cscore: Change impl to only one singleton (#1398)

This avoids a number of shutdown use-after-free races by controlling the
destruction order.  It also is a prerequisite to making the internal
interfaces mockable for unit testing.

cscore/src/main/native/cpp/Instance.cpp

@@ -0,0 +1,64 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2016-2018 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "Instance.h"
+
+#include <wpi/Path.h>
+#include <wpi/SmallString.h>
+#include <wpi/StringRef.h>
+#include <wpi/raw_ostream.h>
+
+using namespace cs;
+
+static void def_log_func(unsigned int level, const char* file,
+                         unsigned int line, const char* msg) {
+  wpi::SmallString<128> buf;
+  wpi::raw_svector_ostream oss(buf);
+  if (level == 20) {
+    oss << "CS: " << msg << '\n';
+    wpi::errs() << oss.str();
+    return;
+  }
+
+  wpi::StringRef levelmsg;
+  if (level >= 50)
+    levelmsg = "CRITICAL: ";
+  else if (level >= 40)
+    levelmsg = "ERROR: ";
+  else if (level >= 30)
+    levelmsg = "WARNING: ";
+  else
+    return;
+  oss << "CS: " << levelmsg << msg << " (" << wpi::sys::path::filename(file)
+      << ':' << line << ")\n";
+  wpi::errs() << oss.str();
+}
+
+Instance::Instance() : telemetry(notifier), network_listener(logger, notifier) {
+  SetDefaultLogger();
+}
+
+Instance::~Instance() {}
+
+Instance& Instance::GetInstance() {
+  static Instance inst;
+  return inst;
+}
+
+void Instance::SetDefaultLogger() { logger.SetLogger(def_log_func); }
+
+std::pair<CS_Source, std::shared_ptr<SourceData>> Instance::FindSource(
+    const SourceImpl& source) {
+  return sources.FindIf(
+      [&](const SourceData& data) { return data.source.get() == &source; });
+}
+
+std::pair<CS_Sink, std::shared_ptr<SinkData>> Instance::FindSink(
+    const SinkImpl& sink) {
+  return sinks.FindIf(
+      [&](const SinkData& data) { return data.sink.get() == &sink; });
+}