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------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- ADA.CONTAINERS.HASH_TABLES.GENERIC_KEYS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2004-2007, 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 2, 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- 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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