serenity/AK/HashFunctions.h

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT HOLDER OR 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 <AK/Types.h>

constexpr unsigned int_hash(u32 key)
{
    key += ~(key << 15);
    key ^= (key >> 10);
    key += (key << 3);
    key ^= (key >> 6);
    key += ~(key << 11);
    key ^= (key >> 16);
    return key;
}

constexpr unsigned double_hash(u32 key)
{
    key = ~key + (key >> 23);
    key ^= (key << 12);
    key ^= (key >> 7);
    key ^= (key << 2);
    key ^= (key >> 20);
    return key;
}

constexpr unsigned pair_int_hash(u32 key1, u32 key2)
{
    return int_hash((int_hash(key1) * 209) ^ (int_hash(key2 * 413)));
}

constexpr unsigned u64_hash(u64 key)
{
    u32 first = key & 0xFFFFFFFF;
    u32 last = key >> 32;
    return pair_int_hash(first, last);
}

constexpr unsigned ptr_hash(FlatPtr ptr)
{
    if constexpr (sizeof(ptr) == 8)
        return u64_hash(ptr);
    else
        return int_hash(ptr);
}

inline unsigned ptr_hash(const void* ptr)
{
    return ptr_hash(FlatPtr(ptr));
}