unit UByteStream;

interface

uses
  Sysutils, Classes;


type
  PByteStream = ^TByteStream;
  TByteStream = Class(TObject)
  private
    FFile: File Of Byte;
    FFileName: String;
  public
    constructor Create(AFileName: String; Mode: Word);
    destructor Destroy; override;
    function ReadByte: Byte;
    function Read(var Buffer: array of byte; BufSize: Longint): Longint;
    procedure WriteByte(b: Byte);
    function Write(var Buffer: array of byte; BufSize: Longint): Longint;
    function Position: Longint;
    function Size: Longint;
    procedure Seek(APos: Longint; Flag: Word);
  End;


implementation


{ TByteStream }

constructor TByteStream.Create(AFileName: String; Mode: Word);
var IResult: Integer;
begin
  inherited Create;
  System.Assign(FFile, FFileName);
  {$I-}
  if (Mode=fmOpen) or (Mode=fmOpenRead) then
  begin
    System.Reset(FFile);
    IResult := System.IOResult;
    if IResult <> 0 then fail;
  end
  else
  if Mode = fmCreate then
  begin
    System.Rewrite(FFile);
    IResult := IOResult;
    if IResult <> 0 then fail;
  end;
  {$I+}
end;

destructor TByteStream.Destroy;
begin
  System.Close(FFile);
  inherited Done;
end;

function TByteStream.ReadByte: Byte;
var b: Byte;
begin
  System.Read(FFile, b);
  Result := b;
end;

function TByteStream.Read(var Buffer: array of byte; BufSize: Longint): Longint;
var Count,Current,BufStart,BufEnd,BufPos: Word;
begin
  BufStart := Low(Buffer);
  BufEnd := High(Buffer);
  BufPos := BufStart;
  Current := System.FilePos(FFile);
  Count := Current;
  while Count < Current + BufSize do
  begin
    System.Read(FFile, Buffer[BufPos]);
    inc(BufPos);
    inc(Count);
  end;
  Result := Count - Current;
end;

procedure TByteStream.WriteByte(b: Byte);
begin
  System.Write(FFile, b);
end;

function TByteStream.Write(var Buffer: array of byte; BufSize: Longint): Longint;
var Count,Current,BufStart,BufEnd,BufPos: Word; x: array[0..1023] of byte absolute Buffer;
begin
  BufStart := Low(Buffer);
  BufEnd := High(Buffer);
  BufPos := BufStart;
  Current := System.FilePos(FFile);
  Count := Current;
  while Count < Current + BufSize do
  begin
    System.Write(FFile, Buffer[BufPos]);
    inc(BufPos);
    inc(Count);
  end;
  Result := Count - Current;
end;

function TByteStream.Position: Longint;
begin
  Result := System.FilePos(FFile);
end;

function TByteStream.Size: Longint;
begin
  Result := System.FileSize(FFile);
end;

procedure TByteStream.Seek(APos: Longint; Flag: Word);
begin
  case Flag of
    soFromBeginning: System.Seek(FFile, APos);
    soFromCurrentPos: ;
    soFromEnd: ;
  end;
end;

end.

type
  TReader = class(TObject)
   private
    MeineBytes: TByteStream;
   public
    constructor Create(Filename: String);
    destructor Destroy; override;
    procedure ReadBytes;
  end;

implementation

constructor Create(Filename: String);
begin
  inherited Create;
  MeineBytes := TByteFile.Create(FileName, fmOpen);
end;

destructor Destroy;
begin
  MeineBytes.Free;
  inherited Destroy;
end;

procedure ReadBytes;
begin
  //hier sollten die Bytes aus der Datei nun gelesen werden
  //Aber die Datei ist nicht geöffnet
end;

end.