// SPDX-License-Identifier: LGPL-2.1+
/*
 * MurmurHash3 was written by Austin Appleby, and is placed in the public
 * domain. The author hereby disclaims copyright to this source code.
 *
 * Adapted by John Wiele (jwiele@redhat.com).
 */

#include "murmurhash3.h"

#include <linux/unaligned.h>

static inline u64 rotl64(u64 x, s8 r)
{
        return (x << r) | (x >> (64 - r));
}

#define ROTL64(x, y) rotl64(x, y)

/* Finalization mix - force all bits of a hash block to avalanche */

static __always_inline u64 fmix64(u64 k)
{
        k ^= k >> 33;
        k *= 0xff51afd7ed558ccdLLU;
        k ^= k >> 33;
        k *= 0xc4ceb9fe1a85ec53LLU;
        k ^= k >> 33;

        return k;
}

void murmurhash3_128(const void *key, const int len, const u32 seed, void *out)
{
        const u8 *data = key;
        const int nblocks = len / 16;

        u64 h1 = seed;
        u64 h2 = seed;

        const u64 c1 = 0x87c37b91114253d5LLU;
        const u64 c2 = 0x4cf5ad432745937fLLU;

        u64 *hash_out = out;

        /* body */
        int i;

        for (i = 0; i < nblocks; i++) {
                u64 k1 = get_unaligned_le64(&data[i * 16]);
                u64 k2 = get_unaligned_le64(&data[i * 16 + 8]);

                k1 *= c1;
                k1 = ROTL64(k1, 31);
                k1 *= c2;
                h1 ^= k1;

                h1 = ROTL64(h1, 27);
                h1 += h2;
                h1 = h1 * 5 + 0x52dce729;

                k2 *= c2;
                k2 = ROTL64(k2, 33);
                k2 *= c1;
                h2 ^= k2;

                h2 = ROTL64(h2, 31);
                h2 += h1;
                h2 = h2 * 5 + 0x38495ab5;
        }

        /* tail */

        {
                const u8 *tail = (const u8 *)(data + nblocks * 16);

                u64 k1 = 0;
                u64 k2 = 0;

                switch (len & 15) {
                case 15:
                        k2 ^= ((u64)tail[14]) << 48;
                        fallthrough;
                case 14:
                        k2 ^= ((u64)tail[13]) << 40;
                        fallthrough;
                case 13:
                        k2 ^= ((u64)tail[12]) << 32;
                        fallthrough;
                case 12:
                        k2 ^= ((u64)tail[11]) << 24;
                        fallthrough;
                case 11:
                        k2 ^= ((u64)tail[10]) << 16;
                        fallthrough;
                case 10:
                        k2 ^= ((u64)tail[9]) << 8;
                        fallthrough;
                case 9:
                        k2 ^= ((u64)tail[8]) << 0;
                        k2 *= c2;
                        k2 = ROTL64(k2, 33);
                        k2 *= c1;
                        h2 ^= k2;
                        fallthrough;

                case 8:
                        k1 ^= ((u64)tail[7]) << 56;
                        fallthrough;
                case 7:
                        k1 ^= ((u64)tail[6]) << 48;
                        fallthrough;
                case 6:
                        k1 ^= ((u64)tail[5]) << 40;
                        fallthrough;
                case 5:
                        k1 ^= ((u64)tail[4]) << 32;
                        fallthrough;
                case 4:
                        k1 ^= ((u64)tail[3]) << 24;
                        fallthrough;
                case 3:
                        k1 ^= ((u64)tail[2]) << 16;
                        fallthrough;
                case 2:
                        k1 ^= ((u64)tail[1]) << 8;
                        fallthrough;
                case 1:
                        k1 ^= ((u64)tail[0]) << 0;
                        k1 *= c1;
                        k1 = ROTL64(k1, 31);
                        k1 *= c2;
                        h1 ^= k1;
                        break;
                default:
                        break;
                }
        }
        /* finalization */

        h1 ^= len;
        h2 ^= len;

        h1 += h2;
        h2 += h1;

        h1 = fmix64(h1);
        h2 = fmix64(h2);

        h1 += h2;
        h2 += h1;

        put_unaligned_le64(h1, &hash_out[0]);
        put_unaligned_le64(h2, &hash_out[1]);
}