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改良版TStringList类

 2006-02-04 14:08:05 来源:WEB开发网   
核心提示: {-The contents of this file are subject to the Mozilla Public License Version1.1 (the "License"); you may not use this file except in compliance with
 

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

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