Bug 1297306 - part4:rename IsEnumFittingWithin with EnumTypeFitsWithi…

…n and move it to mfbt/EnumTypeTraits.h. r=froydnj

With this change, we could share this EnumTypeTraits between files easily.

MozReview-Commit-ID: 9Q2augati7l

layout/style/StyleAnimationValue.h

@@ -449,7 +449,7 @@ class StyleAnimationValue {
            typename = typename std::enable_if<std::is_enum<T>::value>::type>
   void SetIntValue(T aInt, Unit aUnit)
   {
-    static_assert(mozilla::IsEnumFittingWithin<T, int32_t>::value,
+    static_assert(mozilla::EnumTypeFitsWithin<T, int32_t>::value,
                   "aValue must be an enum that fits within mValue.mInt");
     SetIntValue(static_cast<int32_t>(aInt), aUnit);
   }

layout/style/nsCSSProps.h

@@ -19,6 +19,7 @@
 #include "nsCSSKeywords.h"
 #include "mozilla/CSSEnabledState.h"
 #include "mozilla/UseCounter.h"
+#include "mozilla/EnumTypeTraits.h"
 
 // Length of the "--" prefix on custom names (such as custom property names,
 // and, in the future, custom media query names).
@@ -327,24 +328,6 @@ enum nsStyleAnimType {
   eStyleAnimType_None
 };
 
-namespace mozilla {
-
-// Type trait that determines whether the integral or enum type Type can fit
-// within the integral type Storage without loss.
-template<typename T, typename Storage>
-struct IsEnumFittingWithin
-  : IntegralConstant<
-      bool,
-      std::is_integral<Storage>::value &&
-      std::numeric_limits<typename std::underlying_type<T>::type>::min() >=
-        std::numeric_limits<Storage>::min() &&
-      std::numeric_limits<typename std::underlying_type<T>::type>::max() <=
-        std::numeric_limits<Storage>::max()
-    >
-{};
-
-} // namespace mozilla
-
 class nsCSSProps {
 public:
   typedef mozilla::CSSEnabledState EnabledState;
@@ -366,7 +349,7 @@ class nsCSSProps {
       : mKeyword(aKeyword)
       , mValue(static_cast<int16_t>(aValue))
     {
-      static_assert(mozilla::IsEnumFittingWithin<T, int16_t>::value,
+      static_assert(mozilla::EnumTypeFitsWithin<T, int16_t>::value,
                     "aValue must be an enum that fits within mValue");
     }
 
@@ -452,7 +435,7 @@ class nsCSSProps {
   static nsCSSKeyword ValueToKeywordEnum(T aValue,
                                          const KTableEntry aTable[])
   {
-    static_assert(mozilla::IsEnumFittingWithin<T, int16_t>::value,
+    static_assert(mozilla::EnumTypeFitsWithin<T, int16_t>::value,
                   "aValue must be an enum that fits within KTableEntry::mValue");
     return ValueToKeywordEnum(static_cast<int16_t>(aValue), aTable);
   }
@@ -464,7 +447,7 @@ class nsCSSProps {
   static const nsAFlatCString& ValueToKeyword(T aValue,
                                               const KTableEntry aTable[])
   {
-    static_assert(mozilla::IsEnumFittingWithin<T, int16_t>::value,
+    static_assert(mozilla::EnumTypeFitsWithin<T, int16_t>::value,
                   "aValue must be an enum that fits within KTableEntry::mValue");
     return ValueToKeyword(static_cast<int16_t>(aValue), aTable);
   }

layout/style/nsCSSValue.h

@@ -758,7 +758,7 @@ class nsCSSValue {
            typename = typename std::enable_if<std::is_enum<T>::value>::type>
   void SetIntValue(T aValue, nsCSSUnit aUnit)
   {
-    static_assert(mozilla::IsEnumFittingWithin<T, int32_t>::value,
+    static_assert(mozilla::EnumTypeFitsWithin<T, int32_t>::value,
                   "aValue must be an enum that fits within mValue.mInt");
     SetIntValue(static_cast<int32_t>(aValue), aUnit);
   }

mfbt/EnumTypeTraits.h

@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/* Type traits for enums. */
+
+#ifndef mozilla_EnumTypeTraits_h
+#define mozilla_EnumTypeTraits_h
+
+#include <type_traits>
+
+namespace mozilla {
+
+namespace detail {
+
+template<size_t EnumSize, bool EnumSigned, size_t StorageSize, bool StorageSigned>
+struct EnumFitsWithinHelper;
+
+// Signed enum, signed storage.
+template<size_t EnumSize, size_t StorageSize>
+struct EnumFitsWithinHelper<EnumSize, true, StorageSize, true>
+  : public std::integral_constant<bool, (EnumSize <= StorageSize)>
+{};
+
+// Signed enum, unsigned storage.
+template<size_t EnumSize, size_t StorageSize>
+struct EnumFitsWithinHelper<EnumSize, true, StorageSize, false>
+  : public std::integral_constant<bool, false>
+{};
+
+// Unsigned enum, signed storage.
+template<size_t EnumSize, size_t StorageSize>
+struct EnumFitsWithinHelper<EnumSize, false, StorageSize, true>
+  : public std::integral_constant<bool, (EnumSize * 2 <= StorageSize)>
+{};
+
+// Unsigned enum, unsigned storage.
+template<size_t EnumSize, size_t StorageSize>
+struct EnumFitsWithinHelper<EnumSize, false, StorageSize, false>
+  : public std::integral_constant<bool, (EnumSize <= StorageSize)>
+{};
+
+} // namespace detail
+
+/*
+ * Type trait that determines whether the enum type T can fit within the
+ * integral type Storage without data loss. This trait should be used with
+ * caution with an enum type whose underlying type has not been explicitly
+ * specified: for such enums, the C++ implementation is free to choose a type
+ * no smaller than int whose range encompasses all possible values of the enum.
+ * So for an enum with only small non-negative values, the underlying type may
+ * be either int or unsigned int, depending on the whims of the implementation.
+ */
+template<typename T, typename Storage>
+struct EnumTypeFitsWithin
+  : public detail::EnumFitsWithinHelper<
+      sizeof(T),
+      std::is_signed<typename std::underlying_type<T>::type>::value,
+      sizeof(Storage),
+      std::is_signed<Storage>::value
+    >
+{
+  static_assert(std::is_enum<T>::value, "must provide an enum type");
+  static_assert(std::is_integral<Storage>::value, "must provide an integral type");
+};
+
+} // namespace mozilla
+
+#endif /* mozilla_EnumTypeTraits_h */

mfbt/moz.build

@@ -39,6 +39,7 @@ EXPORTS.mozilla = [
     'EnumeratedArray.h',
     'EnumeratedRange.h',
     'EnumSet.h',
+    'EnumTypeTraits.h',
     'FastBernoulliTrial.h',
     'FloatingPoint.h',
     'Function.h',

mfbt/tests/TestEnumTypeTraits.cpp

@@ -0,0 +1,136 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/IntegerTypeTraits.h"
+#include "mozilla/EnumTypeTraits.h"
+
+using namespace mozilla;
+
+/* Feature check for EnumTypeFitsWithin. */
+
+#define MAKE_FIXED_EMUM_FOR_TYPE(IntType)                               \
+  enum FixedEnumFor_##IntType : IntType {                               \
+    A_##IntType,                                                        \
+    B_##IntType,                                                        \
+    C_##IntType,                                                        \
+  };
+
+template<typename EnumType, typename IntType>
+static void
+TestShouldFit()
+{
+  static_assert(EnumTypeFitsWithin<EnumType, IntType>::value,
+                "Should fit within exact/promoted integral type");
+}
+
+template<typename EnumType, typename IntType>
+static void
+TestShouldNotFit()
+{
+  static_assert(!EnumTypeFitsWithin<EnumType, IntType>::value,
+                "Should not fit within");
+}
+
+int
+main()
+{
+  // check for int8_t
+  MAKE_FIXED_EMUM_FOR_TYPE(int8_t);
+  TestShouldFit<FixedEnumFor_int8_t, int8_t>();
+  TestShouldFit<FixedEnumFor_int8_t, int16_t>();
+  TestShouldFit<FixedEnumFor_int8_t, int32_t>();
+  TestShouldFit<FixedEnumFor_int8_t, int64_t>();
+
+  TestShouldNotFit<FixedEnumFor_int8_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_int8_t, uint16_t>();
+  TestShouldNotFit<FixedEnumFor_int8_t, uint32_t>();
+  TestShouldNotFit<FixedEnumFor_int8_t, uint64_t>();
+
+  // check for uint8_t
+  MAKE_FIXED_EMUM_FOR_TYPE(uint8_t);
+  TestShouldFit<FixedEnumFor_uint8_t, uint8_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, uint16_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, uint32_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, uint64_t>();
+
+  TestShouldNotFit<FixedEnumFor_uint8_t, int8_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, int16_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, int32_t>();
+  TestShouldFit<FixedEnumFor_uint8_t, int64_t>();
+
+  // check for int16_t
+  MAKE_FIXED_EMUM_FOR_TYPE(int16_t);
+  TestShouldNotFit<FixedEnumFor_int16_t, int8_t>();
+  TestShouldFit<FixedEnumFor_int16_t, int16_t>();
+  TestShouldFit<FixedEnumFor_int16_t, int32_t>();
+  TestShouldFit<FixedEnumFor_int16_t, int64_t>();
+
+  TestShouldNotFit<FixedEnumFor_int16_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_int16_t, uint16_t>();
+  TestShouldNotFit<FixedEnumFor_int16_t, uint32_t>();
+  TestShouldNotFit<FixedEnumFor_int16_t, uint64_t>();
+
+  // check for uint16_t
+  MAKE_FIXED_EMUM_FOR_TYPE(uint16_t);
+  TestShouldNotFit<FixedEnumFor_uint16_t, uint8_t>();
+  TestShouldFit<FixedEnumFor_uint16_t, uint16_t>();
+  TestShouldFit<FixedEnumFor_uint16_t, uint32_t>();
+  TestShouldFit<FixedEnumFor_uint16_t, uint64_t>();
+
+  TestShouldNotFit<FixedEnumFor_uint16_t, int8_t>();
+  TestShouldNotFit<FixedEnumFor_uint16_t, int16_t>();
+  TestShouldFit<FixedEnumFor_uint16_t, int32_t>();
+  TestShouldFit<FixedEnumFor_uint16_t, int64_t>();
+
+  // check for int32_t
+  MAKE_FIXED_EMUM_FOR_TYPE(int32_t);
+  TestShouldNotFit<FixedEnumFor_int32_t, int8_t>();
+  TestShouldNotFit<FixedEnumFor_int32_t, int16_t>();
+  TestShouldFit<FixedEnumFor_int32_t, int32_t>();
+  TestShouldFit<FixedEnumFor_int32_t, int64_t>();
+
+  TestShouldNotFit<FixedEnumFor_int32_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_int32_t, uint16_t>();
+  TestShouldNotFit<FixedEnumFor_int32_t, uint32_t>();
+  TestShouldNotFit<FixedEnumFor_int32_t, uint64_t>();
+
+  // check for uint32_t
+  MAKE_FIXED_EMUM_FOR_TYPE(uint32_t);
+  TestShouldNotFit<FixedEnumFor_uint32_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_uint32_t, uint16_t>();
+  TestShouldFit<FixedEnumFor_uint32_t, uint32_t>();
+  TestShouldFit<FixedEnumFor_uint32_t, uint64_t>();
+
+  TestShouldNotFit<FixedEnumFor_uint32_t, int8_t>();
+  TestShouldNotFit<FixedEnumFor_uint32_t, int16_t>();
+  TestShouldNotFit<FixedEnumFor_uint32_t, int32_t>();
+  TestShouldFit<FixedEnumFor_uint32_t, int64_t>();
+
+  // check for int64_t
+  MAKE_FIXED_EMUM_FOR_TYPE(int64_t);
+  TestShouldNotFit<FixedEnumFor_int64_t, int8_t>();
+  TestShouldNotFit<FixedEnumFor_int64_t, int16_t>();
+  TestShouldNotFit<FixedEnumFor_int64_t, int32_t>();
+  TestShouldFit<FixedEnumFor_int64_t, int64_t>();
+
+  TestShouldNotFit<FixedEnumFor_int64_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_int64_t, uint16_t>();
+  TestShouldNotFit<FixedEnumFor_int64_t, uint32_t>();
+  TestShouldNotFit<FixedEnumFor_int64_t, uint64_t>();
+
+  // check for uint64_t
+  MAKE_FIXED_EMUM_FOR_TYPE(uint64_t);
+  TestShouldNotFit<FixedEnumFor_uint64_t, uint8_t>();
+  TestShouldNotFit<FixedEnumFor_uint64_t, uint16_t>();
+  TestShouldNotFit<FixedEnumFor_uint64_t, uint32_t>();
+  TestShouldFit<FixedEnumFor_uint64_t, uint64_t>();
+
+  TestShouldNotFit<FixedEnumFor_uint64_t, int8_t>();
+  TestShouldNotFit<FixedEnumFor_uint64_t, int16_t>();
+  TestShouldNotFit<FixedEnumFor_uint64_t, int32_t>();
+  TestShouldNotFit<FixedEnumFor_uint64_t, int64_t>();
+
+  return 0;
+}

mfbt/tests/moz.build

@@ -17,6 +17,7 @@ CppUnitTests([
     'TestCountZeroes',
     'TestEndian',
     'TestEnumSet',
+    'TestEnumTypeTraits',
     'TestFastBernoulliTrial',
     'TestFloatingPoint',
     'TestFunction',

testing/cppunittest.ini

@@ -33,6 +33,7 @@ skip-if = os == 'b2g' || (os == 'android' && debug) # Bug 1054249
 skip-if = os != 'win'
 [TestEndian]
 [TestEnumSet]
+[TestEnumTypeTraits]
 [TestFastBernoulliTrial]
 [TestFile]
 [TestFloatingPoint]