/****************************************************************************
**
** Copyright (C) 2021 The Qt Company Ltd.
** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
** Contact: https://www.qt.io/licensing/
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** information use the contact form at https://www.qt.io/contact-us.
**
** $QT_END_LICENSE$
**
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****************************************************************************/

#ifndef QHASHFUNCTIONS_H
#define QHASHFUNCTIONS_H

#include <QtCore/qstring.h>
#include <QtCore/qpair.h>

#include <numeric> // for std::accumulate
#include <functional> // for std::hash

#if 0
#pragma qt_class(QHashFunctions)
#endif

#if defined(Q_CC_MSVC)
#pragma warning( push )
#pragma warning( disable : 4311 ) // disable pointer truncation warning
#pragma warning( disable : 4127 ) // conditional expression is constant
#endif

QT_BEGIN_NAMESPACE

class QBitArray;
class QByteArray;
class QString;
class QStringRef;
class QLatin1String;

Q_CORE_EXPORT int qGlobalQHashSeed();
Q_CORE_EXPORT void qSetGlobalQHashSeed(int newSeed);

Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHashBits(const void *p, size_t size, uint seed = 0) noexcept;

Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(char key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uchar key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(signed char key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ushort key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(short key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uint key, uint seed = 0) noexcept { return key ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(int key, uint seed = 0) noexcept { return uint(key) ^ seed; }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ulong key, uint seed = 0) noexcept
{
    return (sizeof(ulong) > sizeof(uint))
        ? (uint(((key >> (8 * sizeof(uint) - 1)) ^ key) & (~0U)) ^ seed)
        : (uint(key & (~0U)) ^ seed);
}
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(long key, uint seed = 0) noexcept { return qHash(ulong(key), seed); }
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(quint64 key, uint seed = 0) noexcept
{
    return uint(((key >> (8 * sizeof(uint) - 1)) ^ key) & (~0U)) ^ seed;
}
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(qint64 key, uint seed = 0) noexcept { return qHash(quint64(key), seed); }
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(float key, uint seed = 0) noexcept;
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(double key, uint seed = 0) noexcept;
#if !defined(Q_OS_DARWIN) || defined(Q_CLANG_QDOC)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(long double key, uint seed = 0) noexcept;
#endif
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(const QChar key, uint seed = 0) noexcept { return qHash(key.unicode(), seed); }
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QByteArray &key, uint seed = 0) noexcept;
#if QT_STRINGVIEW_LEVEL < 2
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QString &key, uint seed = 0) noexcept;
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QStringRef &key, uint seed = 0) noexcept;
#endif
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(QStringView key, uint seed = 0) noexcept;
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QBitArray &key, uint seed = 0) noexcept;
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(QLatin1String key, uint seed = 0) noexcept;
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qt_hash(QStringView key, uint chained = 0) noexcept;

Q_DECL_CONST_FUNCTION inline uint qHash(std::nullptr_t, uint seed = 0) noexcept
{
    return qHash(reinterpret_cast<quintptr>(nullptr), seed);
}

template <class T> inline uint qHash(const T *key, uint seed = 0) noexcept
{
    return qHash(reinterpret_cast<quintptr>(key), seed);
}
template<typename T> inline uint qHash(const T &t, uint seed)
    noexcept(noexcept(qHash(t)))
{ return qHash(t) ^ seed; }

namespace QtPrivate {

struct QHashCombine {
    typedef uint result_type;
    template <typename T>
    Q_DECL_CONSTEXPR result_type operator()(uint seed, const T &t) const noexcept(noexcept(qHash(t)))
    // combiner taken from N3876 / boost::hash_combine
    { return seed ^ (qHash(t) + 0x9e3779b9 + (seed << 6) + (seed >> 2)) ; }
};

struct QHashCombineCommutative {
    // QHashCombine is a good hash combiner, but is not commutative,
    // ie. it depends on the order of the input elements. That is
    // usually what we want: {0,1,3} should hash differently than
    // {1,3,0}. Except when it isn't (e.g. for QSet and
    // QHash). Therefore, provide a commutative combiner, too.
    typedef uint result_type;
    template <typename T>
    Q_DECL_CONSTEXPR result_type operator()(uint seed, const T &t) const noexcept(noexcept(qHash(t)))
    { return seed + qHash(t); } // don't use xor!
};

} // namespace QtPrivate

template <typename InputIterator>
inline uint qHashRange(InputIterator first, InputIterator last, uint seed = 0)
    noexcept(noexcept(qHash(*first))) // assume iterator operations don't throw
{
    return std::accumulate(first, last, seed, QtPrivate::QHashCombine());
}

template <typename InputIterator>
inline uint qHashRangeCommutative(InputIterator first, InputIterator last, uint seed = 0)
    noexcept(noexcept(qHash(*first))) // assume iterator operations don't throw
{
    return std::accumulate(first, last, seed, QtPrivate::QHashCombineCommutative());
}

template <typename T1, typename T2> inline uint qHash(const QPair<T1, T2> &key, uint seed = 0)
    noexcept(noexcept(qHash(key.first, seed)) && noexcept(qHash(key.second, seed)))
{
    uint h1 = qHash(key.first, seed);
    uint h2 = qHash(key.second, seed);
    return ((h1 << 16) | (h1 >> 16)) ^ h2 ^ seed;
}

template <typename T1, typename T2> inline uint qHash(const std::pair<T1, T2> &key, uint seed = 0)
    noexcept(noexcept(qHash(key.first, seed)) && noexcept(qHash(key.second, seed)))
{
    QtPrivate::QHashCombine hash;
    seed = hash(seed, key.first);
    seed = hash(seed, key.second);
    return seed;
}

#define QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH(Class, Arguments)      \
    QT_BEGIN_INCLUDE_NAMESPACE                                      \
    namespace std {                                                 \
        template <>                                                 \
        struct hash< QT_PREPEND_NAMESPACE(Class) > {                \
            using argument_type = QT_PREPEND_NAMESPACE(Class);      \
            using result_type = size_t;                             \
            size_t operator()(Arguments s) const                    \
                noexcept(noexcept(QT_PREPEND_NAMESPACE(qHash)(s)))  \
            {                                                       \
                /* this seeds qHash with the result of */           \
                /* std::hash applied to an int, to reap */          \
                /* any protection against predictable hash */       \
                /* values the std implementation may provide */     \
                return QT_PREPEND_NAMESPACE(qHash)(s,               \
                           QT_PREPEND_NAMESPACE(qHash)(             \
                                      std::hash<int>{}(0)));        \
            }                                                       \
        };                                                          \
    }                                                               \
    QT_END_INCLUDE_NAMESPACE                                        \
    /*end*/

#define QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(Class) \
    QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH(Class, const argument_type &)
#define QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_VALUE(Class) \
    QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH(Class, argument_type)

QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(QString)
QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(QStringRef)
QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_VALUE(QStringView)
QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_VALUE(QLatin1String)
QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(QByteArray)
QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(QBitArray)

QT_END_NAMESPACE

#if defined(Q_CC_MSVC)
#pragma warning( pop )
#endif

#endif // QHASHFUNCTIONS_H
