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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- G N A T . D Y N A M I C _ H T A B L E S --
-- --
-- B o d y --
-- --
-- Copyright (C) 2002-2022, AdaCore --
-- --
-- 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/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Ada.Unchecked_Deallocation;
package body GNAT.Dynamic_HTables is
-------------------
-- Hash_Two_Keys --
-------------------
function Hash_Two_Keys
(Left : Bucket_Range_Type;
Right : Bucket_Range_Type) return Bucket_Range_Type
is
Half : constant := 2 ** (Bucket_Range_Type'Size / 2);
Mask : constant := Half - 1;
begin
-- The hash is obtained in the following manner:
--
-- 1) The low bits of Left are obtained, then shifted over to the high
-- bits position.
--
-- 2) The low bits of Right are obtained
--
-- The results from 1) and 2) are or-ed to produce a value within the
-- range of Bucket_Range_Type.
return
((Left and Mask) * Half)
or
(Right and Mask);
end Hash_Two_Keys;
-------------------
-- Static_HTable --
-------------------
package body Static_HTable is
function Get_Non_Null (T : Instance) return Elmt_Ptr;
-- Returns Null_Ptr if Iterator_Started is False or if the Table is
-- empty. Returns Iterator_Ptr if non null, or the next non null element
-- in table if any.
---------
-- Get --
---------
function Get (T : Instance; K : Key) return Elmt_Ptr is
Elmt : Elmt_Ptr;
begin
if T = null then
return Null_Ptr;
end if;
Elmt := T.Table (Hash (K));
loop
if Elmt = Null_Ptr then
return Null_Ptr;
elsif Equal (Get_Key (Elmt), K) then
return Elmt;
else
Elmt := Next (Elmt);
end if;
end loop;
end Get;
---------------
-- Get_First --
---------------
function Get_First (T : Instance) return Elmt_Ptr is
begin
if T = null then
return Null_Ptr;
end if;
T.Iterator_Started := True;
T.Iterator_Index := T.Table'First;
T.Iterator_Ptr := T.Table (T.Iterator_Index);
return Get_Non_Null (T);
end Get_First;
--------------
-- Get_Next --
--------------
function Get_Next (T : Instance) return Elmt_Ptr is
begin
if T = null or else not T.Iterator_Started then
return Null_Ptr;
end if;
T.Iterator_Ptr := Next (T.Iterator_Ptr);
return Get_Non_Null (T);
end Get_Next;
------------------
-- Get_Non_Null --
------------------
function Get_Non_Null (T : Instance) return Elmt_Ptr is
begin
if T = null then
return Null_Ptr;
end if;
while T.Iterator_Ptr = Null_Ptr loop
if T.Iterator_Index = T.Table'Last then
T.Iterator_Started := False;
return Null_Ptr;
end if;
T.Iterator_Index := T.Iterator_Index + 1;
T.Iterator_Ptr := T.Table (T.Iterator_Index);
end loop;
return T.Iterator_Ptr;
end Get_Non_Null;
------------
-- Remove --
------------
procedure Remove (T : Instance; K : Key) is
Index : constant Header_Num := Hash (K);
Elmt : Elmt_Ptr;
Next_Elmt : Elmt_Ptr;
begin
if T = null then
return;
end if;
Elmt := T.Table (Index);
if Elmt = Null_Ptr then
return;
elsif Equal (Get_Key (Elmt), K) then
T.Table (Index) := Next (Elmt);
else
loop
Next_Elmt := Next (Elmt);
if Next_Elmt = Null_Ptr then
return;
elsif Equal (Get_Key (Next_Elmt), K) then
Set_Next (Elmt, Next (Next_Elmt));
return;
else
Elmt := Next_Elmt;
end if;
end loop;
end if;
end Remove;
-----------
-- Reset --
-----------
procedure Reset (T : in out Instance) is
procedure Free is
new Ada.Unchecked_Deallocation (Instance_Data, Instance);
begin
if T = null then
return;
end if;
for J in T.Table'Range loop
T.Table (J) := Null_Ptr;
end loop;
Free (T);
end Reset;
---------
-- Set --
---------
procedure Set (T : in out Instance; E : Elmt_Ptr) is
Index : Header_Num;
begin
if T = null then
T := new Instance_Data;
end if;
Index := Hash (Get_Key (E));
Set_Next (E, T.Table (Index));
T.Table (Index) := E;
end Set;
end Static_HTable;
-------------------
-- Simple_HTable --
-------------------
package body Simple_HTable is
procedure Free is new
Ada.Unchecked_Deallocation (Element_Wrapper, Elmt_Ptr);
---------
-- Get --
---------
function Get (T : Instance; K : Key) return Element is
Tmp : Elmt_Ptr;
begin
if T = Nil then
return No_Element;
end if;
Tmp := Tab.Get (Tab.Instance (T), K);
if Tmp = null then
return No_Element;
else
return Tmp.E;
end if;
end Get;
---------------
-- Get_First --
---------------
function Get_First (T : Instance) return Element is
Tmp : constant Elmt_Ptr := Tab.Get_First (Tab.Instance (T));
begin
if Tmp = null then
return No_Element;
else
return Tmp.E;
end if;
end Get_First;
-------------------
-- Get_First_Key --
-------------------
function Get_First_Key (T : Instance) return Key_Option is
Tmp : constant Elmt_Ptr := Tab.Get_First (Tab.Instance (T));
begin
if Tmp = null then
return Key_Option'(Present => False);
else
return Key_Option'(Present => True, K => Tmp.all.K);
end if;
end Get_First_Key;
-------------
-- Get_Key --
-------------
function Get_Key (E : Elmt_Ptr) return Key is
begin
return E.K;
end Get_Key;
--------------
-- Get_Next --
--------------
function Get_Next (T : Instance) return Element is
Tmp : constant Elmt_Ptr := Tab.Get_Next (Tab.Instance (T));
begin
if Tmp = null then
return No_Element;
else
return Tmp.E;
end if;
end Get_Next;
------------------
-- Get_Next_Key --
------------------
function Get_Next_Key (T : Instance) return Key_Option is
Tmp : constant Elmt_Ptr := Tab.Get_Next (Tab.Instance (T));
begin
if Tmp = null then
return Key_Option'(Present => False);
else
return Key_Option'(Present => True, K => Tmp.all.K);
end if;
end Get_Next_Key;
----------
-- Next --
----------
function Next (E : Elmt_Ptr) return Elmt_Ptr is
begin
return E.Next;
end Next;
------------
-- Remove --
------------
procedure Remove (T : Instance; K : Key) is
Tmp : Elmt_Ptr;
begin
Tmp := Tab.Get (Tab.Instance (T), K);
if Tmp /= null then
Tab.Remove (Tab.Instance (T), K);
Free (Tmp);
end if;
end Remove;
-----------
-- Reset --
-----------
procedure Reset (T : in out Instance) is
E1, E2 : Elmt_Ptr;
begin
E1 := Tab.Get_First (Tab.Instance (T));
while E1 /= null loop
E2 := Tab.Get_Next (Tab.Instance (T));
Free (E1);
E1 := E2;
end loop;
Tab.Reset (Tab.Instance (T));
end Reset;
---------
-- Set --
---------
procedure Set (T : in out Instance; K : Key; E : Element) is
Tmp : constant Elmt_Ptr := Tab.Get (Tab.Instance (T), K);
begin
if Tmp = null then
Tab.Set (Tab.Instance (T), new Element_Wrapper'(K, E, null));
else
Tmp.E := E;
end if;
end Set;
--------------
-- Set_Next --
--------------
procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr) is
begin
E.Next := Next;
end Set_Next;
end Simple_HTable;
-------------------------
-- Dynamic_Hash_Tables --
-------------------------
package body Dynamic_Hash_Tables is
Minimum_Size : constant Bucket_Range_Type := 8;
-- Minimum size of the buckets
Safe_Compression_Size : constant Bucket_Range_Type :=
Minimum_Size * Compression_Factor;
-- Maximum safe size for hash table compression. Beyond this size, a
-- compression will violate the minimum size constraint on the buckets.
Safe_Expansion_Size : constant Bucket_Range_Type :=
Bucket_Range_Type'Last / Expansion_Factor;
-- Maximum safe size for hash table expansion. Beyond this size, an
-- expansion will overflow the buckets.
procedure Delete_Node
(T : Dynamic_Hash_Table;
Nod : Node_Ptr);
pragma Inline (Delete_Node);
-- Detach and delete node Nod from table T
procedure Destroy_Buckets (Bkts : Bucket_Table_Ptr);
pragma Inline (Destroy_Buckets);
-- Destroy all nodes within buckets Bkts
procedure Detach (Nod : Node_Ptr);
pragma Inline (Detach);
-- Detach node Nod from the bucket it resides in
procedure Ensure_Circular (Head : Node_Ptr);
pragma Inline (Ensure_Circular);
-- Ensure that dummy head Head is circular with respect to itself
procedure Ensure_Created (T : Dynamic_Hash_Table);
pragma Inline (Ensure_Created);
-- Verify that hash table T is created. Raise Not_Created if this is not
-- the case.
procedure Ensure_Unlocked (T : Dynamic_Hash_Table);
pragma Inline (Ensure_Unlocked);
-- Verify that hash table T is unlocked. Raise Iterated if this is not
-- the case.
function Find_Bucket
(Bkts : Bucket_Table_Ptr;
Key : Key_Type) return Node_Ptr;
pragma Inline (Find_Bucket);
-- Find the bucket among buckets Bkts which corresponds to key Key, and
-- return its dummy head.
function Find_Node (Head : Node_Ptr; Key : Key_Type) return Node_Ptr;
pragma Inline (Find_Node);
-- Traverse a bucket indicated by dummy head Head to determine whether
-- there exists a node with key Key. If such a node exists, return it,
-- otherwise return null.
procedure First_Valid_Node
(T : Dynamic_Hash_Table;
Low_Bkt : Bucket_Range_Type;
High_Bkt : Bucket_Range_Type;
Idx : out Bucket_Range_Type;
Nod : out Node_Ptr);
pragma Inline (First_Valid_Node);
-- Find the first valid node in the buckets of hash table T constrained
-- by the range Low_Bkt .. High_Bkt. If such a node exists, return its
-- bucket index in Idx and reference in Nod. If no such node exists,
-- Idx is set to 0 and Nod to null.
procedure Free is
new Ada.Unchecked_Deallocation (Bucket_Table, Bucket_Table_Ptr);
procedure Free is
new Ada.Unchecked_Deallocation
(Dynamic_Hash_Table_Attributes, Dynamic_Hash_Table);
procedure Free is
new Ada.Unchecked_Deallocation (Node, Node_Ptr);
function Is_Valid (Iter : Iterator) return Boolean;
pragma Inline (Is_Valid);
-- Determine whether iterator Iter refers to a valid key-value pair
function Is_Valid (Nod : Node_Ptr; Head : Node_Ptr) return Boolean;
pragma Inline (Is_Valid);
-- Determine whether node Nod is non-null and does not refer to dummy
-- head Head, thus making it valid.
function Load_Factor (T : Dynamic_Hash_Table) return Threshold_Type;
pragma Inline (Load_Factor);
-- Calculate the load factor of hash table T
procedure Lock (T : Dynamic_Hash_Table);
pragma Inline (Lock);
-- Lock all mutation functionality of hash table T
procedure Mutate_And_Rehash
(T : Dynamic_Hash_Table;
Size : Bucket_Range_Type);
pragma Inline (Mutate_And_Rehash);
-- Replace the buckets of hash table T with a new set of buckets of size
-- Size. Rehash all key-value pairs from the old to the new buckets.
procedure Prepend (Nod : Node_Ptr; Head : Node_Ptr);
pragma Inline (Prepend);
-- Insert node Nod immediately after dummy head Head
function Present (Bkts : Bucket_Table_Ptr) return Boolean;
pragma Inline (Present);
-- Determine whether buckets Bkts exist
function Present (Nod : Node_Ptr) return Boolean;
pragma Inline (Present);
-- Determine whether node Nod exists
procedure Unlock (T : Dynamic_Hash_Table);
pragma Inline (Unlock);
-- Unlock all mutation functionality of hash table T
--------------
-- Contains --
--------------
function Contains
(T : Dynamic_Hash_Table;
Key : Key_Type) return Boolean
is
Head : Node_Ptr;
Nod : Node_Ptr;
begin
Ensure_Created (T);
-- Obtain the dummy head of the bucket which should house the
-- key-value pair.
Head := Find_Bucket (T.Buckets, Key);
-- Try to find a node in the bucket which matches the key
Nod := Find_Node (Head, Key);
return Is_Valid (Nod, Head);
end Contains;
------------
-- Create --
------------
function Create (Initial_Size : Positive) return Dynamic_Hash_Table is
Size : constant Bucket_Range_Type :=
Bucket_Range_Type'Max
(Bucket_Range_Type (Initial_Size), Minimum_Size);
-- Ensure that the buckets meet a minimum size
T : constant Dynamic_Hash_Table := new Dynamic_Hash_Table_Attributes;
begin
T.Buckets := new Bucket_Table (0 .. Size - 1);
T.Initial_Size := Size;
return T;
end Create;
------------
-- Delete --
------------
procedure Delete
(T : Dynamic_Hash_Table;
Key : Key_Type)
is
Head : Node_Ptr;
Nod : Node_Ptr;
begin
Ensure_Created (T);
Ensure_Unlocked (T);
-- Obtain the dummy head of the bucket which should house the
-- key-value pair.
Head := Find_Bucket (T.Buckets, Key);
-- Try to find a node in the bucket which matches the key
Nod := Find_Node (Head, Key);
-- If such a node exists, remove it from the bucket and deallocate it
if Is_Valid (Nod, Head) then
Delete_Node (T, Nod);
end if;
end Delete;
-----------------
-- Delete_Node --
-----------------
procedure Delete_Node
(T : Dynamic_Hash_Table;
Nod : Node_Ptr)
is
procedure Compress;
pragma Inline (Compress);
-- Determine whether hash table T requires compression, and if so,
-- half its size.
--------------
-- Compress --
--------------
procedure Compress is
pragma Assert (Present (T));
pragma Assert (Present (T.Buckets));
Old_Size : constant Bucket_Range_Type := T.Buckets'Length;
begin
-- The ratio of pairs to buckets is under the desited threshold.
-- Compress the hash table only when there is still room to do so.
if Load_Factor (T) < Compression_Threshold
and then Old_Size >= Safe_Compression_Size
then
Mutate_And_Rehash (T, Old_Size / Compression_Factor);
end if;
end Compress;
-- Local variables
Ref : Node_Ptr := Nod;
-- Start of processing for Delete_Node
begin
pragma Assert (Present (Ref));
pragma Assert (Present (T));
Detach (Ref);
Free (Ref);
-- The number of key-value pairs is updated when the hash table
-- contains a valid node which represents the pair.
T.Pairs := T.Pairs - 1;
-- Compress the hash table if the load factor drops below the value
-- of Compression_Threshold.
Compress;
end Delete_Node;
-------------
-- Destroy --
-------------
procedure Destroy (T : in out Dynamic_Hash_Table) is
begin
Ensure_Created (T);
Ensure_Unlocked (T);
-- Destroy all nodes in all buckets
Destroy_Buckets (T.Buckets);
Free (T.Buckets);
Free (T);
end Destroy;
---------------------
-- Destroy_Buckets --
---------------------
procedure Destroy_Buckets (Bkts : Bucket_Table_Ptr) is
procedure Destroy_Bucket (Head : Node_Ptr);
pragma Inline (Destroy_Bucket);
-- Destroy all nodes in a bucket with dummy head Head
--------------------
-- Destroy_Bucket --
--------------------
procedure Destroy_Bucket (Head : Node_Ptr) is
Nod : Node_Ptr;
begin
-- Destroy all valid nodes which follow the dummy head
while Is_Valid (Head.Next, Head) loop
Nod := Head.Next;
-- Invoke the value destructor before deallocating the node
Destroy_Value (Nod.Value);
Detach (Nod);
Free (Nod);
end loop;
end Destroy_Bucket;
-- Start of processing for Destroy_Buckets
begin
pragma Assert (Present (Bkts));
for Scan_Idx in Bkts'Range loop
Destroy_Bucket (Bkts (Scan_Idx)'Access);
end loop;
end Destroy_Buckets;
------------
-- Detach --
------------
procedure Detach (Nod : Node_Ptr) is
pragma Assert (Present (Nod));
Next : constant Node_Ptr := Nod.Next;
Prev : constant Node_Ptr := Nod.Prev;
begin
pragma Assert (Present (Next));
pragma Assert (Present (Prev));
Prev.Next := Next; -- Prev ---> Next
Next.Prev := Prev; -- Prev <--> Next
Nod.Next := null;
Nod.Prev := null;
end Detach;
---------------------
-- Ensure_Circular --
---------------------
procedure Ensure_Circular (Head : Node_Ptr) is
pragma Assert (Present (Head));
begin
if not Present (Head.Next) and then not Present (Head.Prev) then
Head.Next := Head;
Head.Prev := Head;
end if;
end Ensure_Circular;
--------------------
-- Ensure_Created --
--------------------
procedure Ensure_Created (T : Dynamic_Hash_Table) is
begin
if not Present (T) then
raise Not_Created;
end if;
end Ensure_Created;
---------------------
-- Ensure_Unlocked --
---------------------
procedure Ensure_Unlocked (T : Dynamic_Hash_Table) is
begin
pragma Assert (Present (T));
-- The hash table has at least one outstanding iterator
if T.Iterators > 0 then
raise Iterated;
end if;
end Ensure_Unlocked;
-----------------
-- Find_Bucket --
-----------------
function Find_Bucket
(Bkts : Bucket_Table_Ptr;
Key : Key_Type) return Node_Ptr
is
pragma Assert (Present (Bkts));
Idx : constant Bucket_Range_Type := Hash (Key) mod Bkts'Length;
begin
return Bkts (Idx)'Access;
end Find_Bucket;
---------------
-- Find_Node --
---------------
function Find_Node (Head : Node_Ptr; Key : Key_Type) return Node_Ptr is
pragma Assert (Present (Head));
Nod : Node_Ptr;
begin
-- Traverse the nodes of the bucket, looking for a key-value pair
-- with the same key.
Nod := Head.Next;
while Is_Valid (Nod, Head) loop
if Nod.Key = Key then
return Nod;
end if;
Nod := Nod.Next;
end loop;
return null;
end Find_Node;
----------------------
-- First_Valid_Node --
----------------------
procedure First_Valid_Node
(T : Dynamic_Hash_Table;
Low_Bkt : Bucket_Range_Type;
High_Bkt : Bucket_Range_Type;
Idx : out Bucket_Range_Type;
Nod : out Node_Ptr)
is
Head : Node_Ptr;
begin
pragma Assert (Present (T));
pragma Assert (Present (T.Buckets));
-- Assume that no valid node exists
Idx := 0;
Nod := null;
-- Examine the buckets of the hash table within the requested range,
-- looking for the first valid node.
for Scan_Idx in Low_Bkt .. High_Bkt loop
Head := T.Buckets (Scan_Idx)'Access;
-- The bucket contains at least one valid node, return the first
-- such node.
if Is_Valid (Head.Next, Head) then
Idx := Scan_Idx;
Nod := Head.Next;
return;
end if;
end loop;
end First_Valid_Node;
---------
-- Get --
---------
function Get
(T : Dynamic_Hash_Table;
Key : Key_Type) return Value_Type
is
Head : Node_Ptr;
Nod : Node_Ptr;
begin
Ensure_Created (T);
-- Obtain the dummy head of the bucket which should house the
-- key-value pair.
Head := Find_Bucket (T.Buckets, Key);
-- Try to find a node in the bucket which matches the key
Nod := Find_Node (Head, Key);
-- If such a node exists, return the value of the key-value pair
if Is_Valid (Nod, Head) then
return Nod.Value;
end if;
return No_Value;
end Get;
--------------
-- Has_Next --
--------------
function Has_Next (Iter : Iterator) return Boolean is
Is_OK : constant Boolean := Is_Valid (Iter);
T : constant Dynamic_Hash_Table := Iter.Table;
begin
pragma Assert (Present (T));
-- The iterator is no longer valid which indicates that it has been
-- exhausted. Unlock all mutation functionality of the hash table
-- because the iterator cannot be advanced any further.
if not Is_OK then
Unlock (T);
end if;
return Is_OK;
end Has_Next;
--------------
-- Is_Empty --
--------------
function Is_Empty (T : Dynamic_Hash_Table) return Boolean is
begin
Ensure_Created (T);
return T.Pairs = 0;
end Is_Empty;
--------------
-- Is_Valid --
--------------
function Is_Valid (Iter : Iterator) return Boolean is
begin
-- The invariant of Iterate and Next ensures that the iterator always
-- refers to a valid node if there exists one.
return Present (Iter.Curr_Nod);
end Is_Valid;
--------------
-- Is_Valid --
--------------
function Is_Valid (Nod : Node_Ptr; Head : Node_Ptr) return Boolean is
begin
-- A node is valid if it is non-null, and does not refer to the dummy
-- head of some bucket.
return Present (Nod) and then Nod /= Head;
end Is_Valid;
-------------
-- Iterate --
-------------
function Iterate (T : Dynamic_Hash_Table) return Iterator is
Iter : Iterator;
begin
Ensure_Created (T);
pragma Assert (Present (T.Buckets));
-- Initialize the iterator to reference the first valid node in
-- the full range of hash table buckets. If no such node exists,
-- the iterator is left in a state which does not allow it to
-- advance.
First_Valid_Node
(T => T,
Low_Bkt => T.Buckets'First,
High_Bkt => T.Buckets'Last,
Idx => Iter.Curr_Idx,
Nod => Iter.Curr_Nod);
-- Associate the iterator with the hash table to allow for future
-- mutation functionality unlocking.
Iter.Table := T;
-- Lock all mutation functionality of the hash table while it is
-- being iterated on.
Lock (T);
return Iter;
end Iterate;
-----------------
-- Load_Factor --
-----------------
function Load_Factor (T : Dynamic_Hash_Table) return Threshold_Type is
pragma Assert (Present (T));
pragma Assert (Present (T.Buckets));
begin
-- The load factor is the ratio of key-value pairs to buckets
return Threshold_Type (T.Pairs) / Threshold_Type (T.Buckets'Length);
end Load_Factor;
----------
-- Lock --
----------
procedure Lock (T : Dynamic_Hash_Table) is
begin
-- The hash table may be locked multiple times if multiple iterators
-- are operating over it.
T.Iterators := T.Iterators + 1;
end Lock;
-----------------------
-- Mutate_And_Rehash --
-----------------------
procedure Mutate_And_Rehash
(T : Dynamic_Hash_Table;
Size : Bucket_Range_Type)
is
procedure Rehash (From : Bucket_Table_Ptr; To : Bucket_Table_Ptr);
pragma Inline (Rehash);
-- Remove all nodes from buckets From and rehash them into buckets To
procedure Rehash_Bucket (Head : Node_Ptr; To : Bucket_Table_Ptr);
pragma Inline (Rehash_Bucket);
-- Detach all nodes starting from dummy head Head and rehash them
-- into To.
procedure Rehash_Node (Nod : Node_Ptr; To : Bucket_Table_Ptr);
pragma Inline (Rehash_Node);
-- Rehash node Nod into To
------------
-- Rehash --
------------
procedure Rehash (From : Bucket_Table_Ptr; To : Bucket_Table_Ptr) is
begin
pragma Assert (Present (From));
pragma Assert (Present (To));
for Scan_Idx in From'Range loop
Rehash_Bucket (From (Scan_Idx)'Access, To);
end loop;
end Rehash;
-------------------
-- Rehash_Bucket --
-------------------
procedure Rehash_Bucket (Head : Node_Ptr; To : Bucket_Table_Ptr) is
pragma Assert (Present (Head));
Nod : Node_Ptr;
begin
-- Detach all nodes which follow the dummy head
while Is_Valid (Head.Next, Head) loop
Nod := Head.Next;
Detach (Nod);
Rehash_Node (Nod, To);
end loop;
end Rehash_Bucket;
-----------------
-- Rehash_Node --
-----------------
procedure Rehash_Node (Nod : Node_Ptr; To : Bucket_Table_Ptr) is
pragma Assert (Present (Nod));
Head : Node_Ptr;
begin
-- Obtain the dummy head of the bucket which should house the
-- key-value pair.
Head := Find_Bucket (To, Nod.Key);
-- Ensure that the dummy head of an empty bucket is circular with
-- respect to itself.
Ensure_Circular (Head);
-- Prepend the node to the bucket
Prepend (Nod, Head);
end Rehash_Node;
-- Local declarations
Old_Bkts : Bucket_Table_Ptr;
-- Start of processing for Mutate_And_Rehash
begin
pragma Assert (Present (T));
Old_Bkts := T.Buckets;
T.Buckets := new Bucket_Table (0 .. Size - 1);
-- Transfer and rehash all key-value pairs from the old buckets to
-- the new buckets.
Rehash (From => Old_Bkts, To => T.Buckets);
Free (Old_Bkts);
end Mutate_And_Rehash;
----------
-- Next --
----------
procedure Next (Iter : in out Iterator; Key : out Key_Type) is
Is_OK : constant Boolean := Is_Valid (Iter);
Saved : constant Node_Ptr := Iter.Curr_Nod;
T : constant Dynamic_Hash_Table := Iter.Table;
Head : Node_Ptr;
begin
pragma Assert (Present (T));
pragma Assert (Present (T.Buckets));
-- The iterator is no longer valid which indicates that it has been
-- exhausted. Unlock all mutation functionality of the hash table as
-- the iterator cannot be advanced any further.
if not Is_OK then
Unlock (T);
raise Iterator_Exhausted;
end if;
-- Advance to the next node along the same bucket
Iter.Curr_Nod := Iter.Curr_Nod.Next;
Head := T.Buckets (Iter.Curr_Idx)'Access;
-- If the new node is no longer valid, then this indicates that the
-- current bucket has been exhausted. Advance to the next valid node
-- within the remaining range of buckets. If no such node exists, the
-- iterator is left in a state which does not allow it to advance.
if not Is_Valid (Iter.Curr_Nod, Head) then
First_Valid_Node
(T => T,
Low_Bkt => Iter.Curr_Idx + 1,
High_Bkt => T.Buckets'Last,
Idx => Iter.Curr_Idx,
Nod => Iter.Curr_Nod);
end if;
Key := Saved.Key;
end Next;
-------------
-- Prepend --
-------------
procedure Prepend (Nod : Node_Ptr; Head : Node_Ptr) is
pragma Assert (Present (Nod));
pragma Assert (Present (Head));
Next : constant Node_Ptr := Head.Next;
begin
Head.Next := Nod;
Next.Prev := Nod;
Nod.Next := Next;
Nod.Prev := Head;
end Prepend;
-------------
-- Present --
-------------
function Present (Bkts : Bucket_Table_Ptr) return Boolean is
begin
return Bkts /= null;
end Present;
-------------
-- Present --
-------------
function Present (Nod : Node_Ptr) return Boolean is
begin
return Nod /= null;
end Present;
-------------
-- Present --
-------------
function Present (T : Dynamic_Hash_Table) return Boolean is
begin
return T /= Nil;
end Present;
---------
-- Put --
---------
procedure Put
(T : Dynamic_Hash_Table;
Key : Key_Type;
Value : Value_Type)
is
procedure Expand;
pragma Inline (Expand);
-- Determine whether hash table T requires expansion, and if so,
-- double its size.
procedure Prepend_Or_Replace (Head : Node_Ptr);
pragma Inline (Prepend_Or_Replace);
-- Update the value of a node within a bucket with dummy head Head
-- whose key is Key to Value. If there is no such node, prepend a new
-- key-value pair to the bucket.
------------
-- Expand --
------------
procedure Expand is
pragma Assert (Present (T));
pragma Assert (Present (T.Buckets));
Old_Size : constant Bucket_Range_Type := T.Buckets'Length;
begin
-- The ratio of pairs to buckets is over the desited threshold.
-- Expand the hash table only when there is still room to do so.
if Load_Factor (T) > Expansion_Threshold
and then Old_Size <= Safe_Expansion_Size
then
Mutate_And_Rehash (T, Old_Size * Expansion_Factor);
end if;
end Expand;
------------------------
-- Prepend_Or_Replace --
------------------------
procedure Prepend_Or_Replace (Head : Node_Ptr) is
pragma Assert (Present (Head));
Nod : Node_Ptr;
begin
-- If the bucket containst at least one valid node, then there is
-- a chance that a node with the same key as Key exists. If this
-- is the case, the value of that node must be updated.
Nod := Head.Next;
while Is_Valid (Nod, Head) loop
if Nod.Key = Key then
Nod.Value := Value;
return;
end if;
Nod := Nod.Next;
end loop;
-- At this point the bucket is either empty, or none of the nodes
-- match key Key. Prepend a new key-value pair.
Nod := new Node'(Key, Value, null, null);
Prepend (Nod, Head);
-- The number of key-value pairs must be updated for a prepend,
-- never for a replace.
T.Pairs := T.Pairs + 1;
end Prepend_Or_Replace;
-- Local variables
Head : Node_Ptr;
-- Start of processing for Put
begin
Ensure_Created (T);
Ensure_Unlocked (T);
-- Obtain the dummy head of the bucket which should house the
-- key-value pair.
Head := Find_Bucket (T.Buckets, Key);
-- Ensure that the dummy head of an empty bucket is circular with
-- respect to itself.
Ensure_Circular (Head);
-- In case the bucket already contains a node with the same key,
-- replace its value, otherwise prepend a new key-value pair.
Prepend_Or_Replace (Head);
-- Expand the hash table if the ratio of pairs to buckets goes over
-- Expansion_Threshold.
Expand;
end Put;
-----------
-- Reset --
-----------
procedure Reset (T : Dynamic_Hash_Table) is
begin
Ensure_Created (T);
Ensure_Unlocked (T);
-- Destroy all nodes in all buckets
Destroy_Buckets (T.Buckets);
Free (T.Buckets);
-- Recreate the buckets using the original size from creation time
T.Buckets := new Bucket_Table (0 .. T.Initial_Size - 1);
T.Pairs := 0;
end Reset;
----------
-- Size --
----------
function Size (T : Dynamic_Hash_Table) return Natural is
begin
Ensure_Created (T);
return T.Pairs;
end Size;
------------
-- Unlock --
------------
procedure Unlock (T : Dynamic_Hash_Table) is
begin
-- The hash table may be locked multiple times if multiple iterators
-- are operating over it.
T.Iterators := T.Iterators - 1;
end Unlock;
end Dynamic_Hash_Tables;
end GNAT.Dynamic_HTables;