Initial commit of cross connect integration test project (#3434)

Adding as a separate project so current integration tests stay working.

crossConnIntegrationTests/src/main/native/cpp/mockds/MockDS.cpp

@@ -0,0 +1,86 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "MockDS.h"
+
+#include <stdint.h>
+
+#include <string_view>
+
+#include <fmt/core.h>
+#include <hal/cpp/fpga_clock.h>
+#include <wpi/Logger.h>
+#include <wpi/SmallVector.h>
+#include <wpi/UDPClient.h>
+
+static void LoggerFunc(unsigned int level, const char* file, unsigned int line,
+                       const char* msg) {
+  if (level == 20) {
+    fmt::print(stderr, "DS: {}\n", msg);
+    return;
+  }
+
+  std::string_view levelmsg;
+  if (level >= 50) {
+    levelmsg = "CRITICAL";
+  } else if (level >= 40) {
+    levelmsg = "ERROR";
+  } else if (level >= 30) {
+    levelmsg = "WARNING";
+  } else {
+    return;
+  }
+  fmt::print(stderr, "DS: {}: {} ({}:{})\n", levelmsg, msg, file, line);
+}
+
+static void generateEnabledDsPacket(wpi::SmallVectorImpl<uint8_t>& data,
+                                    uint16_t sendCount) {
+  data.clear();
+  data.push_back(sendCount >> 8);
+  data.push_back(sendCount);
+  data.push_back(0x01);  // general data tag
+  data.push_back(0x04);  // teleop enabled
+  data.push_back(0x10);  // normal data request
+  data.push_back(0x00);  // red 1 station
+}
+
+void MockDS::Start() {
+  if (m_active) {
+    return;
+  }
+  m_active = true;
+  m_thread = std::thread([&]() {
+    wpi::Logger logger(LoggerFunc);
+    wpi::UDPClient client(logger);
+    client.start();
+    auto timeout_time = hal::fpga_clock::now();
+    int initCount = 0;
+    uint16_t sendCount = 0;
+    wpi::SmallVector<uint8_t, 8> data;
+    while (m_active) {
+      // Keep 20ms intervals, and increase time to next interval
+      auto current = hal::fpga_clock::now();
+      while (timeout_time <= current) {
+        timeout_time += std::chrono::milliseconds(20);
+      }
+      std::this_thread::sleep_until(timeout_time);
+      generateEnabledDsPacket(data, sendCount++);
+      // ~10 disabled packets are required to make the robot actually enable
+      // 1 is definitely not enough.
+      if (initCount < 10) {
+        initCount++;
+        data[3] = 0;
+      }
+      client.send(data, "127.0.0.1", 1110);
+    }
+    client.shutdown();
+  });
+}
+
+void MockDS::Stop() {
+  m_active = false;
+  if (m_thread.joinable()) {
+    m_thread.join();
+  }
+}