hxkey.hpp

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#pragma once
// SPDX-FileCopyrightText: © 2017-2026 Adrian Johnston.
// SPDX-License-Identifier: MIT
// This file is licensed under the MIT license found in the LICENSE.md file.

 
#include "libhatchet.h"
 
// HX_USE_MACROS_WITH_MODULE allows including macros alongside the module.
#if HX_USE_MACROS_WITH_MODULE
#error Header does not provide macros alone.
#endif
 
#include "hxutility.h"
 
HX_NS_BEGIN_

// Used for readability.
using hxcstring_const_ = const char*;
using hxcstring_ = char*;
 
#if HX_CPLUSPLUS >= 202002L
template<typename from_t_, typename to_t_>
concept hxconvertible_to = requires(from_t_ (&&from_)()) {
    requires requires { static_cast<to_t_>(from_()); };
};

template<typename from_t_, typename to_t_>
concept hxsame_as = hxis_same<from_t_, to_t_>::value;
#endif

template<typename A_, typename B_>
#if HX_CPLUSPLUS >= 202002L
requires requires(const A_& a_, const B_& b_) { { a_ == b_ } -> hxconvertible_to<bool>; }
#endif
hxattr_nodiscard hxinline hxattr_flatten  constexpr bool hxkey_equal(const A_& a_, const B_& b_) {
    return a_ == b_;
}

hxattr_nodiscard hxinline bool hxkey_equal(const hxcstring_const_& a_, const hxcstring_const_& b_) {
    return ::strcmp(a_, b_) == 0;
}
hxattr_nodiscard hxinline bool hxkey_equal(const hxcstring_const_& a_, const hxcstring_& b_) {
    return ::strcmp(a_, b_) == 0;
}
hxattr_nodiscard hxinline bool hxkey_equal(const hxcstring_& a_, const hxcstring_const_& b_) {
    return ::strcmp(a_, b_) == 0;
}
hxattr_nodiscard hxinline bool hxkey_equal(const hxcstring_& a_, const hxcstring_& b_) {
    return ::strcmp(a_, b_) == 0;
}

template<typename T_>
class hxkey_equal_t {
public:
    hxattr_nodiscard hxinline hxattr_flatten  constexpr bool operator()(const hxremove_cvref_t<T_>& a_,
            const hxremove_cvref_t<T_>& b_) const {
        return hxkey_equal(a_, b_);
    }
};

template<typename A_, typename B_>
#if HX_CPLUSPLUS >= 202002L
requires requires(const A_& a_, const B_& b_) { { a_ < b_ } -> hxconvertible_to<bool>; }
#endif
hxattr_nodiscard hxinline hxattr_flatten  constexpr bool hxkey_less(const A_& a_, const B_& b_) {
    return a_ < b_;
}

hxattr_nodiscard hxinline bool hxkey_less(const hxcstring_const_& a_, const hxcstring_const_& b_) {
    return ::strcmp(a_, b_) < 0;
}
hxattr_nodiscard hxinline bool hxkey_less(const hxcstring_const_& a_, const hxcstring_& b_) {
    return ::strcmp(a_, b_) < 0;
}
hxattr_nodiscard hxinline bool hxkey_less(const hxcstring_& a_, const hxcstring_const_& b_) {
    return ::strcmp(a_, b_) < 0;
}
hxattr_nodiscard hxinline bool hxkey_less(const hxcstring_& a_, const hxcstring_& b_) {
    return ::strcmp(a_, b_) < 0;
}

template<typename T_>
class hxkey_less_t {
public:
    hxattr_nodiscard hxinline hxattr_flatten  constexpr bool operator()(const hxremove_cvref_t<T_>& a_,
            const hxremove_cvref_t<T_>& b_) const {
        return hxkey_less(a_, b_);
    }
};

// xxhash32 prime constants and avalanche mixing. Useful when hashing sequential
// data. These are used by hxkey_hash overloads below.
hxinline_constexpr hxhash_t hxhash_prime1_ = hxhash_t{0x9E3779B1u};
hxinline_constexpr hxhash_t hxhash_prime2_ = hxhash_t{0x85EBCA77u};
hxinline_constexpr hxhash_t hxhash_prime3_ = hxhash_t{0xC2B2AE3Du};
hxinline_constexpr hxhash_t hxhash_prime4_ = hxhash_t{0x27D4EB2Fu};
hxinline_constexpr hxhash_t hxhash_prime5_ = hxhash_t{0x165667B1u};
 
// xxhash32 avalanche: x ^= x >> 15, x *= prime2, x ^= x >> 13, x *= prime3, x ^= x >> 16.
hxattr_nodiscard hxinline hxconstexpr hxhash_t hxhash_avalanche_(hxhash_t x_) {
    x_ ^= x_ >> 15u;
    x_ *= hxhash_prime2_;
    x_ ^= x_ >> 13u;
    x_ *= hxhash_prime3_;
    x_ ^= x_ >> 16u;
    return x_;
}

template<typename T_>
hxattr_nodiscard hxinline hxhash_t hxkey_hash(T_ x_) {
    // xxhash32 short-input path: seed=0, length=4, single 4-byte word.
    hxhash_t h_ = hxhash_prime5_ + hxhash_t{4u};
    // Did you write a custom hxkey_hash()?
    h_ += static_cast<hxhash_t>(x_) * hxhash_prime3_;
    h_  = ((h_ << 17u) | (h_ >> 15u)) * hxhash_prime4_;
    return hxhash_avalanche_(h_);
}

hxattr_nodiscard hxinline hxhash_t hxkey_hash(const char* s_) {
    hxhash_t h_ = hxhash_prime5_;
    while(*s_ != '\0') {
        h_ += static_cast<hxhash_t>(static_cast<unsigned char>(*s_++)) * hxhash_prime5_;
        h_ = ((h_ << 11u) | (h_ >> 21u)) * hxhash_prime1_;
    }
    return hxhash_avalanche_(h_);
}
 
HX_NS_END_