Imports Microsoft.VisualBasic
Imports System
Imports System.IO

Imports Xceed.SSH.Client
Imports Xceed.SSH.Protocols
Imports Xceed.SSH.Core
Imports Xceed.FileSystem

Namespace DocumentationExamples.SSH
  Public Class ManualCopyTo
    Public Shared Sub Example()
      Dim host As String = "sftptest.dreamhosters.com"
      Dim username As String = "snippet_sftp"
      Dim password As String = "9MNfGgSx"

      Using ssh As New SSHClient()
        ssh.Connect(host)
        ssh.Authenticate(username, password)

        ' Start a SFtp session from the SSH client
        Using sftp As New SFtpSession(ssh)
          ' Select a local file
          Dim sourceFile As AbstractFile = New DiskFile("SomeFile.dat")

          ' Select a remote destination folder
          Dim destinationFolder As AbstractFolder = New SFtpFolder(sftp, "SomeFolder")

          ' Select the destination file in the destination folder using the name of the source file
          Dim destinationFile As AbstractFile = destinationFolder.GetFile(sourceFile.Name)

          If (Not sourceFile.Exists) Then
            Throw New InvalidOperationException("Source file does not exist.")
          End If

          If sourceFile.IsSameAs(destinationFile) Then
            Throw New InvalidOperationException("Cannot copy a file unto itself.")
          End If

          ' Open the source file for reading
          Using sourceStream As Stream = sourceFile.OpenRead()
            Dim destinationStream As Stream = Nothing

            Try
              ' If the destination file already exists
              If destinationFile.Exists Then
                ' Open it for writing, overwriting its previous contents
                destinationStream = destinationFile.OpenWrite(True)
              Else
                ' Create it and open it for writing in one operation
                destinationStream = destinationFile.CreateWrite()
              End If

'               SSH has an overhead and several rules that define a maximum logical packet
'               size.
'               
'               We are free to use any reasonable buffer size we want and it will work.
'               However, using a value too small will generate more overhead than needed.
'               Using a value too large will force the component to split the data into
'               several packets and increase overhead as well.
'                
'               SFtpSession has a method that computes the optimal buffer size for the
'               SFtp stream. It takes into account the effective overhead packets will have
'               and computes a value that will make it so that every call to Stream.Write()
'               will end up creating the biggest SSH packet allowed by the server that does
'               not generate extra overhead.
'                
'               This provides the best throughput in a file transfer. 
              Dim bufferSize As Integer = sftp.ComputeStreamBufferSize(destinationStream)

              ' Create a buffer for the streams
              Dim buffer(bufferSize - 1) As Byte
              Dim read As Integer

              ' While we have data to read from the source stream
              read = sourceStream.Read(buffer, 0, bufferSize)
              Do While read > 0
                ' Write the data to the destination stream
                destinationStream.Write(buffer, 0, read)
                read = sourceStream.Read(buffer, 0, bufferSize)
              Loop
            Finally
              ' If we have a destination stream
              If destinationStream IsNot Nothing Then
                ' Close it
                destinationStream.Close()
              End If
            End Try
          End Using
        End Using
      End Using
    End Sub
  End Class
End Namespace