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/*
* Copyright (C) 2017 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.
*/
#pragma once
#include <atomic>
#include <mutex>
#include <wtf/HashTraits.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/text/WTFString.h>
namespace WTF {
template<typename T> class ObjectIdentifier {
public:
ObjectIdentifier() = default;
ObjectIdentifier(HashTableDeletedValueType) : m_identifier(hashTableDeletedValue()) { }
bool isHashTableDeletedValue() const { return m_identifier == hashTableDeletedValue(); }
template<typename Encoder> void encode(Encoder& encoder) const
{
ASSERT(isValidIdentifier(m_identifier));
encoder << m_identifier;
}
template<typename Decoder> static std::optional<ObjectIdentifier> decode(Decoder& decoder)
{
std::optional<uint64_t> identifier;
decoder >> identifier;
if (!identifier)
return std::nullopt;
ASSERT(isValidIdentifier(*identifier));
return ObjectIdentifier { *identifier };
}
bool operator==(const ObjectIdentifier& other) const
{
return m_identifier == other.m_identifier;
}
bool operator!=(const ObjectIdentifier& other) const
{
return m_identifier != other.m_identifier;
}
uint64_t toUInt64() const { return m_identifier; }
explicit operator bool() const { return m_identifier; }
String loggingString() const
{
return String::number(m_identifier);
}
private:
template<typename U> friend ObjectIdentifier<U> generateObjectIdentifier();
template<typename U> friend ObjectIdentifier<U> generateThreadSafeObjectIdentifier();
template<typename U> friend ObjectIdentifier<U> makeObjectIdentifier(uint64_t);
friend struct HashTraits<ObjectIdentifier>;
template<typename U> friend struct ObjectIdentifierHash;
static uint64_t hashTableDeletedValue() { return std::numeric_limits<uint64_t>::max(); }
static bool isValidIdentifier(uint64_t identifier) { return identifier && identifier != hashTableDeletedValue(); }
explicit ObjectIdentifier(uint64_t identifier)
: m_identifier(identifier)
{
}
uint64_t m_identifier { 0 };
};
template<typename T> inline ObjectIdentifier<T> generateObjectIdentifier()
{
static uint64_t currentIdentifier;
return ObjectIdentifier<T> { ++currentIdentifier };
}
template<typename T> inline ObjectIdentifier<T> generateThreadSafeObjectIdentifier()
{
static LazyNeverDestroyed<std::atomic<uint64_t>> currentIdentifier;
static std::once_flag initializeCurrentIdentifier;
std::call_once(initializeCurrentIdentifier, [] {
currentIdentifier.construct(0);
});
return ObjectIdentifier<T> { ++currentIdentifier.get() };
}
template<typename T> inline ObjectIdentifier<T> makeObjectIdentifier(uint64_t identifier)
{
return ObjectIdentifier<T> { identifier };
}
template<typename T> struct ObjectIdentifierHash {
static unsigned hash(const ObjectIdentifier<T>& identifier) { return intHash(identifier.m_identifier); }
static bool equal(const ObjectIdentifier<T>& a, const ObjectIdentifier<T>& b) { return a == b; }
static const bool safeToCompareToEmptyOrDeleted = true;
};
template<typename T> struct HashTraits<ObjectIdentifier<T>> : SimpleClassHashTraits<ObjectIdentifier<T>> { };
template<typename T> struct DefaultHash<ObjectIdentifier<T>> {
typedef ObjectIdentifierHash<T> Hash;
};
} // namespace WTF
using WTF::ObjectIdentifier;
using WTF::generateObjectIdentifier;
using WTF::generateThreadSafeObjectIdentifier;
using WTF::makeObjectIdentifier;