Hsu.Formats.Replay 2026.7.13

Hsu.Formats.Replay

Replay engine for the Hsu.Formats toolkit. It schedules recorded CAN trace logs (ASC, BLF, TRC, MDF, KME), mixed CAN + Ethernet trace logs (ASC, BLF), and pure Ethernet captures (PCAP, PCAPNG), then emits replay items over an Ethernet network transport (UDP in the current release).

This library does not capture or record — it replays recordings produced by the Hsu.Formats.Trace parsers.

Pipeline

file ─▶ streaming parser ─▶ ReplayPlanBuilder ─▶ ReplayPlan
                                                │
                ReplaySession (timing/speed/loop/pause/max-idle-gap)
                                                ▼
                           IReplayTransport / UdpReplayTransport / UdpDuplexTransport

Supported parser categories consumed by ReplayPlanBuilder:

• IAsyncStreamingEventParser — mixed CAN + Ethernet trace logs
• IAsyncStreamingTraceParser — frame-oriented CAN trace logs
• IAsyncStreamingEthernetParser — Ethernet packet captures

Key Types

Features

• Replays CAN trace recordings and Ethernet captures over UDP transports
• Preserves original inter-item timing with optional speed scaling
• Optional looping playback
• Pause/resume support without counting paused wall-clock time against playback timing
• Optional MaxIdleGap compression for long silences in the source recording
• Progress notifications after each item is sent
• Duplex-response comparison support for replay/response workflows
• Distinguishes CAN and Ethernet replay payloads on wire through a shared replay protocol prefix and typed payload kind
• Supports both desktop UI and command-line execution paths on the desktop host

Quick Start

Replay an ASC trace

using Hsu.Formats.Asc;
using Hsu.Formats.Replay;

var parser = new AscParser();
var plan = await ReplayPlanBuilder.BuildAsync(
    parser,
    () => File.OpenRead("log.asc"));

using var transport = new UdpReplayTransport(new ReplayTarget("127.0.0.1", 5005));
using var session = new ReplaySession(plan, transport) { Speed = 1.0, Loop = false };

session.Progress += (_, e) => Console.WriteLine($"{e.SentCount}/{e.TotalCount}");
await session.RunAsync();

Replay an Ethernet capture

using Hsu.Formats.Pcapng;
using Hsu.Formats.Replay;

var parser = new PcapngParser();
var plan = await ReplayPlanBuilder.BuildAsync(
    parser,
    () => File.OpenRead("capture.pcapng"));

using var transport = new UdpReplayTransport(new ReplayTarget("239.1.2.3", 5005));
using var session = new ReplaySession(plan, transport)
{
    Speed = 1.0,
    Loop = false,
};

await session.RunAsync();

Replay from the CLI

ReplayTool cli --input capture.pcapng --host 127.0.0.1 --port 5005 --mode unicast
ReplayTool cli --input trace.asc --host 127.0.0.1 --port 5005 --compare --echo --builtin-responder

Timing Behavior

ReplaySession computes deterministic cumulative offsets from the source timestamps and uses one Stopwatch baseline for the active run.

Important behaviors:

• Speed < 1.0 slows replay down
• Speed > 1.0 speeds replay up
• Pause() / Resume() stop and restart the timing clock
• MaxIdleGap compresses long quiet periods without changing relative ordering
• Loop = true restarts the plan after the last item

Comparison / Duplex Workflows

The replay subsystem also supports expected-vs-live response comparison.

Key pieces:

• ReplayComparator
• IResponseDecoder
• IResponseCorrelator
• CompareOptions
• UdpDuplexTransport
• TcpDuplexTransport

Typical workflow:

1. build a replay plan from the recorded source
2. capture expected response units from the recording
3. replay over a duplex transport
4. feed live responses into ReplayComparator
5. build a ReplayComparisonReport

Encapsulation Model

Replay payload generation depends on the source event type:

• CAN trace frames are encapsulated through CanOverEthernetEncapsulator
• Ethernet capture packets are encapsulated through EthernetOverUdpEncapsulator
• both payload families share the same replay protocol prefix and carry a typed message kind
• CAN and Ethernet keep type-specific payload layouts while still belonging to one replay payload protocol family
• mixed ASC/BLF event streams can produce both kinds of replay items in timestamp order

Documentation

• Replay subsystem architecture and Ethernet capture design notes are documented in the project repository.
• Standard format specifications, when present, are documented in the project repository.

Related Tests

Additional replay examples and validation scenarios are available in the project test suite.