Turn FeatureSet into a generic EnumBitset

oi/EnumBitset.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <bitset>
+
+template <typename T, size_t N>
+class EnumBitset {
+ private:
+  using BitsetType = std::bitset<N>;
+
+ public:
+  EnumBitset() = default;
+  EnumBitset(std::initializer_list<T> values) {
+    for (auto v : values) {
+      (*this)[v] = true;
+    }
+  }
+
+  constexpr bool operator[](T v) const {
+    return bitset[static_cast<size_t>(v)];
+  }
+  typename BitsetType::reference operator[](T v) {
+    return bitset[static_cast<size_t>(v)];
+  }
+
+ private:
+  BitsetType bitset;
+};

oi/Features.cpp

@@ -45,10 +45,4 @@ const char* featureToStr(Feature f) {
   }
 }
 
-FeatureSet::FeatureSet(std::initializer_list<Feature> features) {
-  for (auto f : features) {
-    (*this)[f] = true;
-  }
-}
-
 }  // namespace ObjectIntrospection

oi/Features.h

@@ -16,9 +16,10 @@
 #pragma once
 
 #include <array>
-#include <bitset>
 #include <string_view>
 
+#include "oi/EnumBitset.h"
+
 #define OI_FEATURE_LIST                         \
   X(ChaseRawPointers, "chase-raw-pointers")     \
   X(PackStructs, "pack-structs")                \
@@ -45,23 +46,7 @@ constexpr std::array allFeatures = {
 #undef X
 };
 
-class FeatureSet {
- private:
-  using BitsetType = std::bitset<allFeatures.size() + 1>;
-
- public:
-  FeatureSet() = default;
-  FeatureSet(std::initializer_list<Feature>);
-
-  constexpr bool operator[](Feature f) const {
-    return bitset[(size_t)f];
-  }
-  BitsetType::reference operator[](Feature f) {
-    return bitset[(size_t)f];
-  }
-
- private:
-  BitsetType bitset;
-};
+// Use "size+1" to account for UnknownFeature"
+using FeatureSet = EnumBitset<Feature, allFeatures.size() + 1>;
 
 }  // namespace ObjectIntrospection