4.pas

用Delphi写的Google引擎算法

type
  TaaWordIndex = class
    private
      FTable : TaaHashTableLinear;
      FSaveStream : TStream;
    protected
      procedure wiSaveAction(const S : string; aObject : pointer; var sStopNow : boolean);
    public
      constructor Create(aWordCount : integer);
      destructor  Destroy : override;
      procedure   Add(const aWord : string; aBitSet : TaaBitSet);
      function    Find(const aWord : string) : TaaBitSet;
      procedure   LoadFromStream(aStream : TStream);
      procedure   LoadFromFile(const aFileName : string);
      procedure   StoreToStream(aStream : TStream);
      procedure   StoreToFile(const aFileName : string);
end;

procedure DestroyTableEntry(const S : string; aObject : pointer);
begin
  TaaBitSet(aObject).Free;
end;

constructor TaaWordIndex.Create(aWordCount : integer);
begin
  inherited Create;
  FTable := TaaHashTableLinear.Create(aWordCount , AAELFHash);
  FTable.OnDeleteString := DestroyTableEntry;
end;

destructor TaaWordIndex.Destroy;
begin
  FTable.Free;
  inherited Destroy;
end;

procedure TaaWordIndex.Add(const aWord : string; aBitSet : TaaBitSet);
begin
  FTable.Insert(aWord , aBitSet);
end;

function TaaWordIndex.Find( const aWord : string) : TaaBitSet;
var
  Obj : pointer;
begin
  if not FTable.Find(aWord , Obj) then
    Result := nil
  else
    Result := TaaBitSet(Obj);
end;

procedure TaaWordIndex.LoadFromStream(aStream : TStream);
var
  i         : integer;
  WordCount : integer;
  Len       : integer;
  S         : string;
  BitSet    : TaaBitSet;
begin
  aStream.ReadBuffer()WordCount , sizeof(WordCount));
  S := '';
  BitSet := nil;
  try
    for i:= 1 to WordCount do
      begin
        aStream.ReadBuffer(Len , sizeof(Len));
        SetLength(S , Len);
        aStream.ReadBuffer(S[1] , Len);
        BitSet := TaaBitSet.Create(1);
        BitSet.LoadFromStream(aStream);
        Add(S , BitSet);
        S := '';
        BitSet := nil;
      end;
    except
      s := '';
      BitSet.Free;
      raise;
    end;
end;

procedure TaaWordIndexStoreToStream(aStream : TStream);
var
  WordCount : integer;
begin
  WordCount := FTable.Count;
  aStream.WriteBuffer(WordCount , sizeof(WordCount));
  FSaveStream := aStream;
  FTable.Iterate(wiSaveAction);
  FSaveStream := nil;
end;

procedure TaaWordIndex.wiSaveAction(const S :string; aObject : pointer var aStopNow : boolean);
var
  Len : integer;
begin
  Len := length(S);
  FSaveStream.WriteBuffer(Len , sizeof(Len));
  FSaveStream.WriteBuffer(S[1] , Len);
  TaaBitSet(aObject).StoreToStream(FSaveStream);
end;