Обработка пакетов

unit UMainForm;
 
 
interface
 
uses
  Classes, Forms, types, ExtCtrls, StdCtrls, Controls, Contnrs, SysUtils;
 
type
  TPacketRec = packed record
    header: word; // 0-1
    data: array[0..1927] of byte; // 2-1939
    counter: byte; // 1930
    reserved: array[0..3] of byte; // 1931-1934
    endMarker: word; // 1935-1936
  end;
 
  TPacketClass = class
  public
    packet: TPacketRec;
    function IsCorrect: boolean;
  end;
 
  TPacketList = class(TObjectList)
  private
    function GetItemas(index: integer): TPacketClass;
    procedure SetItems(index: integer; const Value: TPacketClass);
  public
    property Items[index: integer]: TPacketClass read GetItemas write SetItems;
  end;
 
  TfMainForm = class(TForm)
    b1: TButton;
    pnl1: TPanel;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure b1Click(Sender: TObject);
  private
    procedure ReadFile(filename:string);
  public
    list: TPacketList;
  end;
 
var
  fMainForm: TfMainForm;
 
implementation
 
{$R *.dfm}
 
function findPacketBegin(f: TFileStream; StartPos: integer): integer;
const
  BUF_SIZE = 4096;
var
  buf: array[0..BUF_SIZE - 1] of byte;
  i, n: integer;
begin
  result := -1;
  f.position := StartPos;
  repeat
    n := f.read(buf[0], BUF_SIZE);
    for i := 0 to n - 2 do
    begin
      if (buf[i] = $08) and (buf[i + 1] = $02) then
      begin
        result := i;
        f.position := result;
        exit;
      end
    end;
    f.Position := f.Position - 1; // если вдруг $08 - это последний байт буфера
  until n < BUF_SIZE;
 
  f.position := StartPos;
end;
 
function TPacketClass.IsCorrect: boolean;
begin
  result := (packet.header = $0208) and ((packet.endMarker = $0100) or (packet.endMarker = $0001));
end;
 
{ TPacketList }
 
function TPacketList.GetItemas(index: integer): TPacketClass;
begin
  result := inherited Items[index] as TPacketClass;
end;
 
procedure TPacketList.SetItems(index: integer; const Value: TPacketClass);
begin
  inherited Items[index] := Value;
end;
 
procedure TfMainForm.ReadFile(Filename:String);
var
  f: TFileStream;
  p: TPacketClass;
  ind, StartPos: integer;
begin
  StartPos := 0;
  f := TFileStream.Create(Filename, fmOpenRead);
  while f.size - f.position > SizeOf(TPacketRec) do
  begin
    ind := FindPacketBegin(f, StartPos);
    if ind <> -1 then
    begin
      p := TPacketClass.Create();
      f.read(p.packet, sizeof(p.packet));
      if p.IsCorrect then
      begin
        list.add(p)
      end
      else
      begin
        p.free;
        StartPos := StartPos + 2;
      end
    end;
  end;
 
  f.free;
end;
 
procedure TfMainForm.b1Click(Sender: TObject);
begin
  ReadFile('вашфайл') ;
  // сейчас в List содержится список найденных пакетов
end;
 
procedure TfMainForm.FormCreate(Sender: TObject);
begin
  list := TPacketList.Create();
end;
 
procedure TfMainForm.FormDestroy(Sender: TObject);
begin
  FreeAndNil(List);
end;
 
 
 
end.