise Program_Error with "Before cursor designates wrong container"; end if; pragma Assert (Vet (Before), "bad Before cursor in Splice"); end if; if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Source'Unrestricted_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad Position cursor in Splice"); if Checks and then Target.Length >= Target.Capacity then raise Capacity_Error with "Target is full"; end if; TC_Check (Target.TC); TC_Check (Source.TC); Splice_Internal (Target => Target, Before => Before.Node, Source => Source, Src_Pos => Position.Node, Tgt_Pos => Target_Position); Position := Cursor'(Target'Unrestricted_Access, Target_Position); end Splice; --------------------- -- Splice_Internal -- --------------------- procedure Splice_Internal (Target : in out List; Before : Count_Type; Source : in out List) is N : Node_Array renames Source.Nodes; X : Count_Type; begin -- This implements the corresponding Splice operation, after the -- parameters have been vetted, and corner-cases disposed of. pragma Assert (Target'Address /= Source'Address); pragma Assert (Source.Length > 0); pragma Assert (Source.First /= 0); pragma Assert (N (Source.First).Prev = 0); pragma Assert (Source.Last /= 0); pragma Assert (N (Source.Last).Next = 0); pragma Assert (Target.Length <= Count_Type'Last - Source.Length); pragma Assert (Target.Length + Source.Length <= Target.Capacity); while Source.Length > 1 loop -- Copy first element of Source onto Target Allocate (Target, N (Source.First).Element, New_Node => X); Insert_Internal (Target, Before => Before, New_Node => X); -- Unlink the first node from Source X := Source.First; pragma Assert (N (N (X).Next).Prev = X); Source.First := N (X).Next; N (Source.First).Prev := 0; Source.Length := Source.Length - 1; -- Return the Source node to its free store Free (Source, X); end loop; -- Copy first (and only remaining) element of Source onto Target Allocate (Target, N (Source.First).Element, New_Node => X); Insert_Internal (Target, Before => Before, New_Node => X); -- Unlink the node from Source X := Source.First; pragma Assert (X = Source.Last); Source.First := 0; Source.Last := 0; Source.Length := 0; -- Return the Source node to its free store Free (Source, X); end Splice_Internal; procedure Splice_Internal (Target : in out List; Before : Count_Type; -- node of Target Source : in out List; Src_Pos : Count_Type; -- node of Source Tgt_Pos : out Count_Type) is N : Node_Array renames Source.Nodes; begin -- This implements the corresponding Splice operation, after the -- parameters have been vetted, and corner-cases handled. pragma Assert (Target'Address /= Source'Address); pragma Assert (Target.Length < Target.Capacity); pragma Assert (Source.Length > 0); pragma Assert (Source.First /= 0); pragma Assert (N (Source.First).Prev = 0); pragma Assert (Source.Last /= 0); pragma Assert (N (Source.Last).Next = 0); pragma Assert (Src_Pos /= 0); Allocate (Target, N (Src_Pos).Element, New_Node => Tgt_Pos); Insert_Internal (Target, Before => Before, New_Node => Tgt_Pos); if Source.Length = 1 then pragma Assert (Source.First = Source.Last); pragma Assert (Src_Pos = Source.First); Source.First := 0; Source.Last := 0; elsif Src_Pos = Source.First then pragma Assert (N (N (Src_Pos).Next).Prev = Src_Pos); Source.First := N (Src_Pos).Next; N (Source.First).Prev := 0; elsif Src_Pos = Source.Last then pragma Assert (N (N (Src_Pos).Prev).Next = Src_Pos); Source.Last := N (Src_Pos).Prev; N (Source.Last).Next := 0; else pragma Assert (Source.Length >= 3); pragma Assert (N (N (Src_Pos).Next).Prev = Src_Pos); pragma Assert (N (N (Src_Pos).Prev).Next = Src_Pos); N (N (Src_Pos).Next).Prev := N (Src_Pos).Prev; N (N (Src_Pos).Prev).Next := N (Src_Pos).Next; end if; Source.Length := Source.Length - 1; Free (Source, Src_Pos); end Splice_Internal; ---------- -- Swap -- ---------- procedure Swap (Container : in out List; I, J : Cursor) is begin if Checks and then I.Node = 0 then raise Constraint_Error with "I cursor has no element"; end if; if Checks and then J.Node = 0 then raise Constraint_Error with "J cursor has no element"; end if; if Checks and then I.Container /= Container'Unchecked_Access then raise Program_Error with "I cursor designates wrong container"; end if; if Checks and then J.Container /= Container'Unchecked_Access then raise Program_Error with "J cursor designates wrong container"; end if; if I.Node = J.Node then return; end if; TE_Check (Container.TC); pragma Assert (Vet (I), "bad I cursor in Swap"); pragma Assert (Vet (J), "bad J cursor in Swap"); declare EI : Element_Type renames Container.Nodes (I.Node).Element; EJ : Element_Type renames Container.Nodes (J.Node).Element; EI_Copy : constant Element_Type := EI; begin EI := EJ; EJ := EI_Copy; end; end Swap; ---------------- -- Swap_Links -- ---------------- procedure Swap_Links (Container : in out List; I, J : Cursor) is begin if Checks and then I.Node = 0 then raise Constraint_Error with "I cursor has no element"; end if; if Checks and then J.Node = 0 then raise Constraint_Error with "J cursor has no element"; end if; if Checks and then I.Container /= Container'Unrestricted_Access then raise Program_Error with "I cursor designates wrong container"; end if; if Checks and then J.Container /= Container'Unrestricted_Access then raise Program_Error with "J cursor designates wrong container"; end if; if I.Node = J.Node then return; end if; TC_Check (Container.TC); pragma Assert (Vet (I), "bad I cursor in Swap_Links"); pragma Assert (Vet (J), "bad J cursor in Swap_Links"); declare I_Next : constant Cursor := Next (I); begin if I_Next = J then Splice (Container, Before => I, Position => J); else declare J_Next : constant Cursor := Next (J); begin if J_Next = I then Splice (Container, Before => J, Position => I); else pragma Assert (Container.Length >= 3); Splice (Container, Before => I_Next, Position => J); Splice (Container, Before => J_Next, Position => I); end if; end; end if; end; end Swap_Links; -------------------- -- Update_Element -- -------------------- procedure Update_Element (Container : in out List; Position : Cursor; Process : not null access procedure (Element : in out Element_Type)) is begin if Checks and then Position.Node = 0 then raise Constraint_Error with "Position cursor has no element"; end if; if Checks and then Position.Container /= Container'Unchecked_Access then raise Program_Error with "Position cursor designates wrong container"; end if; pragma Assert (Vet (Position), "bad cursor in Update_Element"); declare Lock : With_Lock (Container.TC'Unchecked_Access); N : Node_Type renames Container.Nodes (Position.Node); begin Process (N.Element); end; end Update_Element; --------- -- Vet -- --------- function Vet (Position : Cursor) return Boolean is begin if Position.Node = 0 then return Position.Container = null; end if; if Position.Container = null then return False; end if; declare L : List renames Position.Container.all; N : Node_Array renames L.Nodes; begin if L.Length = 0 then return False; end if; if L.First = 0 or L.First > L.Capacity then return False; end if; if L.Last = 0 or L.Last > L.Capacity then return False; end if; if N (L.First).Prev /= 0 then return False; end if; if N (L.Last).Next /= 0 then return False; end if; if Position.Node > L.Capacity then return False; end if; -- An invariant of an active node is that its Previous and Next -- components are non-negative. Operation Free sets the Previous -- component of the node to the value -1 before actually deallocating -- the node, to mark the node as inactive. (By "dellocating" we mean -- only that the node is linked onto a list of inactive nodes used -- for storage.) This marker gives us a simple way to detect a -- dangling reference to a node. if N (Position.Node).Prev < 0 then -- see Free return False; end if; if N (Position.Node).Prev > L.Capacity then return False; end if; if N (Position.Node).Next = Position.Node then return False; end if; if N (Position.Node).Prev = Position.Node then return False; end if; if N (Position.Node).Prev = 0 and then Position.Node /= L.First then return False; end if; pragma Assert (N (Position.Node).Prev /= 0 or else Position.Node = L.First); if N (Position.Node).Next = 0 and then Position.Node /= L.Last then return False; end if; pragma Assert (N (Position.Node).Next /= 0 or else Position.Node = L.Last); if L.Length = 1 then return L.First = L.Last; end if; if L.First = L.Last then return False; end if; if N (L.First).Next = 0 then return False; end if; if N (L.Last).Prev = 0 then return False; end if; if N (N (L.First).Next).Prev /= L.First then return False; end if; if N (N (L.Last).Prev).Next /= L.Last then return False; end if; if L.Length = 2 then if N (L.First).Next /= L.Last then return False; end if; if N (L.Last).Prev /= L.First then return False; end if; return True; end if; if N (L.First).Next = L.Last then return False; end if; if N (L.Last).Prev = L.First then return False; end if; -- Eliminate earlier possibility if Position.Node = L.First then return True; end if; pragma Assert (N (Position.Node).Prev /= 0); -- Eliminate another possibility if Position.Node = L.Last then return True; end if; pragma Assert (N (Position.Node).Next /= 0); if N (N (Position.Node).Next).Prev /= Position.Node then return False; end if; if N (N (Position.Node).Prev).Next /= Position.Node then return False; end if; if L.Length = 3 then if N (L.First).Next /= Position.Node then return False; end if; if N (L.Last).Prev /= Position.Node then return False; end if; end if; return True; end; end Vet; ----------- -- Write -- ----------- procedure Write (Stream : not null access Root_Stream_Type'Class; Item : List) is Node : Count_Type; begin Count_Type'Base'Write (Stream, Item.Length); Node := Item.First; while Node /= 0 loop Element_Type'Write (Stream, Item.Nodes (Node).Element); Node := Item.Nodes (Node).Next; end loop; end Write; procedure Write (Stream : not null access Root_Stream_Type'Class; Item : Cursor) is begin raise Program_Error with "attempt to stream list cursor"; end Write; procedure Write (Stream : not null access Root_Stream_Type'Class; Item : Reference_Type) is begin raise Program_Error with "attempt to stream reference"; end Write; procedure Write (Stream : not null access Root_Stream_Type'Class; Item : Constant_Reference_Type) is begin raise Program_Error with "attempt to stream reference"; end Write; end Ada.Containers.Bounded_Doubly_Linked_Lists;