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{-----------------------------------------------------------------------------
The contents of this file are subject to the Mozilla Public License Version
1.1 (the "License"); you may not use this file except in compliance with the
License. You may obtain a copy of the License at
http://www.mozilla.org/NPL/NPL-1_1Final.html

Software distributed under the License is distributed on an "AS IS" basis,
WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
the specific language governing rights and limitations under the License.

The Original Code is: mwStringHashList.pas, released December 18, 2000.

The Initial Developer of the Original Code is Martin Waldenburg
(Martin.Waldenburg@T-Online.de).
Portions created by Martin Waldenburg are Copyright (C) 2000 Martin Waldenburg.
All Rights Reserved.

Contributor(s): ___________________.

Last Modified: 18/12/2000
Current Version: 1.1

Notes: This is a very fast Hash list for strings.
The TinyHash functions should be in most cases suffizient

Known Issues:
-----------------------------------------------------------------------------}

unit mwStringHashList;

interface

uses Classes, SysUtils;

var
mwHashTable: array[#0..#255] of Byte;
mwInsensitiveHashTable: array[#0..#255] of Byte;

type
TmwStringHash = function (const aString: String): Integer;
TmwStringHashCompare = function (const Str1: String; const Str2: String): Boolean;

TmwHashWord = class
S: String;
constructor Create(aString: String);
end;

PHashPointerList = ^THashPointerList;
THashPointerList = array[1..1] of Pointer;

TmwBaseStringHashList = class(TObject)
    FList: PHashPointerList;
    fCapacity: Integer;
protected
    function Get(Index: Integer): Pointer;
    procedure Put(Index: Integer; Item: Pointer);
    procedure SetCapacity(NewCapacity: Integer);
public
    destructor Destroy; override;
    property Capacity: Integer read fCapacity;
    property Items[Index: Integer]: Pointer read Get write Put; default;
end;

TmwHashStrings = class(TList)
public
destructor Destroy; override;
procedure AddString(S: String);
end;

TmwHashItems = class(TmwBaseStringHashList)
public
procedure AddString(S: String);
end;

TmwStringHashList = class(TmwBaseStringHashList)
private
    fHash: TmwStringHash;
    fCompare: TmwStringHashCompare;
public
    constructor Create(aHash: TmwStringHash; aCompare: TmwStringHashCompare);
    procedure AddString(S: String);
    function Hash(S: String): Boolean;
    function HashEX(S: String; HashValue: Integer): Boolean;
end;

function SimpleHash(const aString: String): Integer;
function ISimpleHash(const aString: String): Integer;
function TinyHash(const aString: String): Integer;
function ITinyHash(const aString: String): Integer;
function HashCompare(const Str1: String; const Str2: String): Boolean;
function IHashCompare(const Str1: String; const Str2: String): Boolean;

implementation

procedure InitTables;
var
I: Char;
begin
for I:= #0 to #255 do
begin
mwHashTable[I]:= Ord(I);
mwInsensitiveHashTable[I]:= Ord(UpperCase(String(I))[1]);
end;
end;

function SimpleHash(const aString: String): Integer;
var
I: Integer;
begin
Result:= Length(aString);
for I:= 1 to Length(aString) do
inc(Result, mwHashTable[aString[I]]);
end;

function ISimpleHash(const aString: String): Integer;
var
I: Integer;
begin
Result:= Length(aString);
for I:= 1 to Length(aString) do
inc(Result, mwInsensitiveHashTable[aString[I]]);
end;

function TinyHash(const aString: String): Integer;
var
I: Integer;
begin
Result:= Length(aString);
for I:= 1 to Length(aString) do
begin
inc(Result, mwHashTable[aString[I]]);
if I = 2 then Break;
end;
end;

function ITinyHash(const aString: String): Integer;
var
I: Integer;
begin
Result:= Length(aString);
for I:= 1 to Length(aString) do
begin
inc(Result, mwInsensitiveHashTable[aString[I]]);
if I = 2 then Break;
end;
end;

function HashCompare(const Str1: String; const Str2: String): Boolean;
var
I: Integer;
begin
if Length(Str1) <> Length(Str2) then
begin
    Result:= False;
    Exit;
end;
Result:= True;
for I:= 1 to Length(Str1) do
if Str1[I] <> Str2[I] then
begin
    Result:= False;
    Exit;
end;
end;

function IHashCompare(const Str1: String; const Str2: String): Boolean;
var
I: Integer;
begin
if Length(Str1) <> Length(Str2) then
begin
    Result:= False;
    Exit;
end;
Result:= True;
for I:= 1 to Length(Str1) do
if mwInsensitiveHashTable[Str1[I]] <> mwInsensitiveHashTable[Str2[I]] then
begin
    Result:= False;
    Exit;
end;
end;

{ TmwHashString }

constructor TmwHashWord.Create(aString: String);
begin
inherited Create;
S:= aString;
end;

{ TmwBaseStringHashList }

destructor TmwBaseStringHashList.Destroy;
var
I: Integer;
begin
for I:= 1 to fCapacity do
if Items[I] <> nil then TObject(Items[I]).Free;
ReallocMem(FList, 0);
inherited Destroy;
end;

function TmwBaseStringHashList.Get(Index: Integer): Pointer;
begin
Result:= nil;
if (Index > 0) and (Index <= fCapacity) then
Result:= fList[Index];
end;

procedure TmwBaseStringHashList.Put(Index: Integer; Item: Pointer);
begin
if (Index > 0) and (Index <= fCapacity) then
fList[Index]:= Item;
end;

procedure TmwBaseStringHashList.SetCapacity(NewCapacity: Integer);
var
I, OldCapacity: Integer;
begin
if NewCapacity > fCapacity then
begin
    ReallocMem(FList, (NewCapacity) * SizeOf(Pointer));
    OldCapacity:= fCapacity;
    FCapacity := NewCapacity;
    for I:= OldCapacity+1 to NewCapacity do Items[I]:= nil;
end;
end;

{ TmwHashStrings }

procedure TmwHashStrings.AddString(S: String);
begin
Add(TmwHashWord.Create(S));
end;

destructor TmwHashStrings.Destroy;
var
I: Integer;
begin
for I:= 0 to Count - 1 do
if Items[I] <> nil then TObject(Items[I]).Free;
inherited Destroy;
end;

{ TmwHashItems }

procedure TmwHashItems.AddString(S: String);
var
HashWord: TmwHashWord;
HashStrings: TmwHashStrings;
begin
SetCapacity(Length(S));
if Items[Length(S)] = nil then
begin
    Items[Length(S)]:= TmwHashWord.Create(S);
end else
if TObject(Items[Length(S)]) is TmwHashStrings then
begin
    TmwHashStrings(Items[Length(S)]).AddString(S);
end else
begin
    HashWord:= Items[Length(S)];
    HashStrings:= TmwHashStrings.Create;
    Items[Length(S)]:= HashStrings;
    HashStrings.AddString(HashWord.S);
    HashWord.Free;
    HashStrings.AddString(S)
end;
end;

{ TmwStringHashList }

constructor TmwStringHashList.Create(aHash: TmwStringHash; aCompare: TmwStringHashCompare);
begin
inherited Create;
fHash:= aHash;
fCompare:= aCompare;
end;

procedure TmwStringHashList.AddString(S: String);
var
HashWord: TmwHashWord;
HashValue: Integer;
HashItems: TmwHashItems;
begin
HashValue:= fHash(S);
if HashEx(S, HashValue) then exit;
if HashValue >= fCapacity then SetCapacity(HashValue);
if Items[HashValue] = nil then
begin
    Items[HashValue]:= TmwHashWord.Create(S);
end else
if TObject(Items[HashValue]) is TmwHashItems then
begin
    TmwHashItems(Items[HashValue]).AddString(S);
end else
begin
    HashWord:= Items[HashValue];
    HashItems:= TmwHashItems.Create;
    Items[HashValue]:= HashItems;
    HashItems.AddString(HashWord.S);
    HashWord.Free;
    HashItems.AddString(S);
end;
end;

function TmwStringHashList.Hash(S: String): Boolean;
begin
Result:= HashEX(S, fHash(S));
end;

function TmwStringHashList.HashEX(S: String; HashValue: Integer): Boolean;
var
Temp: TObject;
Hashword: TmwHashWord;
HashItems: TmwHashItems;
I: Integer;
begin
Result:= False;
if HashValue < 1 then Exit;
if HashValue > Capacity then Exit;
if Items[HashValue] <> nil then
begin
    if TObject(Items[HashValue]) is TmwHashWord then
    begin
      Result:= fCompare(TmwHashWord(Items[HashValue]).S, S);
    end else
    begin
      HashItems:= Items[HashValue];
      if Length(S) > HashItems.Capacity then Exit;
      Temp:= HashItems[Length(S)];
      if Temp <> nil then
      if Temp is TmwHashWord then
      begin
        Result:= fCompare(TmwHashWord(Temp).S, S);
      end else
      for I:= 0 to TmwHashStrings(Temp).Count -1 do
      begin
        HashWord:= TmwHashStrings(Temp)[I];
        Result:= fCompare(HashWord.S, S);
        if Result then exit;
      end;
    end;
end;
end;

Initialization
InitTables;
end.