// ----------------------------------------------------------------------
// Copyright (c) 2016, Steven Gregory Popovitch - greg7mdp@gmail.com
// All rights reserved.
//
// Code derived derived from Boost libraries.
// Boost software licence reproduced below.
//
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
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// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// endorse or promote products derived from this software without
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// ---------------------------------------------------------------------------
// Boost Software License - Version 1.0 - August 17th, 2003
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
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// the above license grant, this restriction and the following disclaimer,
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// ---------------------------------------------------------------------------

//  ----------------------------------------------------------------------
//                  H A S H    F U N C T I O N S
//                  ----------------------------
//
//    Implements spp::spp_hash() and spp::hash_combine()
//  ----------------------------------------------------------------------

#if !defined(spp_utils_h_guard_)
#define spp_utils_h_guard_

#if defined(_MSC_VER)
    #if (_MSC_VER >= 1600 )                      // vs2010 (1900 is vs2015)
        #include <functional>
        #define SPP_HASH_CLASS std::hash
    #else
        #include  <hash_map>
        #define SPP_HASH_CLASS stdext::hash_compare
    #endif
    #if (_MSC_FULL_VER < 190021730)
        #define SPP_NO_CXX11_NOEXCEPT
    #endif
#elif defined __clang__
    #if __has_feature(cxx_noexcept)  // what to use here?
       #include <functional>
       #define SPP_HASH_CLASS  std::hash
    #else
       #include <tr1/unordered_map>
       #define SPP_HASH_CLASS std::tr1::hash
    #endif

    #if !__has_feature(cxx_noexcept)
        #define SPP_NO_CXX11_NOEXCEPT
    #endif
#elif defined(__GNUC__)
    #if defined(__GXX_EXPERIMENTAL_CXX0X__) || (__cplusplus >= 201103L)
        #include <functional>
        #define SPP_HASH_CLASS std::hash

        #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100) < 40600
            #define SPP_NO_CXX11_NOEXCEPT
        #endif
    #else
        #include <tr1/unordered_map>
        #define SPP_HASH_CLASS std::tr1::hash
        #define SPP_NO_CXX11_NOEXCEPT
    #endif
#else
    #include <functional>
    #define SPP_HASH_CLASS  std::hash
#endif

#ifdef SPP_NO_CXX11_NOEXCEPT
    #define SPP_NOEXCEPT
#else
    #define SPP_NOEXCEPT noexcept
#endif

#ifdef SPP_NO_CXX11_CONSTEXPR
    #define SPP_CONSTEXPR
#else
    #define SPP_CONSTEXPR constexpr
#endif

#define SPP_INLINE

#ifndef spp_
    #define spp_ spp
#endif

namespace spp_
{

template <class T>  T spp_min(T a, T b) { return a < b  ? a : b; }
template <class T>  T spp_max(T a, T b) { return a >= b ? a : b; }

template <class T>
struct spp_hash
{
    SPP_INLINE size_t operator()(const T &__v) const SPP_NOEXCEPT
    {
        SPP_HASH_CLASS<T> hasher;
        return hasher(__v);
    }
};

template <class T>
struct spp_hash<T *>
{
    static size_t spp_log2 (size_t val) SPP_NOEXCEPT
    {
        size_t res = 0;
        while (val > 1)
        {
            val >>= 1;
            res++;
        }
        return res;
    }

    SPP_INLINE size_t operator()(const T *__v) const SPP_NOEXCEPT
    {
        static const size_t shift = 3; // spp_log2(1 + sizeof(T)); // T might be incomplete!
        const uintptr_t i = (const uintptr_t)__v;
        return static_cast<size_t>(i >> shift);
    }
};

// from http://burtleburtle.net/bob/hash/integer.html
// fast and efficient for power of two table sizes where we always
// consider the last bits.
// ---------------------------------------------------------------
inline size_t spp_mix_32(uint32_t a)
{
    a = a ^ (a >> 4);
    a = (a ^ 0xdeadbeef) + (a << 5);
    a = a ^ (a >> 11);
    return static_cast<size_t>(a);
}

// Maybe we should do a more thorough scrambling as described in
// https://gist.github.com/badboy/6267743
// -------------------------------------------------------------
inline size_t spp_mix_64(uint64_t a)
{
    a = a ^ (a >> 4);
    a = (a ^ 0xdeadbeef) + (a << 5);
    a = a ^ (a >> 11);
    return (size_t)a;
}

template <>
struct spp_hash<bool> : public std::unary_function<bool, size_t>
{
    SPP_INLINE size_t operator()(bool __v) const SPP_NOEXCEPT
    { return static_cast<size_t>(__v); }
};

template <>
struct spp_hash<char> : public std::unary_function<char, size_t>
{
    SPP_INLINE size_t operator()(char __v) const SPP_NOEXCEPT
    { return static_cast<size_t>(__v); }
};

template <>
struct spp_hash<signed char> : public std::unary_function<signed char, size_t>
{
    SPP_INLINE size_t operator()(signed char __v) const SPP_NOEXCEPT
    { return static_cast<size_t>(__v); }
};

template <>
struct spp_hash<unsigned char> : public std::unary_function<unsigned char, size_t>
{
    SPP_INLINE size_t operator()(unsigned char __v) const SPP_NOEXCEPT
    { return static_cast<size_t>(__v); }
};

template <>
struct spp_hash<wchar_t> : public std::unary_function<wchar_t, size_t>
{
    SPP_INLINE size_t operator()(wchar_t __v) const SPP_NOEXCEPT
    { return static_cast<size_t>(__v); }
};

template <>
struct spp_hash<int16_t> : public std::unary_function<int16_t, size_t>
{
    SPP_INLINE size_t operator()(int16_t __v) const SPP_NOEXCEPT
    { return spp_mix_32(static_cast<uint32_t>(__v)); }
};

template <>
struct spp_hash<uint16_t> : public std::unary_function<uint16_t, size_t>
{
    SPP_INLINE size_t operator()(uint16_t __v) const SPP_NOEXCEPT
    { return spp_mix_32(static_cast<uint32_t>(__v)); }
};

template <>
struct spp_hash<int32_t> : public std::unary_function<int32_t, size_t>
{
    SPP_INLINE size_t operator()(int32_t __v) const SPP_NOEXCEPT
    { return spp_mix_32(static_cast<uint32_t>(__v)); }
};

template <>
struct spp_hash<uint32_t> : public std::unary_function<uint32_t, size_t>
{
    SPP_INLINE size_t operator()(uint32_t __v) const SPP_NOEXCEPT
    { return spp_mix_32(static_cast<uint32_t>(__v)); }
};

template <>
struct spp_hash<int64_t> : public std::unary_function<int64_t, size_t>
{
    SPP_INLINE size_t operator()(int64_t __v) const SPP_NOEXCEPT
    { return spp_mix_64(static_cast<uint64_t>(__v)); }
};

template <>
struct spp_hash<uint64_t> : public std::unary_function<uint64_t, size_t>
{
    SPP_INLINE size_t operator()(uint64_t __v) const SPP_NOEXCEPT
    { return spp_mix_64(static_cast<uint64_t>(__v)); }
};

template <>
struct spp_hash<float> : public std::unary_function<float, size_t>
{
    SPP_INLINE size_t operator()(float __v) const SPP_NOEXCEPT
    {
        // -0.0 and 0.0 should return same hash
        uint32_t *as_int = reinterpret_cast<uint32_t *>(&__v);
        return (__v == 0) ? static_cast<size_t>(0) : spp_mix_32(*as_int);
    }
};

template <>
struct spp_hash<double> : public std::unary_function<double, size_t>
{
    SPP_INLINE size_t operator()(double __v) const SPP_NOEXCEPT
    {
        // -0.0 and 0.0 should return same hash
        uint64_t *as_int = reinterpret_cast<uint64_t *>(&__v);
        return (__v == 0) ? static_cast<size_t>(0) : spp_mix_64(*as_int);
    }
};

template <class T, int sz> struct Combiner
{
    inline void operator()(T& seed, T value);
};

template <class T> struct Combiner<T, 4>
{
    inline void  operator()(T& seed, T value)
    {
        seed ^= value + 0x9e3779b9 + (seed << 6) + (seed >> 2);
    }
};

template <class T> struct Combiner<T, 8>
{
    inline void  operator()(T& seed, T value)
    {
        seed ^= value + T(0xc6a4a7935bd1e995) + (seed << 6) + (seed >> 2);
    }
};

template <class T>
inline void hash_combine(std::size_t& seed, T const& v)
{
    spp_::spp_hash<T> hasher;
    Combiner<std::size_t, sizeof(std::size_t)> combiner;

    combiner(seed, hasher(v));
}

static inline uint32_t s_spp_popcount_default(uint32_t i) SPP_NOEXCEPT
{
    i = i - ((i >> 1) & 0x55555555);
    i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
    return (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
}

static inline uint32_t s_spp_popcount_default(uint64_t x) SPP_NOEXCEPT
{
    const uint64_t m1  = uint64_t(0x5555555555555555); // binary: 0101...
    const uint64_t m2  = uint64_t(0x3333333333333333); // binary: 00110011..
    const uint64_t m4  = uint64_t(0x0f0f0f0f0f0f0f0f); // binary:  4 zeros,  4 ones ...
    const uint64_t h01 = uint64_t(0x0101010101010101); // the sum of 256 to the power of 0,1,2,3...

    x -= (x >> 1) & m1;             // put count of each 2 bits into those 2 bits
    x = (x & m2) + ((x >> 2) & m2); // put count of each 4 bits into those 4 bits 
    x = (x + (x >> 4)) & m4;        // put count of each 8 bits into those 8 bits 
    return (x * h01)>>56;           // returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24)+...
}

#ifdef __APPLE__
    static inline uint32_t count_trailing_zeroes(size_t v) SPP_NOEXCEPT
    {
        size_t x = (v & -v) - 1;
        // sadly sizeof() required to build on macos 
        return sizeof(size_t) == 8 ? s_spp_popcount_default((uint64_t)x) : s_spp_popcount_default((uint32_t)x);
    }

    static inline uint32_t s_popcount(size_t v) SPP_NOEXCEPT
    {
        // sadly sizeof() required to build on macos 
        return sizeof(size_t) == 8 ? s_spp_popcount_default((uint64_t)v) : s_spp_popcount_default((uint32_t)v);
    }
#else
    static inline uint32_t count_trailing_zeroes(size_t v) SPP_NOEXCEPT
    {
        return s_spp_popcount_default((v & -(intptr_t)v) - 1);
    }

    static inline uint32_t s_popcount(size_t v) SPP_NOEXCEPT
    {
        return s_spp_popcount_default(v);
    }
#endif

// -----------------------------------------------------------
// -----------------------------------------------------------
template<class T>
class libc_allocator
{
public:
    typedef T         value_type;
    typedef T*        pointer;
    typedef ptrdiff_t difference_type;
    typedef const T*  const_pointer;
    typedef size_t    size_type;

    libc_allocator() {}
    libc_allocator(const libc_allocator &) {}
    libc_allocator& operator=(const libc_allocator &) { return *this; }

#ifndef SPP_NO_CXX11_RVALUE_REFERENCES    
    libc_allocator(libc_allocator &&) {}
    libc_allocator& operator=(libc_allocator &&) { return *this; }
#endif

    pointer allocate(size_t n, const_pointer  /* unused */= 0) 
    {
        return static_cast<pointer>(malloc(n * sizeof(T)));
    }

    void deallocate(pointer p, size_t /* unused */) 
    {
        free(p);
    }

    pointer reallocate(pointer p, size_t new_size) 
    {
        return static_cast<pointer>(realloc(p, new_size * sizeof(T)));
    }

    // extra API to match spp_allocator interface
    pointer reallocate(pointer p, size_t /* old_size */, size_t new_size) 
    {
        return static_cast<pointer>(realloc(p, new_size * sizeof(T)));
    }

    size_type max_size() const
    {
        return static_cast<size_type>(-1) / sizeof(value_type);
    }

    void construct(pointer p, const value_type& val)
    {
        new(p) value_type(val);
    }

    void destroy(pointer p) { p->~value_type(); }

    template<class U>
    struct rebind
    {
        typedef spp_::libc_allocator<U> other;
    };

};

// forward declaration
// -------------------
template<class T>
class spp_allocator;

}

template<class T>
inline bool operator==(const spp_::libc_allocator<T> &, const spp_::libc_allocator<T> &)
{
    return true;
}

template<class T>
inline bool operator!=(const spp_::libc_allocator<T> &, const spp_::libc_allocator<T> &)
{
    return false;
}

#endif // spp_utils_h_guard_

