PowerBuilder

Write Text at a 32-bit Offset in a Remote SFTP File

Demonstrates the Chilkat SFtp.WriteFileText32 method, which encodes text and writes it at a specific 32-bit byte offset in an open handle. The arguments are the handle, the offset, the charset, and the text.

Background: Explicit-offset writes enable random access — patching a fixed-length record in place, for instance, without rewriting the whole file. The offset is a byte position, not a character position, so with a variable-width encoding like UTF-8 you must account for the encoded size of preceding characters to land where you intend. After the write, the sequential position continues just past the bytes written.

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integer li_rc
long li_Success
oleobject loo_Sftp
long li_Port
string ls_Password
string ls_Handle
long li_Offset

li_Success = 0

//  Demonstrates the SFtp.WriteFileText32 method, which encodes text and writes it at a specific
//  32-bit byte offset in an open handle.  The 1st argument is the handle, the 2nd is the offset,
//  the 3rd is the charset, and the 4th is the text.

loo_Sftp = create oleobject
li_rc = loo_Sftp.ConnectToNewObject("Chilkat.SFtp")
if li_rc < 0 then
    destroy loo_Sftp
    MessageBox("Error","Connecting to COM object failed")
    return
end if

//  Connect, authenticate, and initialize the SFTP subsystem.
li_Port = 22
li_Success = loo_Sftp.Connect("sftp.example.com",li_Port)
if li_Success = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
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.
ls_Password = "mySshPassword"

li_Success = loo_Sftp.AuthenticatePw("mySshLogin",ls_Password)
if li_Success = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
end if

li_Success = loo_Sftp.InitializeSftp()
if li_Success = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
end if

//  Open the remote file for read/write so an existing file can be modified in place.
ls_Handle = loo_Sftp.OpenFile("subdir/record.dat","readWrite","openOrCreate")
if loo_Sftp.LastMethodSuccess = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
end if

//  Overwrite 5 bytes starting at offset 10.  The offset is a byte position, not a character
//  position, so it must account for the encoded size of any multibyte characters.
li_Offset = 10
li_Success = loo_Sftp.WriteFileText32(ls_Handle,li_Offset,"utf-8","HELLO")
if li_Success = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
end if

li_Success = loo_Sftp.CloseHandle(ls_Handle)
if li_Success = 0 then
    Write-Debug loo_Sftp.LastErrorText
    destroy loo_Sftp
    return
end if

Write-Debug "Wrote at the specified offset."

loo_Sftp.Disconnect()


destroy loo_Sftp