Telemetry

You can read live car and session state through typed structs, or turn on a shared-memory feed for external tools. Each read gives you the most recent frame.

Header	swofty/telemetry.hpp
Namespace	swofty::telemetry
Table	SwoftyApi::telemetry (SwoftyTelemetry)
Feature	telemetry — experimental, off by default
API version	5
Thread	Flow thread

Every call returns swofty::telemetry::Result (ok, late, unavailable, invalid). To see what each means, read the result codes.

Calls

Call	Returns
available()	true when the feature is on, implemented, and a session is live
session(out)	ok and fills SwoftySessionState; unavailable outside a session
car(index, out)	ok and fills SwoftyCarState; invalid for an out-of-range index
participant(index, out)	ok and fills SwoftyParticipant
shared_memory(&name)	turns the shared feed on and writes the mapping name

To read a particular participant, pass their participant index as index. For your player's index, use SwoftySessionState::player_index. The structs carry version = SWOFTY_TELEMETRY_VERSION (1). Each ends in a reserved block so fields can be added without changing the struct's size.

• SwoftyCarState — speed (m/s), rpm, gear, throttle/brake/clutch/steer, per-wheel tyre temp, tyre wear and brake temp, fuel, position, lap, sector, lap and sector times, lap distance, world position and velocity.
• SwoftySessionState — session type, track, flag, weather, total laps, participant count, player index, session time, time left, track and air temperature.
• SwoftyParticipant — name, team, position, lap, lap distance, best lap time.

Example

To log your player's speed every frame, read the session first: it gives you the index to use for the car read.

#include <swofty/events.hpp>
#include <swofty/telemetry.hpp>

namespace tel = swofty::telemetry;

static void frame(double, void *)
{
    if (!tel::available())
        return;
    tel::SessionState s{};
    tel::CarState car{};
    if (tel::session(&s) == tel::Result::ok && tel::car(s.player_index, &car) == tel::Result::ok)
        swofty::log("[my-addon] %.0f km/h, gear %d", car.speed * 3.6f, car.gear);
}

SWOFTY_ON_LOAD
{
    swofty::events::on_frame(frame);
}

SWOFTY_ADDON()

Name your plugin in operations.native:

"operations": {
  "native": [{ "dll": "native/my_plugin.dll" }]
}

Shared-memory feed

To turn on the feed for external tools, call shared_memory(&name). It opens a named file mapping (Local\SwoftyTelemetry) and writes its name. Inside the mapping is a SwoftyTelemetryFeed:

Field	Type	Notes
version	uint32	SWOFTY_TELEMETRY_VERSION
size	uint32	sizeof(SwoftyTelemetryFeed)
seq	uint64	seqlock; odd while a frame is being written
frame	uint64	frame counter
session	SwoftySessionState	current session
cars	SwoftyCarState[24]	per participant
participants	SwoftyParticipant[24]	per participant

Use the sequence counter to check whether a frame was written while you were copying the data:

1. Check that seq is even.
2. Copy the fields you need.
3. Check that seq hasn't changed. If it has, retry.

The name stays valid for the lifetime of the process.

Availability

telemetry is experimental, and experimental_features in a manifest doesn't accept it yet; see feature gates. The telemetry engine lane hasn't landed yet, so every call on current builds returns unavailable. See the native-libraries design.