BufferedStream Class
Adds a buffering layer to read and write operations on another stream. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
For an example of creating a file and writing text to a file, see How to: Write Text to a File. For an example of reading text from a file, see How to: Read Text from a File. For an example of reading from and writing to a binary file, see How to: Read and Write to a Newly Created Data File.
A buffer is a block of bytes in memory used to cache data, thereby reducing the number of calls to the operating system. Buffers improve read and write performance. A buffer can be used for either reading or writing, but never both simultaneously. The Read and Write methods of BufferedStream automatically maintain the buffer.
BufferedStream can be composed around certain types of streams. It provides implementations for reading and writing bytes to an underlying data source or repository. Use BinaryReader and BinaryWriter for reading and writing other data types. BufferedStream is designed to prevent the buffer from slowing down input and output when the buffer is not needed. If you always read and write for sizes greater than the internal buffer size, then BufferedStream might not even allocate the internal buffer. BufferedStream also buffers reads and writes in a shared buffer. It is assumed that you will almost always be doing a series of reads or writes, but rarely alternate between the two of them.
The following code example shows how to use the BufferedStream class over the NetworkStream class to increase the performance of certain I/O operations. Start the server on a remote computer before starting the client. Specify the remote computer name as a command-line argument when starting the client. Vary the dataArraySize and streamBufferSize constants to view their effect on performance.
' Compile using /r:System.dll. Imports Microsoft.VisualBasic Imports System Imports System.IO Imports System.Globalization Imports System.Net Imports System.Net.Sockets Public Class Client Const dataArraySize As Integer = 100 Const streamBufferSize As Integer = 1000 Const numberOfLoops As Integer = 10000 Shared Sub Main(args As String()) ' Check that an argument was specified when the ' program was invoked. If args.Length = 0 Then Console.WriteLine("Error: The name of the host " & _ "computer must be specified when the program " & _ "is invoked.") Return End If Dim remoteName As String = args(0) ' Create the underlying socket and connect to the server. Dim clientSocket As New Socket(AddressFamily.InterNetwork, _ SocketType.Stream, ProtocolType.Tcp) clientSocket.Connect(New IPEndPoint( _ Dns.Resolve(remoteName).AddressList(0), 1800)) Console.WriteLine("Client is connected." & vbCrLf) ' Create a NetworkStream that owns clientSocket and then ' create a BufferedStream on top of the NetworkStream. Dim netStream As New NetworkStream(clientSocket, True) Dim bufStream As New _ BufferedStream(netStream, streamBufferSize) Try ' Check whether the underlying stream supports seeking. If bufStream.CanSeek Then Console.WriteLine("NetworkStream supports" & _ "seeking." & vbCrLf) Else Console.WriteLine("NetworkStream does not " & _ "support seeking." & vbCrLf) End If ' Send and receive data. If bufStream.CanWrite Then SendData(netStream, bufStream) End If If bufStream.CanRead Then ReceiveData(netStream, bufStream) End If Finally ' When bufStream is closed, netStream is in turn ' closed, which in turn shuts down the connection ' and closes clientSocket. Console.WriteLine(vbCrLf & "Shutting down the connection.") bufStream.Close() End Try End Sub Shared Sub SendData(netStream As Stream, bufStream As Stream) Dim startTime As DateTime Dim networkTime As Double, bufferedTime As Double ' Create random data to send to the server. Dim dataToSend(dataArraySize - 1) As Byte Dim randomGenerator As New Random() randomGenerator.NextBytes(dataToSend) ' Send the data using the NetworkStream. Console.WriteLine("Sending data using NetworkStream.") startTime = DateTime.Now For i As Integer = 1 To numberOfLoops netStream.Write(dataToSend, 0, dataToSend.Length) Next i networkTime = DateTime.Now.Subtract(startTime).TotalSeconds Console.WriteLine("{0} bytes sent in {1} seconds." & vbCrLf, _ numberOfLoops * dataToSend.Length, _ networkTime.ToString("F1")) ' Send the data using the BufferedStream. Console.WriteLine("Sending data using BufferedStream.") startTime = DateTime.Now For i As Integer = 1 To numberOfLoops bufStream.Write(dataToSend, 0, dataToSend.Length) Next i bufStream.Flush() bufferedTime = DateTime.Now.Subtract(startTime).TotalSeconds Console.WriteLine("{0} bytes sent In {1} seconds." & vbCrLf, _ numberOfLoops * dataToSend.Length, _ bufferedTime.ToString("F1")) ' Print the ratio of write times. Console.Write("Sending data using the buffered " & _ "network stream was {0}", _ (networkTime/bufferedTime).ToString("P0")) If bufferedTime < networkTime Then Console.Write(" faster") Else Console.Write(" slower") End If Console.WriteLine(" than using the network stream alone.") End Sub Shared Sub ReceiveData(netStream As Stream, bufStream As Stream) Dim startTime As DateTime Dim networkTime As Double, bufferedTime As Double = 0 Dim bytesReceived As Integer = 0 Dim receivedData(dataArraySize - 1) As Byte ' Receive data using the NetworkStream. Console.WriteLine("Receiving data using NetworkStream.") startTime = DateTime.Now While bytesReceived < numberOfLoops * receivedData.Length bytesReceived += netStream.Read( _ receivedData, 0, receivedData.Length) End While networkTime = DateTime.Now.Subtract(startTime).TotalSeconds Console.WriteLine("{0} bytes received in {1} " & _ "seconds." & vbCrLf, _ bytesReceived.ToString(), _ networkTime.ToString("F1")) ' Receive data using the BufferedStream. Console.WriteLine("Receiving data using BufferedStream.") bytesReceived = 0 startTime = DateTime.Now Dim numBytesToRead As Integer = receivedData.Length Dim n As Integer Do While numBytesToRead > 0 'Read my return anything from 0 to numBytesToRead n = bufStream.Read(receivedData, 0, receivedData.Length) 'The end of the file is reached. If n = 0 Then Exit Do End If bytesReceived += n numBytesToRead -= n Loop bufferedTime = DateTime.Now.Subtract(startTime).TotalSeconds Console.WriteLine("{0} bytes received in {1} " & _ "seconds." & vbCrLf, _ bytesReceived.ToString(), _ bufferedTime.ToString("F1")) ' Print the ratio of read times. Console.Write("Receiving data using the buffered " & _ "network stream was {0}", _ (networkTime/bufferedTime).ToString("P0")) If bufferedTime < networkTime Then Console.Write(" faster") Else Console.Write(" slower") End If Console.WriteLine(" than using the network stream alone.") End Sub End Class
' Compile using /r:System.dll. Imports Microsoft.VisualBasic Imports System Imports System.Net Imports System.Net.Sockets Public Class Server Shared Sub Main() ' This is a Windows Sockets 2 error code. Const WSAETIMEDOUT As Integer = 10060 Dim serverSocket As Socket Dim bytesReceived As Integer Dim totalReceived As Integer = 0 Dim receivedData(2000000-1) As Byte ' Create random data to send to the client. Dim dataToSend(2000000-1) As Byte Dim randomGenerator As New Random() randomGenerator.NextBytes(dataToSend) Dim ipAddress As IPAddress = _ Dns.Resolve(Dns.GetHostName()).AddressList(0) Dim ipEndpoint As New IPEndPoint(ipAddress, 1800) ' Create a socket and listen for incoming connections. Dim listenSocket As New Socket(AddressFamily.InterNetwork, _ SocketType.Stream, ProtocolType.Tcp) Try listenSocket.Bind(ipEndpoint) listenSocket.Listen(1) ' Accept a connection and create a socket to handle it. serverSocket = listenSocket.Accept() Console.WriteLine("Server is connected." & vbCrLf) Finally listenSocket.Close() End Try Try ' Send data to the client. Console.Write("Sending data ... ") Dim bytesSent As Integer = serverSocket.Send( _ dataToSend, 0, dataToSend.Length, SocketFlags.None) Console.WriteLine("{0} bytes sent." & vbCrLf, _ bytesSent.ToString()) ' Set the timeout for receiving data to 2 seconds. serverSocket.SetSocketOption(SocketOptionLevel.Socket, _ SocketOptionName.ReceiveTimeout, 2000) ' Receive data from the client. Console.Write("Receiving data ... ") Try Do bytesReceived = serverSocket.Receive( _ receivedData, 0, receivedData.Length, _ SocketFlags.None) totalReceived += bytesReceived Loop While bytesReceived <> 0 Catch e As SocketException If(e.ErrorCode = WSAETIMEDOUT) ' Data was not received within the given time. ' Assume that the transmission has ended. Else Console.WriteLine("{0}: {1}" & vbCrLf, _ e.GetType().Name, e.Message) End If Finally Console.WriteLine("{0} bytes received." & vbCrLf, _ totalReceived.ToString()) End Try Finally serverSocket.Shutdown(SocketShutdown.Both) Console.WriteLine("Connection shut down.") serverSocket.Close() End Try End Sub End Class
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.