[wpiutil, wpilib] Add FileLogger and log console output (#6977)

wpiutil/src/test/native/cpp/FileLoggerTest.cpp

@@ -0,0 +1,52 @@
+// 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 <string_view>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include "wpi/FileLogger.h"
+
+TEST(FileLoggerTest, LineBufferSingleLine) {
+  std::vector<std::string> buf;
+  auto func = wpi::FileLogger::LineBuffer(
+      [&buf](std::string_view line) { buf.emplace_back(line); });
+  func("qwertyuiop\n");
+  EXPECT_EQ(buf.front(), "qwertyuiop");
+  buf.clear();
+}
+
+TEST(FileLoggerTest, LineBufferMultiLine) {
+  std::vector<std::string> buf;
+  auto func = wpi::FileLogger::LineBuffer(
+      [&buf](std::string_view line) { buf.emplace_back(line); });
+  func("line 1\nline 2\nline 3\n");
+  EXPECT_EQ("line 1", buf[0]);
+  EXPECT_EQ("line 2", buf[1]);
+  EXPECT_EQ("line 3", buf[2]);
+}
+
+TEST(FileLoggerTest, LineBufferPartials) {
+  std::vector<std::string> buf;
+  auto func = wpi::FileLogger::LineBuffer(
+      [&buf](std::string_view line) { buf.emplace_back(line); });
+  func("part 1");
+  func("part 2\npart 3");
+  EXPECT_EQ("part 1part 2", buf.front());
+  buf.clear();
+  func("\n");
+  EXPECT_EQ("part 3", buf.front());
+}
+
+TEST(FileLoggerTest, LineBufferMultiplePartials) {
+  std::vector<std::string> buf;
+  auto func = wpi::FileLogger::LineBuffer(
+      [&buf](std::string_view line) { buf.emplace_back(line); });
+  func("part 1");
+  func("part 2");
+  func("part 3");
+  func("part 4\n");
+  EXPECT_EQ("part 1part 2part 3part 4", buf.front());
+}