hash.h

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#pragma once
 
#include "fl/stl/type_traits.h"
#include "fl/stl/int.h"
#include "fl/stl/compiler_control.h"
#include "fl/stl/bit_cast.h"
#include "fl/stl/string.h"
#include "fl/stl/noexcept.h"
#include "fl/stl/static_assert.h"
 
namespace fl {
 
template <typename T> struct vec2;
 
 
 
//-----------------------------------------------------------------------------
// MurmurHash3 x86 32-bit
//-----------------------------------------------------------------------------
// Based on the public‐domain implementation by Austin Appleby:
// https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
static inline u32 MurmurHash3_x86_32(const void *key, fl::size len,
                                          u32 seed = 0) {
 
    FL_DISABLE_WARNING_PUSH;
    FL_DISABLE_WARNING_IMPLICIT_FALLTHROUGH;
 
    const fl::u8 *data = static_cast<const fl::u8 *>(key);
    const int nblocks = int(len / 4);
 
    u32 h1 = seed;
    const u32 c1 = 0xcc9e2d51;
    const u32 c2 = 0x1b873593;
 
    // body
    const u32 *blocks = reinterpret_cast<const u32 *>(data); // ok reinterpret cast
    for (int i = 0; i < nblocks; ++i) {
        u32 k1 = blocks[i];
        k1 *= c1;
        k1 = (k1 << 15) | (k1 >> 17);
        k1 *= c2;
 
        h1 ^= k1;
        h1 = (h1 << 13) | (h1 >> 19);
        h1 = h1 * 5 + 0xe6546b64;
    }
 
    // tail
    const fl::u8 *tail = data + (nblocks * 4);
    u32 k1 = 0;
    switch (len & 3) {
    case 3:
        k1 ^= u32(tail[2]) << 16;
    case 2:
        k1 ^= u32(tail[1]) << 8;
    case 1:
        k1 ^= u32(tail[0]);
        k1 *= c1;
        k1 = (k1 << 15) | (k1 >> 17);
        k1 *= c2;
        h1 ^= k1;
    }
 
    // finalization
    h1 ^= u32(len);
    // fmix32
    h1 ^= h1 >> 16;
    h1 *= 0x85ebca6b;
    h1 ^= h1 >> 13;
    h1 *= 0xc2b2ae35;
    h1 ^= h1 >> 16;
 
    return h1;
 
    FL_DISABLE_WARNING_POP;
}
 
//-----------------------------------------------------------------------------
// Fast, cheap 32-bit integer hash (Thomas Wang)
//-----------------------------------------------------------------------------
static inline u32 fast_hash32(u32 x) FL_NOEXCEPT {
    x = (x ^ 61u) ^ (x >> 16);
    x = x + (x << 3);
    x = x ^ (x >> 4);
    x = x * 0x27d4eb2dU;
    x = x ^ (x >> 15);
    return x;
}
 
// 3) Handy two-word hasher
static inline u32 hash_pair(u32 a, u32 b,
                                 u32 seed = 0) FL_NOEXCEPT {
    // mix in 'a', then mix in 'b'
    u32 h = fast_hash32(seed ^ a);
    return fast_hash32(h ^ b);
}
 
static inline u32 fast_hash64(u64 x) FL_NOEXCEPT {
    u32 x1 = static_cast<u32>(x & 0x00000000FFFFFFFF);
    u32 x2 = static_cast<u32>(x >> 32);
    return hash_pair(x1, x2);
}
 
//-----------------------------------------------------------------------------
// Functor for hashing arbitrary byte‐ranges to a 32‐bit value
//-----------------------------------------------------------------------------
// https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
template <typename T> struct Hash {
    FL_STATIC_ASSERT(fl::is_pod<T>::value,
                  "fl::Hash<T> only supports POD types (integrals, floats, "
                  "etc.), you need to define your own hash.");
    u32 operator()(const T &key) const FL_NOEXCEPT {
        return MurmurHash3_x86_32(&key, sizeof(T));
    }
};
 
template <typename T> struct FastHash {
    FL_STATIC_ASSERT(fl::is_pod<T>::value,
                  "fl::FastHash<T> only supports POD types (integrals, floats, "
                  "etc.), you need to define your own hash.");
    u32 operator()(const T &key) const FL_NOEXCEPT {
        return fast_hash32(key);
    }
};
 
template <typename T> struct FastHash<vec2<T>> {
    u32 operator()(const vec2<T> &key) const FL_NOEXCEPT {
        if (sizeof(T) == sizeof(fl::u8)) {
            u32 x = static_cast<u32>(key.x) +
                         (static_cast<u32>(key.y) << 8);
            return fast_hash32(x);
        }
        if (sizeof(T) == sizeof(u16)) {
            u32 x = static_cast<u32>(key.x) +
                         (static_cast<u32>(key.y) << 16);
            return fast_hash32(x);
        }
        if (sizeof(T) == sizeof(u32)) {
            return hash_pair(key.x, key.y);
        }
        return MurmurHash3_x86_32(&key, sizeof(T));
    }
};
 
template <typename T> struct Hash<T *> {
    u32 operator()(T *key) const FL_NOEXCEPT {
        if (sizeof(T *) == sizeof(u32)) {
            u32 key_u = static_cast<u32>(fl::ptr_to_int(key));
            return fast_hash32(key_u);
        } else {
            // Hash the pointer value (address), not the data it points to
            return MurmurHash3_x86_32(&key, sizeof(T *));
        }
    }
};
 
template <typename T> struct Hash<vec2<T>> {
    u32 operator()(const vec2<T> &key) const FL_NOEXCEPT {
FL_DISABLE_WARNING_PUSH
FL_DISABLE_WARNING_MAYBE_UNINITIALIZED
        T packed[2] = {key.x, key.y};
        const void *p = &packed[0];
        return MurmurHash3_x86_32(p, sizeof(packed));
FL_DISABLE_WARNING_POP
    }
};
 
template <typename T> struct Hash<fl::shared_ptr<T>> {
    u32 operator()(const fl::shared_ptr<T> &key) const FL_NOEXCEPT {
        auto hasher = Hash<T *>();
        return hasher(key.get());
    }
};
 
template<> struct Hash<float> {
    u32 operator()(const float key) const FL_NOEXCEPT {
        u32 ikey = fl::bit_cast<u32>(key);
        return fast_hash32(ikey);
    }
};
 
template<> struct Hash<double> {
    u32 operator()(const double& key) const FL_NOEXCEPT {
        return MurmurHash3_x86_32(&key, sizeof(double));
    }
};
 
template<> struct Hash<i32> {
    u32 operator()(const i32 key) const FL_NOEXCEPT {
        u32 ukey = static_cast<u32>(key);
        return fast_hash32(ukey);
    }
};
 
template<> struct Hash<bool> {
    u32 operator()(const bool key) const FL_NOEXCEPT {
        return fast_hash32(key);
    }
};
 
template<> struct Hash<fl::u8> {
    u32 operator()(const fl::u8 &key) const FL_NOEXCEPT {
        return fast_hash32(key);
    }
};
 
template<> struct Hash<u16> {
    u32 operator()(const u16 &key) const FL_NOEXCEPT {
        return fast_hash32(key);
    }
};
 
template<> struct Hash<u32> {
    u32 operator()(const u32 &key) const FL_NOEXCEPT {
        return fast_hash32(key);
    }
};
 
template<> struct Hash<i8> {
    u32 operator()(const i8 &key) const FL_NOEXCEPT {
        u8 v = static_cast<u8>(key);
        return fast_hash32(v);
    }
};
 
template<> struct Hash<i16> {
    u32 operator()(const i16 &key) const FL_NOEXCEPT {
        u16 ukey = static_cast<u16>(key);
        return fast_hash32(ukey);
    }
};
 
// FASTLED_DEFINE_FAST_HASH(fl::u8)
// FASTLED_DEFINE_FAST_HASH(u16)
// FASTLED_DEFINE_FAST_HASH(u32)
// FASTLED_DEFINE_FAST_HASH(i8)
// FASTLED_DEFINE_FAST_HASH(i16)
// FASTLED_DEFINE_FAST_HASH(bool)
 
// FASTLED_DEFINE_FAST_HASH(int)
 
//-----------------------------------------------------------------------------
// Convenience for string types → u32
//----------------------------------------------------------------------------
template <> struct Hash<fl::string> {
    u32 operator()(const fl::string &key) const FL_NOEXCEPT {
        return MurmurHash3_x86_32(key.data(), key.size());
    }
};
 
template <> struct Hash<fl::string_view> {
    u32 operator()(const fl::string_view& sv) const FL_NOEXCEPT {
        return MurmurHash3_x86_32(sv.data(), sv.size());
    }
};
 
 
 
} // namespace fl