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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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const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // 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.

    const sftp = try chilkat.SFtp.init();
    defer sftp.deinit();

    // Connect, authenticate, and initialize the SFTP subsystem.
    const port = 22;
    sftp.connect("sftp.example.com", port) catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        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.
    const password = "mySshPassword";

    sftp.authenticatePw("mySshLogin", password) catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    sftp.initializeSftp() catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    const handle = sftp.openFile(alloc, "subdir/data.txt", "readOnly", "openExisting") catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    var reading: bool = true;
    const chunk_size = 4096;
    const bd = try chilkat.BinData.init();
    defer bd.deinit();
    while (reading) {
        try sftp.readFileBd(handle, chunk_size, bd);

        // Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
        // zero bytes, and LastReadFailed is false.
        if (sftp.lastReadFailed(handle)) {
            std.debug.print("Read failed: {s}\n", .{try sftp.getLastErrorText(alloc)});
            return;
        }

        reading = !sftp.eof(handle);
    }

    sftp.closeHandle(handle) catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Read {d} bytes with no read failures.\n", .{bd.getNumBytes()});

    sftp.disconnect();
}