// TODO: jo lenne cache-elni az LA(x) karaktereket...

unit dpgrtl.charbuffer;

interface
uses
   System.Classes,
   dpgrtl.types,
   dpgrtl.inputbuffer,
   dpgrtl.charqueue;

type
   TCharBuffer = class( TInputBuffer, IInputBuffer, ICharBuffer)
      protected
         fStream  : TStream;
         fQueue   : TCharQueue;

      protected
         function    GetNext: AnsiChar;
         procedure   Fill( Amount: integer);

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

      // ------------------------------------------------------------
      // ICharBuffer
      // ------------------------------------------------------------
      protected
         function    LA( i: integer): AnsiChar;

      // ------------------------------------------------------------
      // Construction/destruction
      // ------------------------------------------------------------
      public
         constructor Create( AStream: TStream);

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

implementation

{ TCharBuffer }

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

// ================================================================================================
// After Destruction
// ================================================================================================
procedure TCharBuffer.AfterConstruction;
begin
   inherited;

   fMarkerCount   := 0;
   fMarkerOffset  := 0;
   fNumToConsume  := 0;

   fQueue         := TCharQueue.Create
end;

// ================================================================================================
// Before Destruction
// ================================================================================================
procedure TCharBuffer.BeforeDestruction;
begin
   fQueue.Free;
   inherited
end;

// @@@: Interface +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                           Interface
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// LA
//
//    Ensures that the 'fQueue' object holds sufficient characters, and gets the 'i'th Look Ahead
//    character from the 'fQueue'.
// ================================================================================================
function TCharBuffer.LA(i: integer): AnsiChar;
begin
   Fill(i);
   result := fQueue.Items[fMarkerOffset +i]
end;

// @@@: Internals +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                           Internals
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Get Next
// ================================================================================================
function TCharBuffer.GetNext: AnsiChar;
begin
   if fStream.Read( result, 1) <> 1 then
      result := #0
end;

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

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

// @@@: Overrides +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                           Overrides
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Remove
// ================================================================================================
procedure TCharBuffer.Remove(ACount: integer);
begin
   fQueue.Remove(ACount)
end;

end.