6  * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
12  * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
14  * These are functions for producing 32-bit hashes for hash table lookup.
20  * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
32 #define jhash_mask(n)   (jhash_size(n)-1)
34 /* __jhash_mix -- mix 3 32-bit values reversibly. */
35 #define __jhash_mix(a, b, c)			\  argument
37 	a -= c;  a ^= rol32(c, 4);  c += b;	\
38 	b -= a;  b ^= rol32(a, 6);  a += c;	\
39 	c -= b;  c ^= rol32(b, 8);  b += a;	\
40 	a -= c;  a ^= rol32(c, 16); c += b;	\
41 	b -= a;  b ^= rol32(a, 19); a += c;	\
42 	c -= b;  c ^= rol32(b, 4);  b += a;	\
45 /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
46 #define __jhash_final(a, b, c)			\  argument
48 	c ^= b; c -= rol32(b, 14);		\
49 	a ^= c; a -= rol32(c, 11);		\
50 	b ^= a; b -= rol32(a, 25);		\
51 	c ^= b; c -= rol32(b, 16);		\
52 	a ^= c; a -= rol32(c, 4);		\
53 	b ^= a; b -= rol32(a, 14);		\
54 	c ^= b; c -= rol32(b, 24);		\
60 /* jhash - hash an arbitrary key
72 	u32 a, b, c;  in jhash()  local
76 	a = b = c = JHASH_INITVAL + length + initval;  in jhash()
78 	/* All but the last block: affect some 32 bits of (a,b,c) */  in jhash()
80 		a += __get_unaligned_cpu32(k);  in jhash()
82 		c += __get_unaligned_cpu32(k + 8);  in jhash()
83 		__jhash_mix(a, b, c);  in jhash()
84 		length -= 12;  in jhash()
87 	/* Last block: affect all 32 bits of (c) */  in jhash()
90 	case 12: c += (u32)k[11]<<24;  in jhash()
91 	case 11: c += (u32)k[10]<<16;  in jhash()
92 	case 10: c += (u32)k[9]<<8;  in jhash()
93 	case 9:  c += k[8];  in jhash()
98 	case 4:  a += (u32)k[3]<<24;  in jhash()
99 	case 3:  a += (u32)k[2]<<16;  in jhash()
100 	case 2:  a += (u32)k[1]<<8;  in jhash()
101 	case 1:  a += k[0];  in jhash()
102 		 __jhash_final(a, b, c);  in jhash()
107 	return c;  in jhash()
110 /* jhash2 - hash an array of u32's
119 	u32 a, b, c;  in jhash2()  local
122 	a = b = c = JHASH_INITVAL + (length<<2) + initval;  in jhash2()
126 		a += k[0];  in jhash2()
128 		c += k[2];  in jhash2()
129 		__jhash_mix(a, b, c);  in jhash2()
130 		length -= 3;  in jhash2()
136 	case 3: c += k[2];  in jhash2()
138 	case 1: a += k[0];  in jhash2()
139 		__jhash_final(a, b, c);  in jhash2()
144 	return c;  in jhash2()
148 /* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */
149 static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)  in __jhash_nwords()  argument
151 	a += initval;  in __jhash_nwords()
153 	c += initval;  in __jhash_nwords()
155 	__jhash_final(a, b, c);  in __jhash_nwords()
157 	return c;  in __jhash_nwords()
160 static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)  in jhash_3words()  argument
162 	return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2));  in jhash_3words()
165 static inline u32 jhash_2words(u32 a, u32 b, u32 initval)  in jhash_2words()  argument
167 	return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));  in jhash_2words()
170 static inline u32 jhash_1word(u32 a, u32 initval)  in jhash_1word()  argument
172 	return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2));  in jhash_1word()