function IsTextFile(FileName:string):boolean; 
var 
Fs:TFileStream; 
i,size:integer; 
IsTextFile:boolean; 
ByteData:Byte; 
begin 
if FileExists(FileName) then 
begin 
Fs:=TFileStream.Create(FileName,fmOpenRead); 
IsTextFile:=true; 
i:=0; 
size:=Fs.Size; 
While (i<size) and IsTextFile do 
begin 
Fs.Read(ByteData,1); 
IsTextFile:=ByteData<>0; 
inc(i) 
end; 
Fs.Free; 
Result:=IsTextFile 
end 
else 
Result:=false 
end;

Filestream:= TFileStream.Create(AFileName: string; Mode: Word);

function read(var buffer;count:longint):longint; //从文件流当前位置读count字节到缓冲区BUFFER；
function write(const buffer;count:longint):longint; //将缓冲区BUFFER的Count个字节的数据写到文件流当前位置中，覆盖该位置后面的Count个字节的数据；
function seek(offset:longint;origin:word):longint; //设置文件流当前读写指针位置，origin={soFromBeginning,soFromCurrent,soFromEnd}
function copyfrom(source:TStream;count:longint):longint; //从另一文件流中当前位置复制COUNT到当前文件流当前位置；

type
TBuffer = array [0..16000]of char
procedure GetMessageFromDir( AFileName: string; var ABuffer: TBuffer);
var
     FileStream: TFileStream;
begin
       Filestream:=TFileStream.Create(AFileName,fmShareExclusive);
       Filestream.Position:=0;
       FileStream.Read(ABuffer,sizeof(ABuffer));
     FreeAndNil(FileStream);
end;
procedure PutMessageToDir(AFileName:string; Astr :string);
var
     FileStream: TFileStream;
     tempBuffer:TBuffer;
begin
     StrPcopy(tempBuffer,Astr);
     Filestream:=TFileStream.Create(AFileName,fmShareExclusive or fmCreate);
     FileStream.Position:=0;
     FileStream.Write(tempBuffer,length(AStr));
     FreeAndNil(FileStream);
end;
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
一个实例
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TForm1.Button1Click(Sender: TObject);
var
getStream,setStream: TFileStream; {声明一个文件流}
getPath,setPath: string;
begin
getPath := 'c:\temp\get.jpg'; {这个文件存在}
setPath := 'c:\temp\set.jpg'; {这个会自动建立}
getStream := TFileStream.Create(getPath, fmOpenRead or fmShareExclusive);
setStream := TFileStream.Create(setPath, fmCreate);
getStream.Position := 0; {流指针移到开始, 复制时从这里开始}
setStream.CopyFrom(getStream, getStream.Size); {Copy 流}
{CopyFrom 的第二个参数是要复制的内容大小; 如果为 0 , 不管指针在什么位置都会复制所有内容}
getStream.Free;
setStream.Free;
end;
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
一个实例：读取流中的图片数据，显示图片
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
type
TForm1 = class(TForm)
    img1: TImage;
    procedure FormShow(Sender: TObject);
private
    { Private declarations }
public
    { Public declarations }
    fstream:TFileStream;
end;
var
Form1: TForm1;
filename:string = '.\WeiMir.uib';
implementation
{$R *.dfm}
procedure TForm1.FormShow(Sender: TObject);
var
bmp:Tbitmap;
begin
fstream:=Tfilestream.create(filename,fmOpenRead);
fstream.Seek(0,soFromBeginning);
bmp:=TBitmap.Create;
bmp.LoadFromStream(fstream);
img1.Picture.Bitmap:=bmp;
end;
end.