/* IBM_PROLOG_BEGIN_TAG                                                   */
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/* $Source: import/chips/p9/procedures/ppe/tools/ppetracepp/jhash.h $     */
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/* OpenPOWER HCODE Project                                                */
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/* IBM_PROLOG_END_TAG                                                     */
#ifndef _LINUX_JHASH_H
#define _LINUX_JHASH_H

/* jhash.h: Jenkins hash support.
 *
 * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
 *
 * http://burtleburtle.net/bob/hash/
 *
 * These are the credits from Bob's sources:
 *
 * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
 * hash(), hash2(), hash3, and mix() are externally useful functions.
 * Routines to test the hash are included if SELF_TEST is defined.
 * You can use this free for any purpose.  It has no warranty.
 *
 * Copyright (C) 2003 David S. Miller (davem@redhat.com)
 *
 * I've modified Bob's hash to be useful in the Linux kernel, and
 * any bugs present are surely my fault.  -DaveM
 */

/* NOTE: Arguments are modified. */
#define __jhash_mix(a, b, c) \
    { \
        a -= b; a -= c; a ^= (c>>13); \
        b -= c; b -= a; b ^= (a<<8); \
        c -= a; c -= b; c ^= (b>>13); \
        a -= b; a -= c; a ^= (c>>12);  \
        b -= c; b -= a; b ^= (a<<16); \
        c -= a; c -= b; c ^= (b>>5); \
        a -= b; a -= c; a ^= (c>>3);  \
        b -= c; b -= a; b ^= (a<<10); \
        c -= a; c -= b; c ^= (b>>15); \
    }

/* The golden ration: an arbitrary value */
#define JHASH_GOLDEN_RATIO  0x9e3779b9

/* The most generic version, hashes an arbitrary sequence
 * of bytes.  No alignment or length assumptions are made about
 * the input key.
 */
static inline u32 jhash(const void* key, u32 length, u32 initval)
{
    u32 a, b, c, len;
    const u8* k = (const u8*)key;

    len = length;
    a = b = JHASH_GOLDEN_RATIO;
    c = initval;

    while (len >= 12)
    {
        a += (k[0] + ((u32)k[1] << 8) + ((u32)k[2] << 16) + ((u32)k[3] << 24));
        b += (k[4] + ((u32)k[5] << 8) + ((u32)k[6] << 16) + ((u32)k[7] << 24));
        c += (k[8] + ((u32)k[9] << 8) + ((u32)k[10] << 16) + ((u32)k[11] << 24));

        __jhash_mix(a, b, c);

        k += 12;
        len -= 12;
    }

    c += length;

    switch (len)
    {
        case 11:
            c += ((u32)k[10] << 24);

        case 10:
            c += ((u32)k[9] << 16);

        case 9 :
            c += ((u32)k[8] << 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];
    };

    __jhash_mix(a, b, c);

    return c;
}

/* A special optimized version that handles 1 or more of u32s.
 * The length parameter here is the number of u32s in the key.
 */
static inline u32 jhash2(const u32* k, u32 length, u32 initval)
{
    u32 a, b, c, len;

    a = b = JHASH_GOLDEN_RATIO;
    c = initval;
    len = length;

    while (len >= 3)
    {
        a += k[0];
        b += k[1];
        c += k[2];
        __jhash_mix(a, b, c);
        k += 3;
        len -= 3;
    }

    c += length * 4;

    switch (len)
    {
        case 2 :
            b += k[1];

        case 1 :
            a += k[0];
    };

    __jhash_mix(a, b, c);

    return c;
}


/* A special ultra-optimized versions that knows they are hashing exactly
 * 3, 2 or 1 word(s).
 *
 * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
 *       done at the end is not done here.
 */
static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
{
    a += JHASH_GOLDEN_RATIO;
    b += JHASH_GOLDEN_RATIO;
    c += initval;

    __jhash_mix(a, b, c);

    return c;
}

static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
{
    return jhash_3words(a, b, 0, initval);
}

static inline u32 jhash_1word(u32 a, u32 initval)
{
    return jhash_3words(a, 0, 0, initval);
}

#endif /* _LINUX_JHASH_H */
