unit dpgrtl.tokenbuffer;

interface
uses
   dpgrtl.types,
   dpgrtl.inputbuffer,
   dpgrtl.tokenqueue;

type
   TTokenBuffer = class( TInputBuffer, IInputBuffer, ITokenBuffer)
      protected
         fStream  : ITokenStream;
         fQueue   : TTokenQueue;

      // ------------------------------------------------------------
      // Internals
      // ------------------------------------------------------------
      protected
         function    GetNext: IToken; inline;
         procedure   Fill( Amount: integer);

      // ------------------------------------------------------------
      // TInputBuffer override
      // ------------------------------------------------------------
      protected
         procedure   Remove( Num: integer); override;

      // ------------------------------------------------------------
      // ITokenBuffer
      // ------------------------------------------------------------
      protected
         function    LA(i: integer): integer;
         function    LT(i: integer): IToken;

      public
         constructor Create( AStream: ITokenStream);

         procedure   AfterConstruction; override;
         procedure   BeforeDestruction; override;
   end;

implementation

{ TTokenBuffer }

// @@@: Construction/destruction ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                   Construction/destruction
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Constructor
// ================================================================================================
constructor TTokenBuffer.Create(AStream: ITokenStream);
begin
   inherited Create;
   fStream := AStream;
end;

// ================================================================================================
// After Construction
// ================================================================================================
procedure TTokenBuffer.AfterConstruction;
begin
   inherited;
   fQueue := TTokenQueue.Create
end;

// ================================================================================================
// Before Destruction
// ================================================================================================
procedure TTokenBuffer.BeforeDestruction;
begin
   fStream := nil;
   fQueue.Free;
   inherited
end;



// @@@: ITokenBuffer implementation +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                  ITokenBuffer implementation
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// LA
//
//    Ensure that the 'fQueue' object hold sufficient tokens, and gets the 'i'th LookAhead token
//    type from the 'fQueue'.
// ================================================================================================
function TTokenBuffer.LA(i: integer): integer;
begin
   Fill(i);
   result := fQueue.Items[ fMarkerOffset +i -1].TokenType
end;

// ================================================================================================
// LT
// ================================================================================================
function TTokenBuffer.LT(i: integer): IToken;
begin
   Fill(i);
   result := fQueue.Items[ fMarkerOffset +i -1]
end;



// @@@: Internals +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                           Internals
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Get Next
// ================================================================================================
function TTokenBuffer.GetNext: IToken;
begin
   result := fStream.NextToken
end;

// ================================================================================================
// Fill
// ================================================================================================
procedure TTokenBuffer.Fill(Amount: integer);
begin
   SyncConsume;

   while fQueue.Count < (Amount +fMarkerOffset) do
      fQueue.Add( GetNext);
end;

// @@@: TInputBuffer overrides ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                    TInputBuffer overrides
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Remove
// ================================================================================================
procedure TTokenBuffer.Remove(Num: integer);
begin
   fQueue.Remove(Num)
end;

end.