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/*
* Copyright (C) 2016 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef OptionSet_h
#define OptionSet_h
#include <initializer_list>
#include <iterator>
#include <type_traits>
#include <wtf/Assertions.h>
#include <wtf/MathExtras.h>
namespace WTF {
// OptionSet is a class that represents a set of enumerators in a space-efficient manner. The enumerators
// must be powers of two greater than 0. This class is useful as a replacement for passing a bitmask of
// enumerators around.
template<typename T> class OptionSet {
static_assert(std::is_enum<T>::value, "T is not an enum type");
typedef typename std::make_unsigned<typename std::underlying_type<T>::type>::type StorageType;
public:
template<typename StorageType> class Iterator {
public:
// Isolate the rightmost set bit.
T operator*() const { return static_cast<T>(m_value & -m_value); }
// Iterates from smallest to largest enum value by turning off the rightmost set bit.
Iterator& operator++()
{
m_value &= m_value - 1;
return *this;
}
Iterator& operator++(int) = delete;
bool operator==(const Iterator& other) const { return m_value == other.m_value; }
bool operator!=(const Iterator& other) const { return m_value != other.m_value; }
private:
Iterator(StorageType value) : m_value(value) { }
friend OptionSet;
StorageType m_value;
};
using iterator = Iterator<StorageType>;
static OptionSet fromRaw(StorageType storageType)
{
return OptionSet(static_cast<T>(storageType), FromRawValue);
}
constexpr OptionSet() = default;
#if ASSERT_DISABLED
constexpr OptionSet(T t)
: m_storage(static_cast<StorageType>(t))
{
}
#else
OptionSet(T t)
: m_storage(static_cast<StorageType>(t))
{
ASSERT_WITH_MESSAGE(hasOneBitSet(static_cast<StorageType>(t)), "Enumerator is not a positive power of two.");
}
#endif
// FIXME: Make this constexpr once we adopt C++14 as C++11 does not support for-loops
// in a constexpr function.
OptionSet(std::initializer_list<T> initializerList)
{
for (auto& option : initializerList) {
ASSERT_WITH_MESSAGE(hasOneBitSet(static_cast<StorageType>(option)), "Enumerator is not a positive power of two.");
m_storage |= static_cast<StorageType>(option);
}
}
constexpr StorageType toRaw() const { return m_storage; }
constexpr bool isEmpty() const { return !m_storage; }
constexpr iterator begin() const { return m_storage; }
constexpr iterator end() const { return 0; }
constexpr bool contains(OptionSet optionSet) const
{
return m_storage & optionSet.m_storage;
}
friend OptionSet& operator|=(OptionSet& lhs, OptionSet rhs)
{
lhs.m_storage |= rhs.m_storage;
return lhs;
}
private:
enum InitializationTag { FromRawValue };
constexpr OptionSet(T t, InitializationTag)
: m_storage(static_cast<StorageType>(t))
{
}
StorageType m_storage { 0 };
};
}
using WTF::OptionSet;
#endif // OptionSet_h
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