------------------------------------------------------------------------------ -- -- -- GNAT LIBRARY COMPONENTS -- -- -- -- ADA.CONTAINERS.HASH_TABLES.GENERIC_BOUNDED_KEYS -- -- -- -- B o d y -- -- -- -- Copyright (C) 2004-2013, 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. -- ------------------------------------------------------------------------------ package body Ada.Containers.Hash_Tables.Generic_Bounded_Keys is ----------------------------- -- Checked_Equivalent_Keys -- ----------------------------- function Checked_Equivalent_Keys (HT : aliased in out Hash_Table_Type'Class; Key : Key_Type; Node : Count_Type) return Boolean is Result : Boolean; B : Natural renames HT.Busy; L : Natural renames HT.Lock; begin B := B + 1; L := L + 1; Result := Equivalent_Keys (Key, HT.Nodes (Node)); B := B - 1; L := L - 1; return Result; exception when others => B := B - 1; L := L - 1; raise; end Checked_Equivalent_Keys; ------------------- -- Checked_Index -- ------------------- function Checked_Index (HT : aliased in out Hash_Table_Type'Class; Key : Key_Type) return Hash_Type is Result : Hash_Type; B : Natural renames HT.Busy; L : Natural renames HT.Lock; begin B := B + 1; L := L + 1; Result := HT.Buckets'First + Hash (Key) mod HT.Buckets'Length; B := B - 1; L := L - 1; return Result; exception when others => B := B - 1; L := L - 1; raise; end Checked_Index; -------------------------- -- Delete_Key_Sans_Free -- -------------------------- procedure Delete_Key_Sans_Free (HT : in out Hash_Table_Type'Class; Key : Key_Type; X : out Count_Type) is Indx : Hash_Type; Prev : Count_Type; begin if HT.Length = 0 then X := 0; return; end if; -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. if HT.Busy > 0 then raise Program_Error with "attempt to tamper with cursors (container is busy)"; end if; Indx := Checked_Index (HT, Key); X := HT.Buckets (Indx); if X = 0 then return; end if; if Checked_Equivalent_Keys (HT, Key, X) then if HT.Busy > 0 then raise Program_Error with "attempt to tamper with cursors (container is busy)"; end if; HT.Buckets (Indx) := Next (HT.Nodes (X)); HT.Length := HT.Length - 1; return; end if; loop Prev := X; X := Next (HT.Nodes (Prev)); if X = 0 then return; end if; if Checked_Equivalent_Keys (HT, Key, X) then if HT.Busy > 0 then raise Program_Error with "attempt to tamper with cursors (container is busy)"; end if; Set_Next (HT.Nodes (Prev), Next => Next (HT.Nodes (X))); HT.Length := HT.Length - 1; return; end if; end loop; end Delete_Key_Sans_Free; ---------- -- Find -- ---------- function Find (HT : Hash_Table_Type'Class; Key : Key_Type) return Count_Type is Indx : Hash_Type; Node : Count_Type; begin if HT.Length = 0 then return 0; end if; Indx := Checked_Index (HT'Unrestricted_Access.all, Key); Node := HT.Buckets (Indx); while Node /= 0 loop if Checked_Equivalent_Keys (HT'Unrestricted_Access.all, Key, Node) then return Node; end if; Node := Next (HT.Nodes (Node)); end loop; return 0; end Find; -------------------------------- -- Generic_Conditional_Insert -- -------------------------------- procedure Generic_Conditional_Insert (HT : in out Hash_Table_Type'Class; Key : Key_Type; Node : out Count_Type; Inserted : out Boolean) is Indx : Hash_Type; begin -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. if HT.Busy > 0 then raise Program_Error with "attempt to tamper with cursors (container is busy)"; end if; Indx := Checked_Index (HT, Key); Node := HT.Buckets (Indx); if Node = 0 then if HT.Length = HT.Capacity then raise Capacity_Error with "no more capacity for insertion"; end if; Node := New_Node; Set_Next (HT.Nodes (Node), Next => 0); Inserted := True; HT.Buckets (Indx) := Node; HT.Length := HT.Length + 1; return; end if; loop if Checked_Equivalent_Keys (HT, Key, Node) then Inserted := False; return; end if; Node := Next (HT.Nodes (Node)); exit when Node = 0; end loop; if HT.Length = HT.Capacity then raise Capacity_Error with "no more capacity for insertion"; end if; Node := New_Node; Set_Next (HT.Nodes (Node), Next => HT.Buckets (Indx)); Inserted := True; HT.Buckets (Indx) := Node; HT.Length := HT.Length + 1; end Generic_Conditional_Insert; ----------------------------- -- Generic_Replace_Element -- ----------------------------- procedure Generic_Replace_Element (HT : in out Hash_Table_Type'Class; Node : Count_Type; Key : Key_Type) is pragma Assert (HT.Length > 0); pragma Assert (Node /= 0); BB : Buckets_Type renames HT.Buckets; NN : Nodes_Type renames HT.Nodes; Old_Indx : Hash_Type; New_Indx : constant Hash_Type := Checked_Index (HT, Key); New_Bucket : Count_Type renames BB (New_Indx); N, M : Count_Type; begin -- Per AI05-0022, the container implementation is required to detect -- element tampering by a generic actual subprogram. -- The following block appears to be vestigial -- this should be done -- using Checked_Index instead. Also, we might have to move the actual -- tampering checks to the top of the subprogram, in order to prevent -- infinite recursion when calling Hash. (This is similar to how Insert -- and Delete are implemented.) This implies that we will have to defer -- the computation of New_Index until after the tampering check. ??? declare B : Natural renames HT.Busy; L : Natural renames HT.Lock; begin B := B + 1; L := L + 1; Old_Indx := HT.Buckets'First + Hash (NN (Node)) mod HT.Buckets'Length; B := B - 1; L := L - 1; exception when others => B := B - 1; L := L - 1; raise; end; -- Replace_Element is allowed to change a node's key to Key -- (generic formal operation Assign provides the mechanism), but -- only if Key is not already in the hash table. (In a unique-key -- hash table as this one, a key is mapped to exactly one node.) if Checked_Equivalent_Keys (HT, Key, Node) then if HT.Lock > 0 then raise Program_Error with "attempt to tamper with elements (container is locked)"; end if; -- The new Key value is mapped to this same Node, so Node -- stays in the same bucket. Assign (NN (Node), Key); return; end if; -- Key is not equivalent to Node, so we now have to determine if it's -- equivalent to some other node in the hash table. This is the case -- irrespective of whether Key is in the same or a different bucket from -- Node. N := New_Bucket; while N /= 0 loop if Checked_Equivalent_Keys (HT, Key, N) then pragma Assert (N /= Node); raise Program_Error with "attempt to replace existing element"; end if; N := Next (NN (N)); end loop; -- We have determined that Key is not already in the hash table, so -- the change is tentatively allowed. We now perform the standard -- checks to determine whether the hash table is locked (because you -- cannot change an element while it's in use by Query_Element or -- Update_Element), or if the container is busy (because moving a -- node to a different bucket would interfere with iteration). if Old_Indx = New_Indx then -- The node is already in the bucket implied by Key. In this case -- we merely change its value without moving it. if HT.Lock > 0 then raise Program_Error with "attempt to tamper with elements (container is locked)"; end if; Assign (NN (Node), Key); return; end if; -- The node is a bucket different from the bucket implied by Key if HT.Busy > 0 then raise Program_Error with "attempt to tamper with cursors (container is busy)"; end if; -- Do the assignment first, before moving the node, so that if Assign -- propagates an exception, then the hash table will not have been -- modified (except for any possible side-effect Assign had on Node). Assign (NN (Node), Key); -- Now we can safely remove the node from its current bucket N := BB (Old_Indx); -- get value of first node in old bucket pragma Assert (N /= 0); if N = Node then -- node is first node in its bucket BB (Old_Indx) := Next (NN (Node)); else pragma Assert (HT.Length > 1); loop M := Next (NN (N)); pragma Assert (M /= 0); if M = Node then Set_Next (NN (N), Next => Next (NN (Node))); exit; end if; N := M; end loop; end if; -- Now we link the node into its new bucket (corresponding to Key) Set_Next (NN (Node), Next => New_Bucket); New_Bucket := Node; end Generic_Replace_Element; ----------- -- Index -- ----------- function Index (HT : Hash_Table_Type'Class; Key : Key_Type) return Hash_Type is begin return HT.Buckets'First + Hash (Key) mod HT.Buckets'Length; end Index; end Ada.Containers.Hash_Tables.Generic_Bounded_Keys;