1 files changed, 181 insertions, 0 deletions
diff --git a/mfbt/tests/TestSaturate.cpp b/mfbt/tests/TestSaturate.cpp
new file mode 100644
index 0000000000..500c9eed7f
--- /dev/null
+++ b/mfbt/tests/TestSaturate.cpp
@@ -0,0 +1,181 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <mozilla/Saturate.h>
+
+#include <mozilla/Assertions.h>
+
+#include <limits>
+
+using mozilla::detail::Saturate;
+
+#define A(a) MOZ_RELEASE_ASSERT(a, "Test \'" #a "\'  failed.")
+
+static const unsigned long sNumOps = 32;
+
+template <typename T>
+static T StartValue() {
+  // Specialize |StartValue| for the given type.
+  A(false);
+}
+
+template <>
+int8_t StartValue<int8_t>() {
+  return 0;
+}
+
+template <>
+int16_t StartValue<int16_t>() {
+  return 0;
+}
+
+template <>
+int32_t StartValue<int32_t>() {
+  return 0;
+}
+
+template <>
+uint8_t StartValue<uint8_t>() {
+  // Picking a value near middle of uint8_t's range.
+  return static_cast<uint8_t>(std::numeric_limits<int8_t>::max());
+}
+
+template <>
+uint16_t StartValue<uint16_t>() {
+  // Picking a value near middle of uint16_t's range.
+  return static_cast<uint8_t>(std::numeric_limits<int16_t>::max());
+}
+
+template <>
+uint32_t StartValue<uint32_t>() {
+  // Picking a value near middle of uint32_t's range.
+  return static_cast<uint8_t>(std::numeric_limits<int32_t>::max());
+}
+
+// Add
+//
+
+template <typename T>
+static void TestPrefixIncr() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A(++value == ++satValue);
+  }
+}
+
+template <typename T>
+static void TestPostfixIncr() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A(value++ == satValue++);
+  }
+}
+
+template <typename T>
+static void TestAdd() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A((value + i) == (satValue + i));
+  }
+}
+
+// Subtract
+//
+
+template <typename T>
+static void TestPrefixDecr() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A(--value == --satValue);
+  }
+}
+
+template <typename T>
+static void TestPostfixDecr() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A(value-- == satValue--);
+  }
+}
+
+template <typename T>
+static void TestSub() {
+  T value = StartValue<T>();
+  Saturate<T> satValue(value);
+
+  for (T i = 0; i < static_cast<T>(sNumOps); ++i) {
+    A((value - i) == (satValue - i));
+  }
+}
+
+// Corner cases near bounds
+//
+
+template <typename T>
+static void TestUpperBound() {
+  Saturate<T> satValue(std::numeric_limits<T>::max());
+
+  A(--satValue == (std::numeric_limits<T>::max() - 1));
+  A(++satValue == (std::numeric_limits<T>::max()));
+  A(++satValue == (std::numeric_limits<T>::max()));      // don't overflow here
+  A(++satValue == (std::numeric_limits<T>::max()));      // don't overflow here
+  A(--satValue == (std::numeric_limits<T>::max() - 1));  // back at (max - 1)
+  A(--satValue == (std::numeric_limits<T>::max() - 2));
+}
+
+template <typename T>
+static void TestLowerBound() {
+  Saturate<T> satValue(std::numeric_limits<T>::min());
+
+  A(++satValue == (std::numeric_limits<T>::min() + 1));
+  A(--satValue == (std::numeric_limits<T>::min()));
+  A(--satValue == (std::numeric_limits<T>::min()));      // don't overflow here
+  A(--satValue == (std::numeric_limits<T>::min()));      // don't overflow here
+  A(++satValue == (std::numeric_limits<T>::min() + 1));  // back at (max + 1)
+  A(++satValue == (std::numeric_limits<T>::min() + 2));
+}
+
+// Framework
+//
+
+template <typename T>
+static void TestAll() {
+  // Assert that we don't accidently hit type's range limits in tests.
+  const T value = StartValue<T>();
+  A(std::numeric_limits<T>::min() + static_cast<T>(sNumOps) <= value);
+  A(std::numeric_limits<T>::max() - static_cast<T>(sNumOps) >= value);
+
+  TestPrefixIncr<T>();
+  TestPostfixIncr<T>();
+  TestAdd<T>();
+
+  TestPrefixDecr<T>();
+  TestPostfixDecr<T>();
+  TestSub<T>();
+
+  TestUpperBound<T>();
+  TestLowerBound<T>();
+}
+
+int main() {
+  TestAll<int8_t>();
+  TestAll<int16_t>();
+  TestAll<int32_t>();
+  TestAll<uint8_t>();
+  TestAll<uint16_t>();
+  TestAll<uint32_t>();
+  return 0;
+}