219 lines
6.3 KiB
C
219 lines
6.3 KiB
C
// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd
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//
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// SPDX-License-Identifier: LGPL-2.1
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#ifndef _LINUX_JHASH_H
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#define _LINUX_JHASH_H
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#include "types.h"
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/* Best hash sizes are of power of two */
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#define jhash_size(n) ((u32)1 << (n))
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/* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */
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#define jhash_mask(n) (jhash_size(n) - 1)
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static inline u32 rol32(u32 word, unsigned int shift)
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{
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return (word << shift) | (word >> ((-shift) & 31));
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}
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static inline u32 __get_unaligned_cpu32(const void *p)
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{
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const u32 *ptr = (const u32 *)p;
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return *ptr;
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}
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/* __jhash_mix -- mix 3 32-bit values reversibly. */
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#define __jhash_mix(a, b, c) \
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{ \
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a -= c; \
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a ^= rol32(c, 4); \
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c += b; \
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b -= a; \
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b ^= rol32(a, 6); \
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a += c; \
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c -= b; \
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c ^= rol32(b, 8); \
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b += a; \
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a -= c; \
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a ^= rol32(c, 16); \
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c += b; \
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b -= a; \
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b ^= rol32(a, 19); \
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a += c; \
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c -= b; \
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c ^= rol32(b, 4); \
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b += a; \
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}
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/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
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#define __jhash_final(a, b, c) \
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{ \
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c ^= b; \
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c -= rol32(b, 14); \
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a ^= c; \
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a -= rol32(c, 11); \
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b ^= a; \
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b -= rol32(a, 25); \
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c ^= b; \
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c -= rol32(b, 16); \
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a ^= c; \
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a -= rol32(c, 4); \
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b ^= a; \
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b -= rol32(a, 14); \
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c ^= b; \
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c -= rol32(b, 24); \
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}
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/* An arbitrary initial parameter */
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#define JHASH_INITVAL 0xdeadbeef
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/* jhash - hash an arbitrary key
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* @k: sequence of bytes as key
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* @length: the length of the key
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* @initval: the previous hash, or an arbitray value
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*
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* The generic version, hashes an arbitrary sequence of bytes.
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* No alignment or length assumptions are made about the input key.
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*
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* Returns the hash value of the key. The result depends on endianness.
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*/
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static inline u32 jhash(const void *key, u32 length, u32 initval)
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{
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u32 a, b, c;
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const u8 *k = (typeof(k))key;
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/* Set up the internal state */
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a = b = c = JHASH_INITVAL + length + initval;
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/* All but the last block: affect some 32 bits of (a,b,c) */
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while (length > 12)
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{
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a += __get_unaligned_cpu32(k);
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b += __get_unaligned_cpu32(k + 4);
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c += __get_unaligned_cpu32(k + 8);
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__jhash_mix(a, b, c);
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length -= 12;
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k += 12;
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}
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/* Last block: affect all 32 bits of (c) */
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switch (length)
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{
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case 12:
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c += (u32)k[11] << 24;
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fallthrough;
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case 11:
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c += (u32)k[10] << 16;
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fallthrough;
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case 10:
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c += (u32)k[9] << 8;
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fallthrough;
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case 9:
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c += k[8];
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fallthrough;
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case 8:
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b += (u32)k[7] << 24;
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fallthrough;
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case 7:
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b += (u32)k[6] << 16;
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fallthrough;
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case 6:
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b += (u32)k[5] << 8;
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fallthrough;
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case 5:
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b += k[4];
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fallthrough;
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case 4:
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a += (u32)k[3] << 24;
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fallthrough;
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case 3:
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a += (u32)k[2] << 16;
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fallthrough;
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case 2:
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a += (u32)k[1] << 8;
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fallthrough;
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case 1:
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a += k[0];
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__jhash_final(a, b, c);
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break;
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case 0: /* Nothing left to add */
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break;
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}
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return c;
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}
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/* jhash2 - hash an array of u32's
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* @k: the key which must be an array of u32's
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* @length: the number of u32's in the key
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* @initval: the previous hash, or an arbitray value
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*
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* Returns the hash value of the key.
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*/
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static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
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{
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u32 a, b, c;
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/* Set up the internal state */
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a = b = c = JHASH_INITVAL + (length << 2) + initval;
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/* Handle most of the key */
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while (length > 3)
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{
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a += k[0];
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b += k[1];
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c += k[2];
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__jhash_mix(a, b, c);
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length -= 3;
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k += 3;
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}
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/* Handle the last 3 u32's */
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switch (length)
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{
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case 3:
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c += k[2];
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fallthrough;
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case 2:
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b += k[1];
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fallthrough;
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case 1:
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a += k[0];
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__jhash_final(a, b, c);
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break;
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case 0: /* Nothing left to add */
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break;
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}
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return c;
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}
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/* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */
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static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
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{
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a += initval;
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b += initval;
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c += initval;
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__jhash_final(a, b, c);
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return c;
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}
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static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
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{
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return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2));
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}
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static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
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{
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return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
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}
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static inline u32 jhash_1word(u32 a, u32 initval)
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{
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return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2));
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}
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#endif /* _LINUX_JHASH_H */
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