{-----------------------------------------------------------------------------
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.