| Description |
If the current stream has not been exhausted, the next character, or block of characters/bytes are returned.
The stream position is updated accordingly.
In the first syntax, the Read method returns the next stream character is returned as an integer. The integer value is the numeric equivalent of the character, or -1 if the string was exhausted.
In the second and third syntaxes, an attempt is made to read up to Count bytes/characters. These are overlaid onto the Bytes or Characters array as appropriate from StartIndex. The returned integer value is the number of bytes/characters overlaid. Zero if the string was already exhausted before the read.
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| | Notes | You must set the length of the target Byte/Character array in the second syntax, and it must have sufficient capacity to hold the returned bytes/characters.
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| Microsoft MSDN Links |
System.IO
System.IO.BinaryReader
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| Reading a single character at a time |
// 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;
{$APPTYPE CONSOLE}
uses
System.IO;
var
MyFileStream : System.IO.FileStream;
MyFileWriter : System.IO.BinaryWriter;
MyFileReader : System.IO.BinaryReader;
begin
// Create and open our binary file as a stream
MyFileStream := System.IO.File.Open('C:DelphiBasics.txt',
System.IO.FileMode.Create);
// Create a BinaryWriter to allow writing to this file
MyFileWriter := System.IO.BinaryWriter.Create(MyFileStream);
// Write to the file
MyFileWriter.Write('A');
MyFileWriter.Write('B');
MyFileWriter.Write('C');
// Close the writer and the stream
MyFileWriter.Close;
MyFileStream.Close;
// Reopen the stream for reading
MyFileStream := System.IO.File.Open('C:DelphiBasics.txt',
System.IO.FileMode.Open);
// Create a BinaryReader to allow the file to be read back
MyFileReader := System.IO.BinaryReader.Create(MyFileStream);
// Display the file contents
while MyFileReader.PeekChar <> -1 do
Console.WriteLine(Char(MyFileReader.Read));
// Close the reader and the stream
MyFileReader.Close;
MyFileStream.Close;
Console.Readline;
end.
end. | | Hide full unit code | A
B
C
| | | Reading blocks of characters | program Project1;
{$APPTYPE CONSOLE}
uses
System.IO;
var
MyFileStream : System.IO.FileStream;
MyFileWriter : System.IO.BinaryWriter;
MyFileReader : System.IO.BinaryReader;
MyCharArray : Array of Char;
Index : Integer;
begin
// Create and open our binary file as a stream
MyFileStream := System.IO.File.Open('C:DelphiBasics.txt',
System.IO.FileMode.Create);
// Create a BinaryWriter to allow writing to this file
MyFileWriter := System.IO.BinaryWriter.Create(MyFileStream);
// Write to the file
MyFileWriter.Write('A');
MyFileWriter.Write('B');
MyFileWriter.Write('C');
MyFileWriter.Write(49); // Chr(49) = '1'
MyFileWriter.Write(50); // Chr(50) = '2'
MyFileWriter.Write(51); // Chr(51) = '3'
MyFileWriter.Write(52); // Chr(52) = '4'
// Close the writer and the stream
MyFileWriter.Close;
MyFileStream.Close;
// Reopen the stream for reading
MyFileStream := System.IO.File.Open('C:DelphiBasics.txt',
System.IO.FileMode.Open);
// Create a BinaryReader to allow the file to be read back
MyFileReader := System.IO.BinaryReader.Create(MyFileStream);
// Declare our array to hold the returned data
SetLength(MyCharArray, 10);
// Get the file contents 3 characters at a time into our array
Index := 0;
while MyFileReader.PeekChar <> -1 do
begin
MyFileReader.Read(MyCharArray, index, 3);
Index := Index + 3;
end;
// Display our array contents
Console.WriteLine(MyCharArray);
// Close the reader and the stream
MyFileReader.Close;
MyFileStream.Close;
Console.Readline;
end.
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