------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- ADA.CONTAINERS.HASH_TABLES.GENERIC_FORMAL_KEYS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2004-2023, 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_Formal_Keys is
Checks : constant Boolean := Container_Checks'Enabled;
--------------------------
-- Delete_Key_Sans_Free --
--------------------------
procedure Delete_Key_Sans_Free
(HT : in out Hash_Table_Type;
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;
Indx := Index (HT, Key);
X := HT.Buckets (Indx);
if X = 0 then
return;
end if;
if Equivalent_Keys (Key, HT.Nodes (X)) then
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 Equivalent_Keys (Key, HT.Nodes (X)) then
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;
Key : Key_Type) return Count_Type
is
Indx : Hash_Type;
Node : Count_Type;
begin
if HT.Length = 0 then
return 0;
end if;
Indx := Index (HT, Key);
Node := HT.Buckets (Indx);
while Node /= 0 loop
if Equivalent_Keys (Key, HT.Nodes (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;
Key : Key_Type;
Node : out Count_Type;
Inserted : out Boolean)
is
Indx : Hash_Type;
begin
Indx := Index (HT, Key);
Node := HT.Buckets (Indx);
if Node = 0 then
if Checks and then HT.Length = HT.Capacity then
raise Capacity_Error with "no more capacity for insertion";
end if;
New_Node (HT, Node);
Set_Next (HT.Nodes (Node), Next => 0);
Inserted := True;
HT.Buckets (Indx) := Node;
HT.Length := HT.Length + 1;
return;
end if;
loop
if Equivalent_Keys (Key, HT.Nodes (Node)) then
Inserted := False;
return;
end if;
Node := Next (HT.Nodes (Node));
exit when Node = 0;
end loop;
if Checks and then HT.Length = HT.Capacity then
raise Capacity_Error with "no more capacity for insertion";
end if;
New_Node (HT, 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;
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 := Index (HT, Key);
New_Bucket : Count_Type renames BB (New_Indx);
N, M : Count_Type;
begin
Old_Indx := HT.Buckets'First + Hash (NN (Node)) mod HT.Buckets'Length;
-- 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 Equivalent_Keys (Key, NN (Node)) then
-- 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 Checks and then Equivalent_Keys (Key, NN (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 allowed.
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.
Assign (NN (Node), Key);
return;
end if;
-- The node is in a bucket different from the bucket implied by Key.
-- 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;
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_Formal_Keys;