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/*
* Copyright (C) 2017-2021 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 <wtf/HashFunctions.h>
#include <wtf/HashTraits.h>
#include <wtf/text/TextStream.h>
#include <wtf/text/WTFString.h>
namespace WebKit {
// MonotonicObjectIdentifier is similar to ObjectIdentifier but it can be monotonically
// increased in place.
// FIXME: merge ObjectIdentifier and MonotonicObjectIdentifier in one class.
template<typename T> class MonotonicObjectIdentifier {
public:
MonotonicObjectIdentifier() = default;
MonotonicObjectIdentifier(WTF::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<MonotonicObjectIdentifier> decode(Decoder& decoder)
{
std::optional<uint64_t> identifier;
decoder >> identifier;
if (!identifier)
return std::nullopt;
ASSERT(isValidIdentifier(*identifier));
return MonotonicObjectIdentifier { *identifier };
}
bool operator==(const MonotonicObjectIdentifier& other) const
{
return m_identifier == other.m_identifier;
}
bool operator>(const MonotonicObjectIdentifier& other) const
{
return m_identifier > other.m_identifier;
}
bool operator>=(const MonotonicObjectIdentifier& other) const
{
return m_identifier >= other.m_identifier;
}
bool operator<(const MonotonicObjectIdentifier& other) const
{
return m_identifier < other.m_identifier;
}
bool operator<=(const MonotonicObjectIdentifier& other) const
{
return m_identifier <= other.m_identifier;
}
MonotonicObjectIdentifier& increment()
{
++m_identifier;
return *this;
}
MonotonicObjectIdentifier next() const
{
return MonotonicObjectIdentifier(m_identifier + 1);
}
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 MonotonicObjectIdentifier<U> makeMonotonicObjectIdentifier(uint64_t);
friend struct HashTraits<MonotonicObjectIdentifier>;
template<typename U> friend struct MonotonicObjectIdentifierHash;
static uint64_t hashTableDeletedValue() { return std::numeric_limits<uint64_t>::max(); }
static bool isValidIdentifier(uint64_t identifier) { return identifier != hashTableDeletedValue(); }
explicit MonotonicObjectIdentifier(uint64_t identifier)
: m_identifier(identifier)
{
}
uint64_t m_identifier { 0 };
};
template<typename T>
inline int64_t operator-(const MonotonicObjectIdentifier<T>& a, const MonotonicObjectIdentifier<T>& b)
{
CheckedInt64 result = CheckedInt64(a.toUInt64() - b.toUInt64());
return result.hasOverflowed() ? 0 : result.value();
}
template<typename T>
TextStream& operator<<(TextStream& ts, const MonotonicObjectIdentifier<T>& identifier)
{
ts << identifier.toUInt64();
return ts;
}
} // namespace WebKit
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