记录文件实例与调用

unit MyRec;

interface
  uses
  windows,messages,classes,forms,sysutils;
type
  TPersonRec=packed record
    id:string[11];
    path:string[6];
    pic:string[35];
    tdate:string[10];
  end;
  TMyrec=class(Tfilestream)
  private
    function GetNumRecs:longint;
    function GetCurRec:longint;
    procedure SetCurRec(RecNum:longint);
  protected
    function GetRecSize:longint;virtual;
  public
    procedure DeleteRec(var Rec);
    function seekRec(RecNum:longint):longint;
    function WriteRec(const Rec):longint;
    function AppandRec(const Rec):longint;
    function ReadRec(var Rec):longint;
    procedure first;
    procedure last;
    procedure nextRec;
    procedure previouRec;
    property NumRecs:longint read GetNumRecs;
    property CurRec:longint read GetCurRec Write SetCurRec;
  end;

implementation

function TMyrec.GetRecSize:longint;   //取得单条记录的长度
begin
  Result:=sizeof(TPersonRec);
end;

function TMyRec.GetNumRecs:longint;   //取得记录总数
begin
  Result:=size div getRecsize;
end;

function TMyRec.GetCurRec;           //取得当前所在记录号
begin
  Result:=(position div GetRecsize)+1;
end;
                                   //前往某条记录
function TMyRec.seekRec(RecNum:integer):longint;
begin
  seek(0,0);
  Result:=seek((RecNum-1)*GetRecSize,1);
end;
                                   //写入记录
function TMyRec.WriteRec(const Rec):longint;
begin
  Result:=write(Rec,GetRecSize);
end;
                                   //增加记录
function TMyRec.AppandRec(const Rec):longint;
begin
  seek(0,2);   //to the end of then stream
  Result:=write(Rec,GetRecsize);
end;
                                //读取记录
function TMyRec.ReadRec(var Rec):longint;
begin
  result:=read(Rec,GetRecsize);
  seek(-GetRecsize,1);
end;
                              //删除记录
procedure TmyRec.DeleteRec(var Rec);
begin
  
end;
                                //前往某条记录
procedure TMyRec.SetCurRec(RecNum:integer);
begin
  if RecNum>0 then
   position:=(RecNum-1)*GetRecsize
end;
                                //第一条
procedure TMyRec.first;
begin
  seek(0,0);
end;
                                //最后一条
procedure TMyRec.last;
begin
  seek(0,2);
  seek(-getRecsize,1);
end;
                                //下一条
procedure TMyRec.nextRec;
begin
  if ((position+GetRecsize) div GetRecsize)<GetNumRecs then
    seek(GetRecsize,1)
end;
                                //前一条
procedure TMyRec.previouRec;
begin
   if (position-GetRecsize)>=0 then
    seek(-GetRecsize,1)
end;


end.

调用

 var
  Myrec:TMyrec;
  Rec:TPersonRec;

Myrec := TMyrec.Create('rec.dat',fmCreate or fmShareDenyWrite);
    Rec.id :='';
    Rec.path :='';
    Rec.pic :='';
    Rec.tdate :='';
    Myrec.AppandRec(Rec);