include/ftl/flags.h - android_frameworks_native - Gitiles

 /*
  * Copyright 2020 The Android Open Source Project
  *
  * 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 <ftl/enum.h>
 #include <ftl/string.h>

 #include <bitset>
 #include <cstdint>
 #include <iterator>
 #include <string>
 #include <type_traits>

 // TODO(b/185536303): Align with FTL style.

 namespace android::ftl {

 /* A class for handling flags defined by an enum or enum class in a type-safe way. */
 template <typename F>
 class Flags {
     // F must be an enum or its underlying type is undefined. Theoretically we could specialize this
     // further to avoid this restriction but in general we want to encourage the use of enums
     // anyways.
     static_assert(std::is_enum_v<F>, "Flags type must be an enum");
     using U = std::underlying_type_t<F>;

 public:
     constexpr Flags(F f) : mFlags(static_cast<U>(f)) {}
     constexpr Flags() : mFlags(0) {}
     constexpr Flags(const Flags<F>& f) : mFlags(f.mFlags) {}

     // Provide a non-explicit construct for non-enum classes since they easily convert to their
     // underlying types (e.g. when used with bitwise operators). For enum classes, however, we
     // should force them to be explicitly constructed from their underlying types to make full use
     // of the type checker.
     template <typename T = U>
     constexpr Flags(T t, std::enable_if_t<!is_scoped_enum_v<F>, T>* = nullptr) : mFlags(t) {}

     template <typename T = U>
     explicit constexpr Flags(T t, std::enable_if_t<is_scoped_enum_v<F>, T>* = nullptr)
           : mFlags(t) {}

     class Iterator {
         using Bits = std::uint64_t;
         static_assert(sizeof(U) <= sizeof(Bits));

     public:
         constexpr Iterator() = default;
         Iterator(Flags<F> flags) : mRemainingFlags(flags.mFlags) { (*this)++; }

         // Pre-fix ++
         Iterator& operator++() {
             if (mRemainingFlags.none()) {
                 mCurrFlag = 0;
             } else {
                 // TODO: Replace with std::countr_zero in C++20.
                 const Bits bit = static_cast<Bits>(__builtin_ctzll(mRemainingFlags.to_ullong()));
                 mRemainingFlags.reset(static_cast<std::size_t>(bit));
                 mCurrFlag = static_cast<U>(static_cast<Bits>(1) << bit);
             }
             return *this;
         }

         // Post-fix ++
         Iterator operator++(int) {
             Iterator iter = *this;
             ++*this;
             return iter;
         }

         bool operator==(Iterator other) const {
             return mCurrFlag == other.mCurrFlag && mRemainingFlags == other.mRemainingFlags;
         }

         bool operator!=(Iterator other) const { return !(*this == other); }

         F operator*() const { return F{mCurrFlag}; }

         // iterator traits

         // In the future we could make this a bidirectional const iterator instead of a forward
         // iterator but it doesn't seem worth the added complexity at this point. This could not,
         // however, be made a non-const iterator as assigning one flag to another is a non-sensical
         // operation.
         using iterator_category = std::input_iterator_tag;
         using value_type = F;
         // Per the C++ spec, because input iterators are not assignable the iterator's reference
         // type does not actually need to be a reference. In fact, making it a reference would imply
         // that modifying it would change the underlying Flags object, which is obviously wrong for
         // the same reason this can't be a non-const iterator.
         using reference = F;
         using difference_type = void;
         using pointer = void;

     private:
         std::bitset<sizeof(Bits) * 8> mRemainingFlags;
         U mCurrFlag = 0;
     };

     /*
      * Tests whether the given flag is set.
      */
     bool test(F flag) const {
         U f = static_cast<U>(flag);
         return (f & mFlags) == f;
     }

     /* Tests whether any of the given flags are set */
     bool any(Flags<F> f) const { return (mFlags & f.mFlags) != 0; }

     /* Tests whether all of the given flags are set */
     bool all(Flags<F> f) const { return (mFlags & f.mFlags) == f.mFlags; }

     constexpr Flags<F> operator|(Flags<F> rhs) const { return static_cast<F>(mFlags | rhs.mFlags); }
     Flags<F>& operator|=(Flags<F> rhs) {
         mFlags = mFlags | rhs.mFlags;
         return *this;
     }

     Flags<F> operator&(Flags<F> rhs) const { return static_cast<F>(mFlags & rhs.mFlags); }
     Flags<F>& operator&=(Flags<F> rhs) {
         mFlags = mFlags & rhs.mFlags;
         return *this;
     }

     Flags<F> operator^(Flags<F> rhs) const { return static_cast<F>(mFlags ^ rhs.mFlags); }
     Flags<F>& operator^=(Flags<F> rhs) {
         mFlags = mFlags ^ rhs.mFlags;
         return *this;
     }

     Flags<F> operator~() { return static_cast<F>(~mFlags); }

     bool operator==(Flags<F> rhs) const { return mFlags == rhs.mFlags; }
     bool operator!=(Flags<F> rhs) const { return !operator==(rhs); }

     Flags<F>& operator=(const Flags<F>& rhs) {
         mFlags = rhs.mFlags;
         return *this;
     }

     inline Flags<F>& clear(Flags<F> f = static_cast<F>(~static_cast<U>(0))) {
         return *this &= ~f;
     }

     Iterator begin() const { return Iterator(*this); }

     Iterator end() const { return Iterator(); }

     /*
      * Returns the stored set of flags.
      *
      * Note that this returns the underlying type rather than the base enum class. This is because
      * the value is no longer necessarily a strict member of the enum since the returned value could
      * be multiple enum variants OR'd together.
      */
     U get() const { return mFlags; }

     std::string string() const {
         std::string result;
         bool first = true;
         U unstringified = 0;
         for (const F f : *this) {
             if (const auto flagName = flag_name(f)) {
                 appendFlag(result, flagName.value(), first);
             } else {
                 unstringified |= static_cast<U>(f);
             }
         }

         if (unstringified != 0) {
             constexpr auto radix = sizeof(U) == 1 ? Radix::kBin : Radix::kHex;
             appendFlag(result, to_string(unstringified, radix), first);
         }

         if (first) {
             result += "0x0";
         }

         return result;
     }

 private:
     U mFlags;

     static void appendFlag(std::string& str, const std::string_view& flag, bool& first) {
         if (first) {
             first = false;
         } else {
             str += " | ";
         }
         str += flag;
     }
 };

 // This namespace provides operator overloads for enum classes to make it easier to work with them
 // as flags. In order to use these, add them via a `using namespace` declaration.
 namespace flag_operators {

 template <typename F, typename = std::enable_if_t<is_scoped_enum_v<F>>>
 inline Flags<F> operator~(F f) {
     return static_cast<F>(~to_underlying(f));
 }

 template <typename F, typename = std::enable_if_t<is_scoped_enum_v<F>>>
 constexpr Flags<F> operator|(F lhs, F rhs) {
     return static_cast<F>(to_underlying(lhs) | to_underlying(rhs));
 }

 } // namespace flag_operators
 } // namespace android::ftl
	/*
	* Copyright 2020 The Android Open Source Project
	*
	* 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 <ftl/enum.h>
	#include <ftl/string.h>

	#include <bitset>
	#include <cstdint>
	#include <iterator>
	#include <string>
	#include <type_traits>

	// TODO(b/185536303): Align with FTL style.

	namespace android::ftl {

	/* A class for handling flags defined by an enum or enum class in a type-safe way. */
	template <typename F>
	class Flags {
	// F must be an enum or its underlying type is undefined. Theoretically we could specialize this
	// further to avoid this restriction but in general we want to encourage the use of enums
	// anyways.
	static_assert(std::is_enum_v<F>, "Flags type must be an enum");
	using U = std::underlying_type_t<F>;

	public:
	constexpr Flags(F f) : mFlags(static_cast<U>(f)) {}
	constexpr Flags() : mFlags(0) {}
	constexpr Flags(const Flags<F>& f) : mFlags(f.mFlags) {}

	// Provide a non-explicit construct for non-enum classes since they easily convert to their
	// underlying types (e.g. when used with bitwise operators). For enum classes, however, we
	// should force them to be explicitly constructed from their underlying types to make full use
	// of the type checker.
	template <typename T = U>
	constexpr Flags(T t, std::enable_if_t<!is_scoped_enum_v<F>, T>* = nullptr) : mFlags(t) {}

	template <typename T = U>
	explicit constexpr Flags(T t, std::enable_if_t<is_scoped_enum_v<F>, T>* = nullptr)
	: mFlags(t) {}

	class Iterator {
	using Bits = std::uint64_t;
	static_assert(sizeof(U) <= sizeof(Bits));

	public:
	constexpr Iterator() = default;
	Iterator(Flags<F> flags) : mRemainingFlags(flags.mFlags) { (*this)++; }

	// Pre-fix ++
	Iterator& operator++() {
	if (mRemainingFlags.none()) {
	mCurrFlag = 0;
	} else {
	// TODO: Replace with std::countr_zero in C++20.
	const Bits bit = static_cast<Bits>(__builtin_ctzll(mRemainingFlags.to_ullong()));
	mRemainingFlags.reset(static_cast<std::size_t>(bit));
	mCurrFlag = static_cast<U>(static_cast<Bits>(1) << bit);
	}
	return *this;
	}

	// Post-fix ++
	Iterator operator++(int) {
	Iterator iter = *this;
	++*this;
	return iter;
	}

	bool operator==(Iterator other) const {
	return mCurrFlag == other.mCurrFlag && mRemainingFlags == other.mRemainingFlags;
	}

	bool operator!=(Iterator other) const { return !(*this == other); }

	F operator*() const { return F{mCurrFlag}; }

	// iterator traits

	// In the future we could make this a bidirectional const iterator instead of a forward
	// iterator but it doesn't seem worth the added complexity at this point. This could not,
	// however, be made a non-const iterator as assigning one flag to another is a non-sensical
	// operation.
	using iterator_category = std::input_iterator_tag;
	using value_type = F;
	// Per the C++ spec, because input iterators are not assignable the iterator's reference
	// type does not actually need to be a reference. In fact, making it a reference would imply
	// that modifying it would change the underlying Flags object, which is obviously wrong for
	// the same reason this can't be a non-const iterator.
	using reference = F;
	using difference_type = void;
	using pointer = void;

	private:
	std::bitset<sizeof(Bits) * 8> mRemainingFlags;
	U mCurrFlag = 0;
	};

	/*
	* Tests whether the given flag is set.
	*/
	bool test(F flag) const {
	U f = static_cast<U>(flag);
	return (f & mFlags) == f;
	}

	/* Tests whether any of the given flags are set */
	bool any(Flags<F> f) const { return (mFlags & f.mFlags) != 0; }

	/* Tests whether all of the given flags are set */
	bool all(Flags<F> f) const { return (mFlags & f.mFlags) == f.mFlags; }

	constexpr Flags<F> operator\|(Flags<F> rhs) const { return static_cast<F>(mFlags \| rhs.mFlags); }
	Flags<F>& operator\|=(Flags<F> rhs) {
	mFlags = mFlags \| rhs.mFlags;
	return *this;
	}

	Flags<F> operator&(Flags<F> rhs) const { return static_cast<F>(mFlags & rhs.mFlags); }
	Flags<F>& operator&=(Flags<F> rhs) {
	mFlags = mFlags & rhs.mFlags;
	return *this;
	}

	Flags<F> operator^(Flags<F> rhs) const { return static_cast<F>(mFlags ^ rhs.mFlags); }
	Flags<F>& operator^=(Flags<F> rhs) {
	mFlags = mFlags ^ rhs.mFlags;
	return *this;
	}

	Flags<F> operator~() { return static_cast<F>(~mFlags); }

	bool operator==(Flags<F> rhs) const { return mFlags == rhs.mFlags; }
	bool operator!=(Flags<F> rhs) const { return !operator==(rhs); }

	Flags<F>& operator=(const Flags<F>& rhs) {
	mFlags = rhs.mFlags;
	return *this;
	}

	inline Flags<F>& clear(Flags<F> f = static_cast<F>(~static_cast<U>(0))) {
	return *this &= ~f;
	}

	Iterator begin() const { return Iterator(*this); }

	Iterator end() const { return Iterator(); }

	/*
	* Returns the stored set of flags.
	*
	* Note that this returns the underlying type rather than the base enum class. This is because
	* the value is no longer necessarily a strict member of the enum since the returned value could
	* be multiple enum variants OR'd together.
	*/
	U get() const { return mFlags; }

	std::string string() const {
	std::string result;
	bool first = true;
	U unstringified = 0;
	for (const F f : *this) {
	if (const auto flagName = flag_name(f)) {
	appendFlag(result, flagName.value(), first);
	} else {
	unstringified \|= static_cast<U>(f);
	}
	}

	if (unstringified != 0) {
	constexpr auto radix = sizeof(U) == 1 ? Radix::kBin : Radix::kHex;
	appendFlag(result, to_string(unstringified, radix), first);
	}

	if (first) {
	result += "0x0";
	}

	return result;
	}

	private:
	U mFlags;

	static void appendFlag(std::string& str, const std::string_view& flag, bool& first) {
	if (first) {
	first = false;
	} else {
	str += " \| ";
	}
	str += flag;
	}
	};

	// This namespace provides operator overloads for enum classes to make it easier to work with them
	// as flags. In order to use these, add them via a `using namespace` declaration.
	namespace flag_operators {

	template <typename F, typename = std::enable_if_t<is_scoped_enum_v<F>>>
	inline Flags<F> operator~(F f) {
	return static_cast<F>(~to_underlying(f));
	}

	template <typename F, typename = std::enable_if_t<is_scoped_enum_v<F>>>
	constexpr Flags<F> operator\|(F lhs, F rhs) {
	return static_cast<F>(to_underlying(lhs) \| to_underlying(rhs));
	}

	} // namespace flag_operators
	} // namespace android::ftl