flatudp: the source, kind, mock sender and stream probes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/source/flatudp/flatudp_kind.cpp

@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2026 Martino Ferrari
+
+#include "source/flatudp/flatudp_source.hpp"
+#include "source/registry.hpp"
+
+#include <adwaita.h>
+
+#include <cstdio>
+#include <functional>
+#include <memory>
+#include <string>
+
+namespace udpscope {
+namespace {
+
+using namespace flatudp;
+using ChangeCb = std::shared_ptr<std::function<void()>>;
+
+std::string num(double v) {
+  char b[48];
+  std::snprintf(b, sizeof b, "%.10g", v);
+  return b;
+}
+
+GtkWidget* entry_row(const char* title) {
+  GtkWidget* r = adw_entry_row_new();
+  adw_preferences_row_set_title(ADW_PREFERENCES_ROW(r), title);
+  adw_preferences_row_set_use_underline(ADW_PREFERENCES_ROW(r), TRUE);
+  return r;
+}
+
+GtkWidget* spin_row(const char* title, double lo, double hi, double step, double def, int digits) {
+  GtkWidget* r = GTK_WIDGET(adw_spin_row_new_with_range(lo, hi, step));
+  adw_preferences_row_set_title(ADW_PREFERENCES_ROW(r), title);
+  adw_preferences_row_set_use_underline(ADW_PREFERENCES_ROW(r), TRUE);
+  adw_spin_row_set_digits(ADW_SPIN_ROW(r), static_cast<guint>(digits));
+  adw_spin_row_set_value(ADW_SPIN_ROW(r), def);
+  return r;
+}
+
+GtkWidget* combo_row(const char* title, const char* const* items) {
+  GtkWidget* r = adw_combo_row_new();
+  adw_preferences_row_set_title(ADW_PREFERENCES_ROW(r), title);
+  adw_preferences_row_set_use_underline(ADW_PREFERENCES_ROW(r), TRUE);
+  adw_combo_row_set_model(ADW_COMBO_ROW(r), G_LIST_MODEL(gtk_string_list_new(items)));
+  return r;
+}
+
+GtkWidget* expander(const char* title, std::initializer_list<GtkWidget*> rows) {
+  GtkWidget* e = adw_expander_row_new();
+  adw_preferences_row_set_title(ADW_PREFERENCES_ROW(e), title);
+  for (GtkWidget* r : rows) adw_expander_row_add_row(ADW_EXPANDER_ROW(e), r);
+  return e;
+}
+
+std::string text_of(GtkWidget* w) { return gtk_editable_get_text(GTK_EDITABLE(w)); }
+double value_of(GtkWidget* w) { return adw_spin_row_get_value(ADW_SPIN_ROW(w)); }
+guint sel_of(GtkWidget* w) { return adw_combo_row_get_selected(ADW_COMBO_ROW(w)); }
+
+void mark(GtkWidget* w, bool bad) {
+  if (bad) {
+    gtk_widget_add_css_class(w, "error");
+  } else {
+    gtk_widget_remove_css_class(w, "error");
+  }
+}
+
+/// The form's widgets, shared by every signal closure and every `ConfigForm` closure.
+struct Form {
+  GtkWidget *port, *bind, *multicast, *iface, *rate, *endian, *signals;
+  ChangeCb changed = std::make_shared<std::function<void()>>();
+  bool updating = false;
+  bool alive = true;  ///< cleared when the chooser destroys the rows; handlers then touch nothing
+
+  /// A bad address is marked with the `error` style; the rest of the problem is `valid()`'s.
+  void refresh() {
+    mark(bind, !text_of(bind).empty() && !valid_ipv4(text_of(bind)));
+    mark(multicast, !text_of(multicast).empty() && !valid_multicast(text_of(multicast)));
+    mark(iface, !text_of(iface).empty() && !valid_ipv4(text_of(iface)));
+  }
+
+  SourceConfig read() const {
+    SourceConfig c;
+    c.set("port", num(value_of(port)));
+    if (!text_of(bind).empty()) c.set("bind", text_of(bind));
+    if (!text_of(multicast).empty()) c.set("multicast", text_of(multicast));
+    if (!text_of(iface).empty()) c.set("iface", text_of(iface));
+    c.set("rate", num(value_of(rate)));
+    c.set("endian", sel_of(endian) == 1 ? "big" : "little");
+    c.set("signals", text_of(signals));
+    return c;
+  }
+
+  void write(const SourceConfig& cfg) {
+    const FlatUdpSettings s = FlatUdpSettings::from(cfg);
+    updating = true;
+    adw_spin_row_set_value(ADW_SPIN_ROW(port), s.port);
+    gtk_editable_set_text(GTK_EDITABLE(bind), s.bind.c_str());
+    gtk_editable_set_text(GTK_EDITABLE(multicast), s.multicast.c_str());
+    gtk_editable_set_text(GTK_EDITABLE(iface), s.iface.c_str());
+    if (s.rate > 0.0) adw_spin_row_set_value(ADW_SPIN_ROW(rate), s.rate);
+    adw_combo_row_set_selected(ADW_COMBO_ROW(endian), s.big_endian ? 1 : 0);
+    gtk_editable_set_text(GTK_EDITABLE(signals), cfg.get("signals").c_str());
+    updating = false;
+    refresh();
+  }
+
+  bool valid() const { return FlatUdpSettings::from(read()).problem().empty(); }
+};
+
+using FormPtr = std::shared_ptr<Form>;
+
+void on_notify(GObject*, GParamSpec*, gpointer user) {
+  Form& f = **static_cast<FormPtr*>(user);
+  if (!f.alive) return;
+  f.refresh();
+  if (!f.updating && f.changed && *f.changed) (*f.changed)();
+}
+
+void on_edited(GtkEditable*, gpointer user) {
+  Form& f = **static_cast<FormPtr*>(user);
+  if (!f.alive) return;
+  f.refresh();
+  if (!f.updating && f.changed && *f.changed) (*f.changed)();
+}
+
+void free_form(gpointer d, GClosure*) { delete static_cast<FormPtr*>(d); }
+
+/// "destroy" on a row group: the siblings the handlers reach by raw pointer may already be gone.
+void on_form_destroy(GtkWidget*, gpointer user) { (**static_cast<FormPtr*>(user)).alive = false; }
+
+void hook_destroy(GtkWidget* w, const FormPtr& f) {
+  g_signal_connect_data(w, "destroy", G_CALLBACK(on_form_destroy), new FormPtr(f), free_form,
+                        static_cast<GConnectFlags>(0));
+}
+
+void hook_notify(GtkWidget* w, const char* signal, const FormPtr& f) {
+  g_signal_connect_data(w, signal, G_CALLBACK(on_notify), new FormPtr(f), free_form,
+                        static_cast<GConnectFlags>(0));
+}
+
+void hook_entry(GtkWidget* w, const FormPtr& f) {
+  g_signal_connect_data(w, "changed", G_CALLBACK(on_edited), new FormPtr(f), free_form,
+                        static_cast<GConnectFlags>(0));
+}
+
+class FlatUdpKind final : public SourceKind {
+ public:
+  std::string id() const override { return "flatudp"; }
+  std::string display_name() const override { return "Flat UDP (MARTe2 UDPSender)"; }
+  bool has_datagrams() const override { return true; }
+
+  std::string identity(const SourceConfig& cfg) const override {
+    return FlatUdpSettings::from(cfg).identity();
+  }
+
+  std::unique_ptr<DataSource> make(const SourceConfig& cfg) const override {
+    return std::make_unique<FlatUdpSource>(cfg);
+  }
+
+  ConfigForm make_config_form() const override {
+    auto f = std::make_shared<Form>();
+    static const char* const kEndian[] = {"Little endian", "Big endian", nullptr};
+
+    f->port = spin_row("_Port", 1, 65535, 1, kDefaultPort, 0);
+    f->bind = entry_row("_Bind address");
+    f->multicast = entry_row("_Multicast group");
+    f->iface = entry_row("Multicast _interface");
+    f->rate = spin_row("Cycle _rate (Hz)", 0.001, 1000000, 1, 1000, 3);
+    f->endian = combo_row("_Byte order", kEndian);
+    f->signals = entry_row("_Signals");
+
+    GtkWidget* net = expander("Network", {f->port, f->bind, f->multicast, f->iface});
+    GtkWidget* timing = expander("Timing and format", {f->rate, f->endian});
+    GtkWidget* sig = expander("Signals", {f->signals});
+    adw_expander_row_set_expanded(ADW_EXPANDER_ROW(net), TRUE);
+    adw_expander_row_set_expanded(ADW_EXPANDER_ROW(sig), TRUE);
+
+    for (GtkWidget* w : {net, timing, sig}) hook_destroy(w, f);
+    for (GtkWidget* w : {f->bind, f->multicast, f->iface, f->signals}) hook_entry(w, f);
+    for (GtkWidget* w : {f->port, f->rate}) hook_notify(w, "notify::value", f);
+    hook_notify(f->endian, "notify::selected", f);
+    f->refresh();
+
+    ConfigForm out;
+    out.rows = {net, timing, sig};
+    out.description =
+        "The signal list must match the sender's exactly, in order: the datagrams carry no "
+        "description. Write name:type[count], comma separated, e.g. Trigger:uint8,Ia:float32,"
+        "Wave:float32[16]";
+    out.focus = f->signals;
+    out.write = [f](const SourceConfig& c) { f->write(c); };
+    out.read = [f]() { return f->read(); };
+    out.valid = [f]() { return f->valid(); };
+    ChangeCb cb = f->changed;
+    out.on_change = [cb](std::function<void()> fn) { *cb = std::move(fn); };
+    return out;
+  }
+};
+
+}  // namespace
+
+std::unique_ptr<SourceKind> make_flatudp_kind() { return std::make_unique<FlatUdpKind>(); }
+
+}  // namespace udpscope

src/source/flatudp/flatudp_source.cpp

@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2026 Martino Ferrari
+
+#include "source/flatudp/flatudp_source.hpp"
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <poll.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <cctype>
+#include <cerrno>
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+#include <stdexcept>
+#include <thread>
+
+namespace udpscope::flatudp {
+namespace {
+
+using namespace std::chrono_literals;
+
+std::string lower(std::string s) {
+  for (char& c : s) c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+  return s;
+}
+
+std::string trim(const std::string& s) {
+  std::size_t a = 0, b = s.size();
+  while (a < b && std::isspace(static_cast<unsigned char>(s[a]))) ++a;
+  while (b > a && std::isspace(static_cast<unsigned char>(s[b - 1]))) --b;
+  return s.substr(a, b - a);
+}
+
+double epoch_seconds() {
+  return std::chrono::duration<double>(std::chrono::system_clock::now().time_since_epoch()).count();
+}
+
+constexpr std::size_t kMaxReportedSizes = 8;  ///< a sender of random sizes must not flood stderr
+
+}  // namespace
+
+bool valid_ipv4(const std::string& s) {
+  in_addr a{};
+  return inet_pton(AF_INET, s.c_str(), &a) == 1;
+}
+
+bool valid_multicast(const std::string& s) {
+  in_addr a{};
+  if (inet_pton(AF_INET, s.c_str(), &a) != 1) return false;
+  return (ntohl(a.s_addr) >> 28) == 0xE;
+}
+
+// --- FlatUdpSettings ------------------------------------------------------------------------
+
+FlatUdpSettings FlatUdpSettings::from(const SourceConfig& c) {
+  FlatUdpSettings s;
+  s.port = static_cast<int>(c.get_int("port", kDefaultPort));
+  s.bind = trim(c.get("bind"));
+  s.multicast = trim(c.get("multicast"));
+  s.iface = trim(c.get("iface"));
+  s.rate = c.get_double("rate", 0.0);
+  const std::string e = lower(trim(c.get("endian", "little")));
+  s.endian_ok = e == "little" || e == "big";
+  s.big_endian = e == "big";
+  s.signals_error = parse(c.get("signals"), s.rows);
+  return s;
+}
+
+std::string FlatUdpSettings::problem() const {
+  if (port < 1 || port > 65535) return "the port must be 1 to 65535";
+  if (!signals_error.empty()) return signals_error;
+  const std::string p = flatudp::problem(rows);
+  if (!p.empty()) return p;
+  if (!(rate > 0.0) || !std::isfinite(rate)) return "give the sender's cycle rate in Hz (rate)";
+  if (!endian_ok) return "endian must be little or big";
+  if (!bind.empty() && !valid_ipv4(bind)) return "the bind address '" + bind + "' is not an IPv4 address";
+  if (!multicast.empty() && !valid_multicast(multicast))
+    return "'" + multicast + "' is not a multicast group (224.0.0.0 to 239.255.255.255)";
+  if (!iface.empty() && !valid_ipv4(iface))
+    return "the interface address '" + iface + "' is not an IPv4 address";
+  return {};
+}
+
+std::string FlatUdpSettings::identity() const {
+  return (multicast.empty() ? std::string() : multicast + ":") + std::to_string(port);
+}
+
+std::size_t FlatUdpSettings::block() const {
+  if (!all_scalar(rows) || !(rate > 0.0) || !std::isfinite(rate)) return 1;
+  const long b = std::lround(rate / 100.0);
+  return static_cast<std::size_t>(std::min(1024L, std::max(1L, b)));
+}
+
+// --- FlatUdpSource --------------------------------------------------------------------------
+
+FlatUdpSource::FlatUdpSource(const SourceConfig& cfg) : cfg_(FlatUdpSettings::from(cfg)) {}
+
+FlatUdpSource::~FlatUdpSource() { close_fd(); }
+
+std::string FlatUdpSource::last_message() const {
+  std::lock_guard<std::mutex> lk(msg_mu_);
+  return last_message_;
+}
+
+void FlatUdpSource::note(const std::string& msg) {
+  {
+    std::lock_guard<std::mutex> lk(msg_mu_);
+    last_message_ = msg;
+  }
+  std::fprintf(stderr, "[flatudp] %s\n", msg.c_str());
+  std::fflush(stderr);
+}
+
+void FlatUdpSource::close_fd() {
+  if (fd_ >= 0) {
+    ::close(fd_);
+    fd_ = -1;
+  }
+}
+
+void FlatUdpSource::open(SourceSink& sink) {
+  const std::string p = cfg_.problem();
+  if (!p.empty()) throw std::runtime_error(p);
+  sink_ = &sink;
+
+  signals_.clear();
+  for (const Row& r : cfg_.rows) {
+    SignalInfo s;
+    s.name = r.name;
+    s.type_code = static_cast<std::uint8_t>(r.type);
+    s.rows = r.count;
+    s.cols = 1;
+    s.time_mode = kTimePacket;
+    s.sampling_rate = cfg_.rate;
+    signals_.push_back(s);
+  }
+  expected_ = datagram_size(cfg_.rows);
+  block_ = cfg_.block();
+  pending_.assign(cfg_.rows.size(), {});
+  pending_n_ = 0;
+  rx_.assign(65536, 0);
+
+  const auto fail = [this](const std::string& what) {
+    const std::string msg = what + ": " + std::strerror(errno);
+    close_fd();
+    throw std::runtime_error(msg);
+  };
+
+  fd_ = ::socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+  if (fd_ < 0) fail("cannot create a UDP socket");
+  // Receivers of one multicast group share its port; a unicast port is the one app's.
+  if (!cfg_.multicast.empty()) {
+    const int one = 1;
+    ::setsockopt(fd_, SOL_SOCKET, SO_REUSEADDR, &one, sizeof one);
+  }
+  const int rcvbuf = 4 << 20;  // best effort: a 1 kHz sender at 64 KiB would not fit a default one
+  ::setsockopt(fd_, SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof rcvbuf);
+
+  sockaddr_in addr{};
+  addr.sin_family = AF_INET;
+  addr.sin_port = htons(static_cast<std::uint16_t>(cfg_.port));
+  addr.sin_addr.s_addr = htonl(INADDR_ANY);
+  if (!cfg_.bind.empty()) inet_pton(AF_INET, cfg_.bind.c_str(), &addr.sin_addr);
+  if (::bind(fd_, reinterpret_cast<const sockaddr*>(&addr), sizeof addr) < 0)
+    fail("cannot bind UDP port " + std::to_string(cfg_.port));
+
+  if (!cfg_.multicast.empty()) {
+    ip_mreq mreq{};
+    inet_pton(AF_INET, cfg_.multicast.c_str(), &mreq.imr_multiaddr);
+    if (cfg_.iface.empty()) {
+      mreq.imr_interface.s_addr = htonl(INADDR_ANY);
+    } else {
+      inet_pton(AF_INET, cfg_.iface.c_str(), &mreq.imr_interface);
+    }
+    if (::setsockopt(fd_, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof mreq) < 0)
+      fail("cannot join multicast group " + cfg_.multicast);
+  }
+}
+
+void FlatUdpSource::close() {
+  close_fd();
+  connected_.store(false, std::memory_order_relaxed);
+}
+
+SourceStats FlatUdpSource::stats() const {
+  SourceStats s;
+  s.packets = valid_.load(std::memory_order_relaxed) + wrong_.load(std::memory_order_relaxed);
+  s.frames = frames_;
+  s.stale = wrong_.load(std::memory_order_relaxed);
+  s.reconnects = reconnects_;
+  s.connected = connected_.load(std::memory_order_relaxed);
+  return s;
+}
+
+void FlatUdpSource::poll(int timeout_ms) {
+  drain_commands();
+  // Never wait long: the partial-block flush and the silence timeout are checked on this cadence.
+  const int wait = std::clamp(timeout_ms, 0, 20);
+  if (fd_ < 0 || sink_ == nullptr) {
+    std::this_thread::sleep_for(std::chrono::milliseconds(wait));
+    return;
+  }
+  if (!configured_) {
+    configured_ = true;
+    sink_->on_config(signals_, 1);
+  }
+  pollfd p{};
+  p.fd = fd_;
+  p.events = POLLIN;
+  if (::poll(&p, 1, wait) > 0 && (p.revents & POLLIN)) drain_socket();
+
+  const auto now = Clock::now();
+  if (pending_n_ > 0 && now - batch_start_ >= 100ms) flush();  // a stopped sender holds nothing back
+  if (connected_.load(std::memory_order_relaxed) && now - last_valid_ >= 2s) {
+    connected_.store(false, std::memory_order_relaxed);
+    sink_->on_event(SourceEvent::Disconnected, "no datagram for 2 s");
+  }
+}
+
+void FlatUdpSource::drain_socket() {
+  for (int i = 0; i < 8192; ++i) {  // bounded, so a flood cannot starve the timers
+    const ssize_t n = ::recv(fd_, rx_.data(), rx_.size(), 0);
+    if (n < 0) {
+      if (errno == EINTR) continue;
+      break;  // EAGAIN: drained
+    }
+    const double t = epoch_seconds();
+    const std::size_t len = static_cast<std::size_t>(n);
+    if (tap_) tap_(rx_.data(), len, t);
+    if (len == expected_) {
+      accept(rx_.data());
+    } else {
+      reject(len);
+    }
+  }
+}
+
+void FlatUdpSource::accept(const std::uint8_t* data) {
+  valid_.fetch_add(1, std::memory_order_relaxed);
+  last_valid_ = Clock::now();
+  if (!connected_.load(std::memory_order_relaxed)) {
+    if (ever_connected_) ++reconnects_;
+    ever_connected_ = true;
+    connected_.store(true, std::memory_order_relaxed);
+    sink_->on_event(SourceEvent::Connected, "");
+  }
+  decode_datagram(cfg_.rows, data, cfg_.big_endian, pending_);
+  if (pending_n_ == 0) batch_start_ = last_valid_;
+  if (++pending_n_ >= block_) flush();
+}
+
+void FlatUdpSource::reject(std::size_t len) {
+  wrong_.fetch_add(1, std::memory_order_relaxed);
+  if (reported_sizes_.size() >= kMaxReportedSizes || !reported_sizes_.insert(len).second) return;
+  const std::string msg = "datagram of " + std::to_string(len) + " bytes, expected " +
+                          std::to_string(expected_) + ", check the signal list";
+  note(msg);
+  sink_->on_event(SourceEvent::Error, msg.c_str());
+}
+
+void FlatUdpSource::flush() {
+  const std::size_t n = signals_.size();
+  views_.resize(n);
+  for (std::size_t i = 0; i < n; ++i)
+    views_[i] = SignalValues{pending_[i].data(), static_cast<std::uint32_t>(pending_[i].size())};
+  Frame f;
+  f.counter = frame_counter_++;
+  f.lost = 0;
+  f.late = false;
+  f.recv_time = epoch_seconds();
+  f.publish_mode = 1;
+  f.num_samples = static_cast<std::uint32_t>(pending_n_);
+  f.num_signals = static_cast<std::uint32_t>(n);
+  f.signals = signals_.data();
+  f.values = views_.data();
+  ++frames_;
+  sink_->on_data(f);
+  for (auto& c : pending_) c.clear();
+  pending_n_ = 0;
+}
+
+}  // namespace udpscope::flatudp

src/source/flatudp/flatudp_source.hpp

@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2026 Martino Ferrari
+
+#pragma once
+
+#include "source/data_source.hpp"
+#include "source/flatudp/flatudp_signals.hpp"
+#include "source/source_config.hpp"
+
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <mutex>
+#include <set>
+#include <string>
+#include <vector>
+
+namespace udpscope::flatudp {
+
+constexpr int kDefaultPort = 44488;  ///< `UDPSender`'s own default
+
+bool valid_ipv4(const std::string& s);
+/// An IPv4 address in 224.0.0.0/4.
+bool valid_multicast(const std::string& s);
+
+/// Everything a configured flat UDP source needs, parsed once from the flat `SourceConfig`.
+struct FlatUdpSettings {
+  int port = kDefaultPort;
+  std::string bind;       ///< local address; empty is any
+  std::string multicast;  ///< group to join; empty is plain unicast
+  std::string iface;      ///< local interface address for the join; empty is the system's choice
+  double rate = 0.0;      ///< the sender's cycle rate in Hz; 0 means not given
+  bool big_endian = false;
+  bool endian_ok = true;  ///< false when `endian` is neither "little" nor "big"
+  std::vector<Row> rows;
+  std::string signals_error;  ///< why the `signals` text did not parse; `rows` is empty then
+
+  static FlatUdpSettings from(const SourceConfig& cfg);
+  /// The first reason this cannot connect, in words for the user; empty when it can.
+  std::string problem() const;
+  /// `[multicast:]port`; names the session file.
+  std::string identity() const;
+  /// Datagrams per frame: 1 for a list with a vector, else `clamp(round(rate / 100), 1, 1024)`.
+  std::size_t block() const;
+};
+
+class FlatUdpSource final : public DataSource {
+ public:
+  explicit FlatUdpSource(const SourceConfig& cfg);
+  ~FlatUdpSource() override;
+
+  void open(SourceSink& sink) override;
+  void poll(int timeout_ms) override;
+  void close() override;
+  SourceStats stats() const override;
+  bool connected() const override { return connected_.load(std::memory_order_relaxed); }
+  void set_datagram_tap(DatagramTap tap) override { tap_ = std::move(tap); }
+
+  const FlatUdpSettings& settings() const { return cfg_; }
+  /// Datagrams of the expected size / of any other size; for the probe, readable from any thread.
+  std::uint64_t valid_datagrams() const { return valid_.load(std::memory_order_relaxed); }
+  std::uint64_t wrong_size_datagrams() const { return wrong_.load(std::memory_order_relaxed); }
+  std::string last_message() const;
+
+ private:
+  using Clock = std::chrono::steady_clock;
+
+  void close_fd();
+  void drain_socket();
+  void accept(const std::uint8_t* data);
+  void reject(std::size_t len);
+  void flush();
+  void note(const std::string& msg);
+
+  FlatUdpSettings cfg_;
+  SourceSink* sink_ = nullptr;
+  DatagramTap tap_;
+  int fd_ = -1;
+  bool configured_ = false;
+  bool ever_connected_ = false;
+  std::size_t expected_ = 0;  ///< bytes of a valid datagram
+  std::size_t block_ = 1;
+
+  std::vector<SignalInfo> signals_;
+  std::vector<std::uint8_t> rx_;
+  std::vector<std::vector<double>> pending_;  ///< decoded, not yet framed: [signal][value]
+  std::vector<SignalValues> views_;
+  std::size_t pending_n_ = 0;  ///< datagrams in `pending_`
+  Clock::time_point batch_start_;
+  Clock::time_point last_valid_;
+  std::set<std::size_t> reported_sizes_;
+
+  std::atomic<bool> connected_{false};
+  std::atomic<std::uint64_t> valid_{0};
+  std::atomic<std::uint64_t> wrong_{0};
+  mutable std::mutex msg_mu_;
+  std::string last_message_;
+
+  std::uint32_t frame_counter_ = 0;
+  std::uint64_t frames_ = 0;
+  std::uint64_t reconnects_ = 0;
+};
+
+}  // namespace udpscope::flatudp

src/source/registry.cpp

@@ -51,6 +51,7 @@ void register_builtin_sources() {
   done = true;
   register_kind(make_udps_kind());
   register_kind(make_e1608_kind());
+  register_kind(make_flatudp_kind());
   if (std::getenv("UDPSCOPE_PROBE_SOURCE_KINDS") != nullptr) register_kind(make_probe_kind());
 }
 

src/source/registry.hpp

@@ -21,10 +21,11 @@ const std::vector<SourceKind*>& kinds();
 /// may drop. A later `dlopen` loader would only call `register_kind()`.
 void register_builtin_sources();
 
-/// The built-in kinds, each defined in its own file (`udps_kind.cpp`, `probe_source.cpp`, `e1608/e1608_kind.cpp`).
+/// The built-in kinds, each defined in its own file (`udps_kind.cpp`, `probe_source.cpp`, `e1608/e1608_kind.cpp`, `flatudp/flatudp_kind.cpp`).
 std::unique_ptr<SourceKind> make_udps_kind();
 std::unique_ptr<SourceKind> make_probe_kind();
 std::unique_ptr<SourceKind> make_e1608_kind();
+std::unique_ptr<SourceKind> make_flatudp_kind();
 
 /// The (host, port) pair that names a source's session file. UDPS keeps its legacy
 /// `server`/`port`; any other kind is `"<kind>-<identity>"` (characters outside `[A-Za-z0-9._-]`