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------------------------------------------------------------------------------ -- -- -- GNAT LIBRARY COMPONENTS -- -- -- -- ADA.CONTAINERS.HASH_TABLES.GENERIC_KEYS -- -- -- -- B o d y -- -- -- -- Copyright (C) 2004-2009, 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 -- -- <http://www.gnu.org/licenses/>. -- -- -- -- This unit was originally developed by Matthew J Heaney. -- ------------------------------------------------------------------------------ package body Ada.Containers.Hash_Tables.Generic_Keys is -------------------------- -- Delete_Key_Sans_Free -- -------------------------- procedure Delete_Key_Sans_Free (HT : in out Hash_Table_Type; Key : Key_Type; X : out Node_Access) is Indx : Hash_Type; Prev : Node_Access; begin if HT.Length = 0 then X := null; return; end if; Indx := Index (HT, Key); X := HT.Buckets (Indx); if X = null then return; end if; if Equivalent_Keys (Key, X) then if HT.Busy > 0 then raise Program_Error with "attempt to tamper with elements (container is busy)"; end if; HT.Buckets (Indx) := Next (X); HT.Length := HT.Length - 1; return; end if; loop Prev := X; X := Next (Prev); if X = null then return; end if; if Equivalent_Keys (Key, X) then if HT.Busy > 0 then raise Program_Error with "attempt to tamper with elements (container is busy)"; end if; Set_Next (Node => Prev, Next => Next (X)); HT.Length := HT.Length - 1; return; end if; end loop; end Delete_Key_Sans_Free; ---------- -- Find -- ---------- function Find (HT : Hash_Table_Type; Key : Key_Type) return Node_Access is Indx : Hash_Type; Node : Node_Access; begin if HT.Length = 0 then return null; end if; Indx := Index (HT, Key); Node := HT.Buckets (Indx); while Node /= null loop if Equivalent_Keys (Key, Node) then return Node; end if; Node := Next (Node); end loop; return null; end Find; -------------------------------- -- Generic_Conditional_Insert -- -------------------------------- procedure Generic_Conditional_Insert (HT : in out Hash_Table_Type; Key : Key_Type; Node : out Node_Access; Inserted : out Boolean) is Indx : constant Hash_Type := Index (HT, Key); B : Node_Access renames HT.Buckets (Indx); begin if B = null then if HT.Busy > 0 then raise Program_Error with "attempt to tamper with elements (container is busy)"; end if; if HT.Length = Count_Type'Last then raise Constraint_Error; end if; Node := New_Node (Next => null); Inserted := True; B := Node; HT.Length := HT.Length + 1; return; end if; Node := B; loop if Equivalent_Keys (Key, Node) then Inserted := False; return; end if; Node := Next (Node); exit when Node = null; end loop; if HT.Busy > 0 then raise Program_Error with "attempt to tamper with elements (container is busy)"; end if; if HT.Length = Count_Type'Last then raise Constraint_Error; end if; Node := New_Node (Next => B); Inserted := True; B := Node; HT.Length := HT.Length + 1; end Generic_Conditional_Insert; ----------- -- Index -- ----------- function Index (HT : Hash_Table_Type; Key : Key_Type) return Hash_Type is begin return Hash (Key) mod HT.Buckets'Length; end Index; ----------------------------- -- Generic_Replace_Element -- ----------------------------- procedure Generic_Replace_Element (HT : in out Hash_Table_Type; Node : Node_Access; Key : Key_Type) is pragma Assert (HT.Length > 0); pragma Assert (Node /= null); Old_Hash : constant Hash_Type := Hash (Node); Old_Indx : constant Hash_Type := Old_Hash mod HT.Buckets'Length; New_Hash : constant Hash_Type := Hash (Key); New_Indx : constant Hash_Type := New_Hash mod HT.Buckets'Length; New_Bucket : Node_Access renames HT.Buckets (New_Indx); N, M : Node_Access; begin if Equivalent_Keys (Key, Node) then pragma Assert (New_Hash = Old_Hash); if HT.Lock > 0 then raise Program_Error with "attempt to tamper with cursors (container is locked)"; end if; -- We can change a node's key to Key (that's what Assign is for), 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 only.) -- The exception is when Key is mapped to Node, in which case the -- change is allowed. Assign (Node, Key); pragma Assert (Hash (Node) = New_Hash); pragma Assert (Equivalent_Keys (Key, Node)); 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 /= null loop if Equivalent_Keys (Key, N) then pragma Assert (N /= Node); raise Program_Error with "attempt to replace existing element"; end if; N := Next (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 cursors (container is locked)"; end if; Assign (Node, Key); pragma Assert (Hash (Node) = New_Hash); pragma Assert (Equivalent_Keys (Key, Node)); 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 elements (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 (Node, Key); pragma Assert (Hash (Node) = New_Hash); pragma Assert (Equivalent_Keys (Key, Node)); -- Now we can safely remove the node from its current bucket N := HT.Buckets (Old_Indx); pragma Assert (N /= null); if N = Node then HT.Buckets (Old_Indx) := Next (Node); else pragma Assert (HT.Length > 1); loop M := Next (N); pragma Assert (M /= null); if M = Node then Set_Next (Node => N, Next => Next (Node)); exit; end if; N := M; end loop; end if; -- Now we link the node into its new bucket (corresponding to Key) Set_Next (Node => Node, Next => New_Bucket); New_Bucket := Node; end Generic_Replace_Element; end Ada.Containers.Hash_Tables.Generic_Keys;
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