Xbase++

Check Whether the Last SFTP Read Failed

Demonstrates the Chilkat SFtp.LastReadFailed method, which returns whether the most recent read for a handle failed. The only argument is the handle. A normal end-of-file is not a failure.

Background: A chunked read loop needs to tell three outcomes apart: more data, a clean end-of-file, and an actual error such as a dropped connection or a revoked handle. LastReadFailed isolates the error case — it is false on a normal EOF read (which succeeds with zero bytes) and true for an empty, malformed, or already-closed handle — so the loop can stop cleanly on EOF but bail out with an error message on a genuine failure.

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LOCAL nSuccess
LOCAL oSftp
LOCAL nPort
LOCAL cPassword
LOCAL cHandle
LOCAL nReading
LOCAL nChunkSize
LOCAL oBd

nSuccess := 0

//  Demonstrates the SFtp.LastReadFailed method, which returns whether the most recent read for a
//  handle failed.  The only argument is the handle.  A normal end-of-file is NOT a failure.

oSftp := CreateObject("Chilkat.SFtp")

//  Connect, authenticate, and initialize the SFTP subsystem.
nPort := 22
nSuccess := oSftp:Connect("sftp.example.com", nPort)
IF (nSuccess == 0)
    ? oSftp:LastErrorText
    oSftp:destroy()
    RETURN
ENDIF

//  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.
cPassword := "mySshPassword"

nSuccess := oSftp:AuthenticatePw("mySshLogin", cPassword)
IF (nSuccess == 0)
    ? oSftp:LastErrorText
    oSftp:destroy()
    RETURN
ENDIF

nSuccess := oSftp:InitializeSftp()
IF (nSuccess == 0)
    ? oSftp:LastErrorText
    oSftp:destroy()
    RETURN
ENDIF

cHandle := oSftp:OpenFile("subdir/data.txt", "readOnly", "openExisting")
IF (oSftp:LastMethodSuccess == 0)
    ? oSftp:LastErrorText
    oSftp:destroy()
    RETURN
ENDIF

nReading := 1
nChunkSize := 4096
oBd := CreateObject("Chilkat.BinData")
DO WHILE nReading
    nSuccess := oSftp:ReadFileBd(cHandle, nChunkSize, oBd)

    //  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
    //  zero bytes, and LastReadFailed is 0.
    IF (oSftp:LastReadFailed(cHandle))
        ? "Read failed: " + oSftp:LastErrorText
        oSftp:destroy()
        oBd:destroy()
        RETURN
    ENDIF

    nReading := .NOT. oSftp:Eof(cHandle)
ENDDO

nSuccess := oSftp:CloseHandle(cHandle)
IF (nSuccess == 0)
    ? oSftp:LastErrorText
    oSftp:destroy()
    oBd:destroy()
    RETURN
ENDIF

? "Read " + Str(oBd:NumBytes) + " bytes with no read failures."

oSftp:Disconnect()

oSftp:destroy()
oBd:destroy()