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/*
* Copyright (C) 2010, Google 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 <compare>
#include <wtf/HashFunctions.h>
#include <wtf/HashTraits.h>
namespace WTF {
// An abstract number of element in a sequence. The sequence has a first element.
// This type should be used instead of integer because 2 contradicting traditions can
// call a first element '0' or '1' which makes integer type ambiguous.
class OrdinalNumber {
WTF_MAKE_FAST_ALLOCATED;
public:
static OrdinalNumber beforeFirst() { return OrdinalNumber(-1); }
static OrdinalNumber fromZeroBasedInt(int zeroBasedInt) { return OrdinalNumber(zeroBasedInt); }
static OrdinalNumber fromOneBasedInt(int oneBasedInt) { return OrdinalNumber(oneBasedInt - 1); }
OrdinalNumber() : m_zeroBasedValue(0) { }
int zeroBasedInt() const { return m_zeroBasedValue; }
int oneBasedInt() const { return m_zeroBasedValue + 1; }
friend bool operator==(OrdinalNumber, OrdinalNumber) = default;
friend std::strong_ordering operator<=>(OrdinalNumber, OrdinalNumber) = default;
private:
OrdinalNumber(int zeroBasedInt) : m_zeroBasedValue(zeroBasedInt) { }
int m_zeroBasedValue;
};
template<typename T> struct DefaultHash;
template<> struct DefaultHash<OrdinalNumber> {
static unsigned hash(OrdinalNumber key) { return intHash(static_cast<unsigned>(key.zeroBasedInt())); }
static bool equal(OrdinalNumber a, OrdinalNumber b) { return a == b; }
static constexpr bool safeToCompareToEmptyOrDeleted = true;
};
template<typename T> struct HashTraits;
template<> struct HashTraits<OrdinalNumber> : GenericHashTraits<OrdinalNumber> {
static void constructDeletedValue(OrdinalNumber& slot)
{
slot = OrdinalNumber::beforeFirst();
}
static bool isDeletedValue(OrdinalNumber value)
{
return value == OrdinalNumber::beforeFirst();
}
};
}
using WTF::OrdinalNumber;
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