Once files moved to aos folder and files updated accordingly

Change-Id: Idd26fca1d4dc15407e92859400e1a15a8a142ec3
diff --git a/aos/once_test.cc b/aos/once_test.cc
new file mode 100644
index 0000000..0a36643
--- /dev/null
+++ b/aos/once_test.cc
@@ -0,0 +1,130 @@
+#include "aos/once.h"
+
+#include <stdlib.h>
+#include <limits.h>
+
+#include "gtest/gtest.h"
+
+namespace aos {
+namespace testing {
+
+class OnceTest : public ::testing::Test {
+ public:
+  static int *Function() {
+    ++times_run_;
+    value_ = 971 + times_run_;
+    return &value_;
+  }
+
+ protected:
+  void SetUp() {
+    value_ = 0;
+    times_run_ = 0;
+  }
+
+  static int value_;
+  static int times_run_;
+};
+int OnceTest::value_, OnceTest::times_run_;
+
+// Makes sure that it calls the function at the right time and that it correctly
+// passes the result out.
+TEST_F(OnceTest, Works) {
+  static Once<int> once(Function);
+
+  EXPECT_EQ(0, value_);
+  EXPECT_EQ(0, times_run_);
+
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_NE(0, value_);
+  EXPECT_NE(0, times_run_);
+  // Make sure it's not passing it through an assignment by value or something
+  // else weird.
+  EXPECT_EQ(&value_, once.Get());
+}
+
+// Makes sure that having a Once at namespace scope works correctly.
+namespace {
+
+Once<int> global_once(OnceTest::Function);
+
+}  // namespace
+
+TEST_F(OnceTest, Global) {
+  EXPECT_EQ(value_, *global_once.Get());
+  EXPECT_NE(0, value_);
+  EXPECT_NE(0, times_run_);
+}
+
+// Makes sure that an instance keeps returning the same value without running
+// the function again.
+TEST_F(OnceTest, MultipleGets) {
+  static Once<int> once(Function);
+
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(1, times_run_);
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(1, times_run_);
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(1, times_run_);
+}
+
+// Tests to make sure that the right methods clear out the instance variables at
+// the right times.
+TEST_F(OnceTest, MemoryClearing) {
+  Once<int> once(NULL);
+
+  once.run_ = 1;
+  once.done_ = true;
+  // Run the constructor again to make sure it doesn't touch the variables set
+  // above.
+  new (&once)Once<int>(Function);
+
+  // Should return a random, (potentially) uninitialized value.
+  once.Get();
+  EXPECT_EQ(0, times_run_);
+
+  once.Reset();
+  EXPECT_EQ(0, times_run_);
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(1, times_run_);
+}
+
+namespace {
+
+int second_result = 0;
+int *SecondFunction() {
+  static int result = 254;
+  second_result = ++result;
+  return &second_result;
+}
+
+}  // namespace
+
+// Makes sure that multiple instances don't interfere with each other.
+TEST_F(OnceTest, MultipleInstances) {
+  static Once<int> once1(Function);
+  static Once<int> once2(SecondFunction);
+
+  EXPECT_EQ(&value_, once1.Get());
+  EXPECT_EQ(&second_result, once2.Get());
+  EXPECT_EQ(&value_, once1.Get());
+  EXPECT_EQ(&second_result, once2.Get());
+}
+
+// Tests calling Reset() to run the function a second time.
+TEST_F(OnceTest, Recalculate) {
+  Once<int> once(Function);
+  once.Reset();
+
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(1, times_run_);
+
+  value_ = 0;
+  once.Reset();
+  EXPECT_EQ(value_, *once.Get());
+  EXPECT_EQ(2, times_run_);
+}
+
+}  // namespace testing
+}  // namespace aos