Delphi's TFileStream Memory stream

First, the document

A text file is read and written in the Unit of action. Text files can only be opened separately for reading or writing, and reading and writing on an open text file is not allowed at the same time.

Second, the definition

Filestream:tfilestream;

Third, open the file

filestream:= Tfilestream.create (afilename:string; Mode:word);

Parameter afilename: filename; mode: How the file is opened.

mode is composed of open mode and shared mode, and the values are shown in the following table:

Classification	Parameters	Description
Play Open Mode Expression	Fmcreate	Creates a file that opens in write mode if a file with the specified file name already exists
	Fmopenread	Read-Only Open
	Fmopenwrite	Open a file in write mode, and the contents of the file will replace the previous contents of the file
	Fmopenreadwrite	Read/write Open
Shared Enjoy Mode Expression	Fmsharecompat	Shared mode, Dos compatible
	Fmshareexclusive	His application cannot open the file
	Fmsharedenywrite	Other applications can only be opened in write-only mode
	Fmsharedenyread	Other applications can only be opened as read-only
	Fmsharedenynone	Other applications can open files in any way

Iv. Read and write files

function Read (var buffer;count:longint): Longint; Reads count bytes from the current location of the file stream to the buffer buffer;function write (const buffer;count:longint): Longint; Writes the count bytes of data for buffer buffers to the current location of the file stream, overwriting the data for count bytes after that location; function Seek (Offset:longint;origin:word): Longint; Set file stream current read/write pointer position, origin={sofrombeginning,sofromcurrent,sofromend}function CopyFrom (Source:tstream;count:longint) : Longint; Copies the count from the current location in another file stream to the current file stream current position;

　　

Viii. closing files

The file must be closed by calling Freeandnil (FileStream).

/////////////////////////////////////////////////////////////////////////////////////////////////////////////// An instance of//////////////////////////////////////////////////////////////////////////////////////////// Typetbuffer = array [0..16000]of charprocedure getmessagefromdir (afilename:string; var abuffer:tbuffer); var filestream:tfilestream;begin filestream:=tfilestream.create (Afilename,fmshareexclusiv       e);       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; ///////////////////////////////////////////////////////////////////////////////////////////An instance of//////////////////////////////////////////////////////////////////////// Procedure Tform1.button1click (sender:tobject); var getstream , Setstream:tfilestream; {Declare a file stream} getpath,setpath:string;begin getpath: = ' c:\temp\get.jpg '; {This file exists} SetPath: = ' c:\temp\set.jpg ';  {This will be automatically created} GetStream: = Tfilestream.create (GetPath, fmopenread or fmshareexclusive);  SetStream: = Tfilestream.create (SetPath, fmcreate); Getstream.position: = 0; {The flow pointer moves to the beginning, starting from here when copying} setstream.copyfrom (GetStream, getstream.size);  {Copy Stream}  {The second parameter of CopyFrom is the size of the content to be copied; if it is 0, all content will be copied wherever the pointer is located} getstream.free; Setstream.free;end; /////////////////////////////////////////////////////////////////////////////////////////////////////////////// One instance: Reading the picture data in the stream, displaying the picture//////////////////////////////////////////////////////////////////////////// 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); varbmp:tbitmap;  Begin Fstream:=tfilestream.create (Filename,fmopenread); FStream.  Seek (0,sofrombeginning);  Bmp:=tbitmap.create; Bmp.  Loadfromstream (FStream); Img1. Picture.bitmap:=bmp;end;   End.

　　

Delphi's TFileStream Memory stream