VB.NET

Read Text at a 64-bit Offset from a Remote SFTP File

Demonstrates the Chilkat SFtp.ReadFileText64 method, which reads up to a number of bytes from a specific 64-bit byte offset of an open handle and decodes them to text. The arguments are the handle, the offset, the maximum number of bytes, and the charset. The 64-bit offset supports very large files.

Background: This is the large-file counterpart to reading at a 32-bit offset: use it whenever the position you need lies beyond the ~4 GB reach of a 32-bit integer, for example seeking into a multi-gigabyte archive or database file. Everything else about the read is the same.

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Dim success As Boolean = False

'  Demonstrates the SFtp.ReadFileText64 method, which reads up to a number of bytes from a
'  specific 64-bit byte offset of an open handle and decodes them to text.  The 1st argument is
'  the handle, the 2nd is the offset, the 3rd is the maximum number of bytes, and the 4th is the
'  charset.  The 64-bit offset supports very large files.

Dim sftp As New Chilkat.SFtp

'  Connect, authenticate, and initialize the SFTP subsystem.
Dim port As Integer = 22
success = sftp.Connect("sftp.example.com",port)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  Normally you would not hard-code the password in source.  You should instead obtain it
'  from an interactive prompt, environment variable, or a secrets vault.
Dim password As String = "mySshPassword"

success = sftp.AuthenticatePw("mySshLogin",password)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


success = sftp.InitializeSftp()
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


Dim handle As String = sftp.OpenFile("subdir/hugefile.dat","readOnly","openExisting")
If (sftp.LastMethodSuccess = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  Read 6 bytes starting at a byte offset beyond the 32-bit (4 GB) range.
Dim offset As Long = 5000000000
Dim numBytes As Integer = 6
Dim text As String = sftp.ReadFileText64(handle,offset,numBytes,"utf-8")
If (sftp.LastMethodSuccess = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If

Debug.WriteLine(text)

success = sftp.CloseHandle(handle)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


sftp.Disconnect()