Add JSON support for Trajectories (#2025)

wpilibc/src/main/native/cpp/trajectory/TrajectoryUtil.cpp

@@ -0,0 +1,58 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 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 "frc/trajectory/TrajectoryUtil.h"
+
+#include <system_error>
+
+#include <wpi/SmallString.h>
+#include <wpi/json.h>
+#include <wpi/raw_istream.h>
+#include <wpi/raw_ostream.h>
+
+using namespace frc;
+
+void TrajectoryUtil::ToPathweaverJson(const Trajectory& trajectory,
+                                      const wpi::Twine& path) {
+  std::error_code error_code;
+
+  wpi::SmallString<128> buf;
+  wpi::raw_fd_ostream output{path.toStringRef(buf), error_code};
+  if (error_code) {
+    throw std::runtime_error(("Cannot open file: " + path).str());
+  }
+
+  wpi::json json = trajectory.States();
+  output << json;
+  output.flush();
+}
+
+Trajectory TrajectoryUtil::FromPathweaverJson(const wpi::Twine& path) {
+  std::error_code error_code;
+
+  wpi::SmallString<128> buf;
+  wpi::raw_fd_istream input{path.toStringRef(buf), error_code};
+  if (error_code) {
+    throw std::runtime_error(("Cannot open file: " + path).str());
+  }
+
+  wpi::json json;
+  input >> json;
+
+  return Trajectory{json.get<std::vector<Trajectory::State>>()};
+}
+
+std::string TrajectoryUtil::SerializeTrajectory(const Trajectory& trajectory) {
+  wpi::json json = trajectory.States();
+  return json.dump();
+}
+
+Trajectory TrajectoryUtil::DeserializeTrajectory(
+    const wpi::StringRef json_str) {
+  wpi::json json = wpi::json::parse(json_str);
+  return Trajectory{json.get<std::vector<Trajectory::State>>()};
+}