hash.c

  1// SPDX-License-Identifier: GPL-2.0
  2#ifdef __KERNEL__
  3# include <linux/crush/hash.h>
  4#else
  5# include "hash.h"
  6#endif
  7
  8/*
  9 * Robert Jenkins' function for mixing 32-bit values
 10 * https://burtleburtle.net/bob/hash/evahash.html
 11 * a, b = random bits, c = input and output
 12 */
 13#define crush_hashmix(a, b, c) do {			\
 14		a = a-b;  a = a-c;  a = a^(c>>13);	\
 15		b = b-c;  b = b-a;  b = b^(a<<8);	\
 16		c = c-a;  c = c-b;  c = c^(b>>13);	\
 17		a = a-b;  a = a-c;  a = a^(c>>12);	\
 18		b = b-c;  b = b-a;  b = b^(a<<16);	\
 19		c = c-a;  c = c-b;  c = c^(b>>5);	\
 20		a = a-b;  a = a-c;  a = a^(c>>3);	\
 21		b = b-c;  b = b-a;  b = b^(a<<10);	\
 22		c = c-a;  c = c-b;  c = c^(b>>15);	\
 23	} while (0)
 24
 25#define crush_hash_seed 1315423911
 26
 27static __u32 crush_hash32_rjenkins1(__u32 a)
 28{
 29	__u32 hash = crush_hash_seed ^ a;
 30	__u32 b = a;
 31	__u32 x = 231232;
 32	__u32 y = 1232;
 33	crush_hashmix(b, x, hash);
 34	crush_hashmix(y, a, hash);
 35	return hash;
 36}
 37
 38static __u32 crush_hash32_rjenkins1_2(__u32 a, __u32 b)
 39{
 40	__u32 hash = crush_hash_seed ^ a ^ b;
 41	__u32 x = 231232;
 42	__u32 y = 1232;
 43	crush_hashmix(a, b, hash);
 44	crush_hashmix(x, a, hash);
 45	crush_hashmix(b, y, hash);
 46	return hash;
 47}
 48
 49static __u32 crush_hash32_rjenkins1_3(__u32 a, __u32 b, __u32 c)
 50{
 51	__u32 hash = crush_hash_seed ^ a ^ b ^ c;
 52	__u32 x = 231232;
 53	__u32 y = 1232;
 54	crush_hashmix(a, b, hash);
 55	crush_hashmix(c, x, hash);
 56	crush_hashmix(y, a, hash);
 57	crush_hashmix(b, x, hash);
 58	crush_hashmix(y, c, hash);
 59	return hash;
 60}
 61
 62static __u32 crush_hash32_rjenkins1_4(__u32 a, __u32 b, __u32 c, __u32 d)
 63{
 64	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d;
 65	__u32 x = 231232;
 66	__u32 y = 1232;
 67	crush_hashmix(a, b, hash);
 68	crush_hashmix(c, d, hash);
 69	crush_hashmix(a, x, hash);
 70	crush_hashmix(y, b, hash);
 71	crush_hashmix(c, x, hash);
 72	crush_hashmix(y, d, hash);
 73	return hash;
 74}
 75
 76static __u32 crush_hash32_rjenkins1_5(__u32 a, __u32 b, __u32 c, __u32 d,
 77				      __u32 e)
 78{
 79	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e;
 80	__u32 x = 231232;
 81	__u32 y = 1232;
 82	crush_hashmix(a, b, hash);
 83	crush_hashmix(c, d, hash);
 84	crush_hashmix(e, x, hash);
 85	crush_hashmix(y, a, hash);
 86	crush_hashmix(b, x, hash);
 87	crush_hashmix(y, c, hash);
 88	crush_hashmix(d, x, hash);
 89	crush_hashmix(y, e, hash);
 90	return hash;
 91}
 92
 93
 94__u32 crush_hash32(int type, __u32 a)
 95{
 96	switch (type) {
 97	case CRUSH_HASH_RJENKINS1:
 98		return crush_hash32_rjenkins1(a);
 99	default:
100		return 0;
101	}
102}
103
104__u32 crush_hash32_2(int type, __u32 a, __u32 b)
105{
106	switch (type) {
107	case CRUSH_HASH_RJENKINS1:
108		return crush_hash32_rjenkins1_2(a, b);
109	default:
110		return 0;
111	}
112}
113
114__u32 crush_hash32_3(int type, __u32 a, __u32 b, __u32 c)
115{
116	switch (type) {
117	case CRUSH_HASH_RJENKINS1:
118		return crush_hash32_rjenkins1_3(a, b, c);
119	default:
120		return 0;
121	}
122}
123
124__u32 crush_hash32_4(int type, __u32 a, __u32 b, __u32 c, __u32 d)
125{
126	switch (type) {
127	case CRUSH_HASH_RJENKINS1:
128		return crush_hash32_rjenkins1_4(a, b, c, d);
129	default:
130		return 0;
131	}
132}
133
134__u32 crush_hash32_5(int type, __u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
135{
136	switch (type) {
137	case CRUSH_HASH_RJENKINS1:
138		return crush_hash32_rjenkins1_5(a, b, c, d, e);
139	default:
140		return 0;
141	}
142}
143
144const char *crush_hash_name(int type)
145{
146	switch (type) {
147	case CRUSH_HASH_RJENKINS1:
148		return "rjenkins1";
149	default:
150		return "unknown";
151	}
152}