rte_jhash.h

Go to the documentation of this file.

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2015 Intel Corporation.
 */

#ifndef _RTE_JHASH_H
#define _RTE_JHASH_H

#ifdef __cplusplus
extern "C" {
#endif

#include <stdint.h>
#include <string.h>
#include <limits.h>

#include <rte_config.h>
#include <rte_log.h>
#include <rte_byteorder.h>

/* jhash.h: Jenkins hash support.
 *
 * Copyright (C) 2006 Bob Jenkins (bob_jenkins@burtleburtle.net)
 *
 * http://burtleburtle.net/bob/hash/
 *
 * These are the credits from Bob's sources:
 *
 * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
 *
 * These are functions for producing 32-bit hashes for hash table lookup.
 * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
 * 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's in
 * the public domain.  It has no warranty.
 *
 * $FreeBSD$
 */

#define rot(x, k) (((x) << (k)) | ((x) >> (32-(k))))

#define __rte_jhash_mix(a, b, c) do { \
    a -= c; a ^= rot(c, 4); c += b; \
    b -= a; b ^= rot(a, 6); a += c; \
    c -= b; c ^= rot(b, 8); b += a; \
    a -= c; a ^= rot(c, 16); c += b; \
    b -= a; b ^= rot(a, 19); a += c; \
    c -= b; c ^= rot(b, 4); b += a; \
} while (0)

#define __rte_jhash_final(a, b, c) do { \
    c ^= b; c -= rot(b, 14); \
    a ^= c; a -= rot(c, 11); \
    b ^= a; b -= rot(a, 25); \
    c ^= b; c -= rot(b, 16); \
    a ^= c; a -= rot(c, 4);  \
    b ^= a; b -= rot(a, 14); \
    c ^= b; c -= rot(b, 24); \
} while (0)

#define RTE_JHASH_GOLDEN_RATIO      0xdeadbeef

#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
#define BIT_SHIFT(x, y, k) (((x) >> (k)) | ((uint64_t)(y) << (32-(k))))
#else
#define BIT_SHIFT(x, y, k) (((uint64_t)(x) << (k)) | ((y) >> (32-(k))))
#endif

#define LOWER8b_MASK rte_le_to_cpu_32(0xff)
#define LOWER16b_MASK rte_le_to_cpu_32(0xffff)
#define LOWER24b_MASK rte_le_to_cpu_32(0xffffff)

static inline void
__rte_jhash_2hashes(const void *key, uint32_t length, uint32_t *pc,
        uint32_t *pb, unsigned check_align)
{
    uint32_t a, b, c;

    /* Set up the internal state */
    a = b = c = RTE_JHASH_GOLDEN_RATIO + ((uint32_t)length) + *pc;
    c += *pb;

    /*
     * Check key alignment. For x86 architecture, first case is always optimal
     * If check_align is not set, first case will be used
     */
#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686) || defined(RTE_ARCH_X86_X32)
    const uint32_t *k = (const uint32_t *)key;
    const uint32_t s = 0;
#else
    const uint32_t *k = (uint32_t *)((uintptr_t)key & (uintptr_t)~3);
    const uint32_t s = ((uintptr_t)key & 3) * CHAR_BIT;
#endif
    if (!check_align || s == 0) {
        while (length > 12) {
            a += k[0];
            b += k[1];
            c += k[2];

            __rte_jhash_mix(a, b, c);

            k += 3;
            length -= 12;
        }

        switch (length) {
        case 12:
            c += k[2]; b += k[1]; a += k[0]; break;
        case 11:
            c += k[2] & LOWER24b_MASK; b += k[1]; a += k[0]; break;
        case 10:
            c += k[2] & LOWER16b_MASK; b += k[1]; a += k[0]; break;
        case 9:
            c += k[2] & LOWER8b_MASK; b += k[1]; a += k[0]; break;
        case 8:
            b += k[1]; a += k[0]; break;
        case 7:
            b += k[1] & LOWER24b_MASK; a += k[0]; break;
        case 6:
            b += k[1] & LOWER16b_MASK; a += k[0]; break;
        case 5:
            b += k[1] & LOWER8b_MASK; a += k[0]; break;
        case 4:
            a += k[0]; break;
        case 3:
            a += k[0] & LOWER24b_MASK; break;
        case 2:
            a += k[0] & LOWER16b_MASK; break;
        case 1:
            a += k[0] & LOWER8b_MASK; break;
        /* zero length strings require no mixing */
        case 0:
            *pc = c;
            *pb = b;
            return;
        };
    } else {
        /* all but the last block: affect some 32 bits of (a, b, c) */
        while (length > 12) {
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            c += BIT_SHIFT(k[2], k[3], s);
            __rte_jhash_mix(a, b, c);

            k += 3;
            length -= 12;
        }

        /* last block: affect all 32 bits of (c) */
        switch (length) {
        case 12:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            c += BIT_SHIFT(k[2], k[3], s);
            break;
        case 11:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            c += BIT_SHIFT(k[2], k[3], s) & LOWER24b_MASK;
            break;
        case 10:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            c += BIT_SHIFT(k[2], k[3], s) & LOWER16b_MASK;
            break;
        case 9:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            c += BIT_SHIFT(k[2], k[3], s) & LOWER8b_MASK;
            break;
        case 8:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s);
            break;
        case 7:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s) & LOWER24b_MASK;
            break;
        case 6:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s) & LOWER16b_MASK;
            break;
        case 5:
            a += BIT_SHIFT(k[0], k[1], s);
            b += BIT_SHIFT(k[1], k[2], s) & LOWER8b_MASK;
            break;
        case 4:
            a += BIT_SHIFT(k[0], k[1], s);
            break;
        case 3:
            a += BIT_SHIFT(k[0], k[1], s) & LOWER24b_MASK;
            break;
        case 2:
            a += BIT_SHIFT(k[0], k[1], s) & LOWER16b_MASK;
            break;
        case 1:
            a += BIT_SHIFT(k[0], k[1], s) & LOWER8b_MASK;
            break;
        /* zero length strings require no mixing */
        case 0:
            *pc = c;
            *pb = b;
            return;
        }
    }

    __rte_jhash_final(a, b, c);

    *pc = c;
    *pb = b;
}

static inline void
rte_jhash_2hashes(const void *key, uint32_t length, uint32_t *pc, uint32_t *pb)
{
    __rte_jhash_2hashes(key, length, pc, pb, 1);
}

static inline void
rte_jhash_32b_2hashes(const uint32_t *k, uint32_t length, uint32_t *pc, uint32_t *pb)
{
    __rte_jhash_2hashes((const void *) k, (length << 2), pc, pb, 0);
}

static inline uint32_t
rte_jhash(const void *key, uint32_t length, uint32_t initval)
{
    uint32_t initval2 = 0;

    rte_jhash_2hashes(key, length, &initval, &initval2);

    return initval;
}

static inline uint32_t
rte_jhash_32b(const uint32_t *k, uint32_t length, uint32_t initval)
{
    uint32_t initval2 = 0;

    rte_jhash_32b_2hashes(k, length, &initval, &initval2);

    return initval;
}

static inline uint32_t
__rte_jhash_3words(uint32_t a, uint32_t b, uint32_t c, uint32_t initval)
{
    a += RTE_JHASH_GOLDEN_RATIO + initval;
    b += RTE_JHASH_GOLDEN_RATIO + initval;
    c += RTE_JHASH_GOLDEN_RATIO + initval;

    __rte_jhash_final(a, b, c);

    return c;
}

static inline uint32_t
rte_jhash_3words(uint32_t a, uint32_t b, uint32_t c, uint32_t initval)
{
    return __rte_jhash_3words(a + 12, b + 12, c + 12, initval);
}

static inline uint32_t
rte_jhash_2words(uint32_t a, uint32_t b, uint32_t initval)
{
    return __rte_jhash_3words(a + 8, b + 8, 8, initval);
}

static inline uint32_t
rte_jhash_1word(uint32_t a, uint32_t initval)
{
    return __rte_jhash_3words(a + 4, 4, 4, initval);
}

#ifdef __cplusplus
}
#endif

#endif /* _RTE_JHASH_H */