// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook
#include <features.h>

typedef unsigned int u32;

static __always_inline u32 rol32(u32 word, unsigned int shift)
{
        return (word << shift) | (word >> ((-shift) & 31));
}

#define __jhash_mix(a, b, c)                    \
{                                               \
        a -= c;  a ^= rol32(c, 4);  c += b;     \
        b -= a;  b ^= rol32(a, 6);  a += c;     \
        c -= b;  c ^= rol32(b, 8);  b += a;     \
        a -= c;  a ^= rol32(c, 16); c += b;     \
        b -= a;  b ^= rol32(a, 19); a += c;     \
        c -= b;  c ^= rol32(b, 4);  b += a;     \
}

#define __jhash_final(a, b, c)                  \
{                                               \
        c ^= b; c -= rol32(b, 14);              \
        a ^= c; a -= rol32(c, 11);              \
        b ^= a; b -= rol32(a, 25);              \
        c ^= b; c -= rol32(b, 16);              \
        a ^= c; a -= rol32(c, 4);               \
        b ^= a; b -= rol32(a, 14);              \
        c ^= b; c -= rol32(b, 24);              \
}

#define JHASH_INITVAL           0xdeadbeef

static ATTR
u32 jhash(const void *key, u32 length, u32 initval)
{
        u32 a, b, c;
        const unsigned char *k = key;

        a = b = c = JHASH_INITVAL + length + initval;

        while (length > 12) {
                a += *(volatile u32 *)(k);
                b += *(volatile u32 *)(k + 4);
                c += *(volatile u32 *)(k + 8);
                __jhash_mix(a, b, c);
                length -= 12;
                k += 12;
        }
        switch (length) {
        case 12: c += (u32)k[11]<<24;
        case 11: c += (u32)k[10]<<16;
        case 10: c += (u32)k[9]<<8;
        case 9:  c += k[8];
        case 8:  b += (u32)k[7]<<24;
        case 7:  b += (u32)k[6]<<16;
        case 6:  b += (u32)k[5]<<8;
        case 5:  b += k[4];
        case 4:  a += (u32)k[3]<<24;
        case 3:  a += (u32)k[2]<<16;
        case 2:  a += (u32)k[1]<<8;
        case 1:  a += k[0];
                 c ^= a;
                 __jhash_final(a, b, c);
        case 0: /* Nothing left to add */
                break;
        }

        return c;
}

static __always_inline u32 jhash2(const u32 *k, u32 length, u32 initval)
{
        u32 a, b, c;

        /* Set up the internal state */
        a = b = c = JHASH_INITVAL + (length<<2) + initval;

        /* Handle most of the key */
        while (length > 3) {
                a += k[0];
                b += k[1];
                c += k[2];
                __jhash_mix(a, b, c);
                length -= 3;
                k += 3;
        }

        /* Handle the last 3 u32's */
        switch (length) {
        case 3: c += k[2];
        case 2: b += k[1];
        case 1: a += k[0];
                __jhash_final(a, b, c);
                break;
        case 0: /* Nothing left to add */
                break;
        }

        return c;
}