| Description |
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Count bytes from StartIndex are locked. This prevents other, concurrent processes writing to them.
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| | Notes | This is somewhat beyond Delphi Basics, so the example merely illustrates the syntax.
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| Microsoft MSDN Links |
System.IO
System.IO.FileStream
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| Illustrating the syntax |
// Full Unit code.
// -------------------------------------------------------------
// Create a new WinForm application, double click the form to
// create an OnLoad event, and then replace the WinForm unit
// with this text.
unit WinForm;
interface
uses
System.Drawing, System.Collections, System.ComponentModel,
System.Windows.Forms, System.Data;
type
TWinForm = class(System.Windows.Forms.Form)
\{REGION 'Designer Managed Code'\} // Note that REGION and ENREGION should be prefixed by a dollar sign
strict private
///
/// Required designer variable.
///
Components: System.ComponentModel.Container;
///
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
///
procedure InitializeComponent;
procedure TWinForm_Load(sender: System.Object; e: System.EventArgs);
{ENDREGION}
strict protected
///
/// Clean up any resources being used.
///
procedure Dispose(Disposing: Boolean); override;
private
{ Private Declarations }
public
constructor Create;
end;
[assembly: RuntimeRequiredAttribute(TypeOf(TWinForm))]
implementation
\{REGION 'Windows Form Designer generated code'\}
///
/// Required method for Designer support -- do not modify
/// the contents of this method with the code editor.
///
procedure TWinForm.InitializeComponent;
begin
//
// TWinForm
//
Self.AutoScaleBaseSize := System.Drawing.Size.Create(5, 13);
Self.ClientSize := System.Drawing.Size.Create(292, 266);
Self.Name := 'TWinForm';
Self.Text := 'WinForm';
Include(Self.Load, Self.TWinForm_Load);
end;
{ENDREGION}
procedure TWinForm.Dispose(Disposing: Boolean);
begin
if Disposing then
begin
if Components <> nil then
Components.Dispose();
end;
inherited Dispose(Disposing);
end;
constructor TWinForm.Create;
begin
inherited Create;
//
// Required for Windows Form Designer support
//
InitializeComponent;
//
// TODO: Add any constructor code after InitializeComponent call
//
end;
procedure TWinForm.TWinForm_Load(sender: System.Object; e: System.EventArgs);
program Project1;
{$APPTYPE CONSOLE}
uses
System.IO;
var
Stream : System.IO.FileStream;
i : Integer;
begin
// Open the file for writing
Stream := System.IO.FileStream.Create('C:\DelphiBasics.txt',
FileMode.Create);
// Write to the file
Stream.WriteByte(65); // Chr(65) = 'A'
Stream.WriteByte(66); // Chr(66) = 'B'
Stream.WriteByte(67); // Chr(67) = 'C'
Stream.WriteByte(68); // Chr(68) = 'D'
Stream.WriteByte(69); // Chr(69) = 'E'
// Lock the last 3 bytes for update
Stream.Lock(2, 3);
// Now any concurrent process will be unable to write to
// these last 3 bytes of the file.
// ... Run a concurrent process at this point
// Unlock the file
Stream.Unlock(2, 3);
// Close the stream
Stream.Close;
Console.Readline;
end.
end. | | Hide full unit code |
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