Merging upstream version 125.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 59 insertions, 23 deletions

diff --git a/mfbt/EnumTypeTraits.h b/mfbt/EnumTypeTraits.h
index 528e1db8a7..09ead3d0e9 100644
--- a/mfbt/EnumTypeTraits.h
+++ b/mfbt/EnumTypeTraits.h
@@ -61,29 +61,6 @@ struct EnumTypeFitsWithin
                 "must provide an integral type");
 };
 
-/*
- * Provides information about highest enum member value.
- * Each specialization of struct MaxEnumValue should define
- * "static constexpr unsigned int value".
- *
- * example:
- *
- *   enum ExampleEnum
- *   {
- *     CAT = 0,
- *     DOG,
- *     HAMSTER
- *   };
- *
- *   template <>
- *   struct MaxEnumValue<ExampleEnum>
- *   {
- *     static constexpr unsigned int value = static_cast<unsigned int>(HAMSTER);
- *   };
- */
-template <typename T>
-struct MaxEnumValue;  // no need to define the primary template
-
 /**
  * Get the underlying value of an enum, but typesafe.
  *
@@ -108,6 +85,65 @@ inline constexpr auto UnderlyingValue(const T v) {
   return static_cast<typename std::underlying_type<T>::type>(v);
 }
 
+/*
+ * Specialize either MaxContiguousEnumValue or MaxEnumValue to provide the
+ * highest enum member value for an enum class. Note that specializing
+ * MaxContiguousEnumValue will make MaxEnumValue just take its value from the
+ * MaxContiguousEnumValue specialization.
+ *
+ * Specialize MinContiguousEnumValue and MaxContiguousEnumValue to provide both
+ * lowest and highest enum member values for an enum class with contiguous
+ * values.
+ *
+ * Each specialization of these structs should define "static constexpr" member
+ * variable named "value".
+ *
+ * example:
+ *
+ *   enum ExampleEnum
+ *   {
+ *     CAT = 0,
+ *     DOG,
+ *     HAMSTER
+ *   };
+ *
+ *   template <>
+ *   struct MaxEnumValue<ExampleEnum>
+ *   {
+ *     static constexpr ExampleEnumvalue = HAMSTER;
+ *   };
+ */
+
+template <typename T>
+struct MinContiguousEnumValue {
+  static constexpr T value = static_cast<T>(0);
+};
+
+template <typename T>
+struct MaxContiguousEnumValue;
+
+template <typename T>
+struct MaxEnumValue {
+  static constexpr auto value = MaxContiguousEnumValue<T>::value;
+};
+
+// Provides the min and max values for a contiguous enum (requires at least
+// MaxContiguousEnumValue to be defined).
+template <typename T>
+struct ContiguousEnumValues {
+  static constexpr auto min = MinContiguousEnumValue<T>::value;
+  static constexpr auto max = MaxContiguousEnumValue<T>::value;
+};
+
+// Provides the total number of values for a contiguous enum (requires at least
+// MaxContiguousEnumValue to be defined).
+template <typename T>
+struct ContiguousEnumSize {
+  static constexpr size_t value =
+      UnderlyingValue(ContiguousEnumValues<T>::max) + 1 -
+      UnderlyingValue(ContiguousEnumValues<T>::min);
+};
+
 }  // namespace mozilla
 
 #endif /* mozilla_EnumTypeTraits_h */