Zig

Monitor and Cancel a Running DKIM Operation

Demonstrates the Chilkat Dkim.HeartbeatMs and Dkim.AbortCurrent properties, which monitor and cancel a long-running operation such as a DNS public-key lookup. HeartbeatMs sets how often an AbortCheck event fires, and AbortCurrent requests cancellation.

Background: Most Dkim work is instant, but anything touching DNS can stall on a slow or unresponsive server. HeartbeatMs makes the object emit a periodic AbortCheck callback during such calls so an application stays responsive and can show progress, and AbortCurrent — set from that callback or from another thread — breaks a blocked synchronous call out early. Together they turn an otherwise uninterruptible operation into a cancellable one.

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Zig

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

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

    // Demonstrates the Dkim properties HeartbeatMs and AbortCurrent, which monitor and cancel a
    // long-running operation such as a DNS public-key lookup.

    const dkim = try chilkat.Dkim.init();
    defer dkim.deinit();

    // Fire an AbortCheck event callback every 100 ms during method calls.  In programming languages
    // where Chilkat supports event callbacks, the callback can request cancellation.
    dkim.setHeartbeatMs(100);

    // AbortCurrent may be set to true to request cancellation of a running operation.  It is
    // typically set from another thread, or from within an AbortCheck callback.  Setting it false
    // here ensures the operation is not pre-emptively aborted.
    dkim.setAbortCurrent(false);

    // PrefetchPublicKey performs a synchronous DNS lookup, which HeartbeatMs monitors and
    // AbortCurrent can cancel.
    dkim.prefetchPublicKey("myselector", "example.com") catch {
        std.debug.print("{s}\n", .{try dkim.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Public key prefetched.\n", .{});
}