Check Whether the Last SFTP Read Failed

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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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#include <C_CkSFtp.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSFtp sftp;
    int port;
    const char *password;
    const char *handle;
    BOOL reading;
    int chunkSize;
    HCkBinData bd;

    success = FALSE;

    //  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.

    sftp = CkSFtp_Create();

    //  Connect, authenticate, and initialize the SFTP subsystem.
    port = 22;
    success = CkSFtp_Connect(sftp,"sftp.example.com",port);
    if (success == FALSE) {
        printf("%s\n",CkSFtp_lastErrorText(sftp));
        CkSFtp_Dispose(sftp);
        return;
    }

    //  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.
    password = "mySshPassword";

    success = CkSFtp_AuthenticatePw(sftp,"mySshLogin",password);
    if (success == FALSE) {
        printf("%s\n",CkSFtp_lastErrorText(sftp));
        CkSFtp_Dispose(sftp);
        return;
    }

    success = CkSFtp_InitializeSftp(sftp);
    if (success == FALSE) {
        printf("%s\n",CkSFtp_lastErrorText(sftp));
        CkSFtp_Dispose(sftp);
        return;
    }

    handle = CkSFtp_openFile(sftp,"subdir/data.txt","readOnly","openExisting");
    if (CkSFtp_getLastMethodSuccess(sftp) == FALSE) {
        printf("%s\n",CkSFtp_lastErrorText(sftp));
        CkSFtp_Dispose(sftp);
        return;
    }

    reading = TRUE;
    chunkSize = 4096;
    bd = CkBinData_Create();
    while (reading) {
        success = CkSFtp_ReadFileBd(sftp,handle,chunkSize,bd);

        //  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
        //  zero bytes, and LastReadFailed is FALSE.
        if (CkSFtp_LastReadFailed(sftp,handle)) {
            printf("Read failed: %s\n",CkSFtp_lastErrorText(sftp));
            CkSFtp_Dispose(sftp);
            CkBinData_Dispose(bd);
            return;
        }

        reading = !CkSFtp_Eof(sftp,handle);
    }

    success = CkSFtp_CloseHandle(sftp,handle);
    if (success == FALSE) {
        printf("%s\n",CkSFtp_lastErrorText(sftp));
        CkSFtp_Dispose(sftp);
        CkBinData_Dispose(bd);
        return;
    }

    printf("Read %d bytes with no read failures.\n",CkBinData_getNumBytes(bd));

    CkSFtp_Disconnect(sftp);


    CkSFtp_Dispose(sftp);
    CkBinData_Dispose(bd);

    }