1 2 #include <linux/ceph/types.h> 3 4 /* 5 * Robert Jenkin's hash function. 6 * http://burtleburtle.net/bob/hash/evahash.html 7 * This is in the public domain. 8 */ 9 #define mix(a, b, c) \ 10 do { \ 11 a = a - b; a = a - c; a = a ^ (c >> 13); \ 12 b = b - c; b = b - a; b = b ^ (a << 8); \ 13 c = c - a; c = c - b; c = c ^ (b >> 13); \ 14 a = a - b; a = a - c; a = a ^ (c >> 12); \ 15 b = b - c; b = b - a; b = b ^ (a << 16); \ 16 c = c - a; c = c - b; c = c ^ (b >> 5); \ 17 a = a - b; a = a - c; a = a ^ (c >> 3); \ 18 b = b - c; b = b - a; b = b ^ (a << 10); \ 19 c = c - a; c = c - b; c = c ^ (b >> 15); \ 20 } while (0) 21 22 unsigned ceph_str_hash_rjenkins(const char *str, unsigned length) 23 { 24 const unsigned char *k = (const unsigned char *)str; 25 __u32 a, b, c; /* the internal state */ 26 __u32 len; /* how many key bytes still need mixing */ 27 28 /* Set up the internal state */ 29 len = length; 30 a = 0x9e3779b9; /* the golden ratio; an arbitrary value */ 31 b = a; 32 c = 0; /* variable initialization of internal state */ 33 34 /* handle most of the key */ 35 while (len >= 12) { 36 a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) + 37 ((__u32)k[3] << 24)); 38 b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) + 39 ((__u32)k[7] << 24)); 40 c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) + 41 ((__u32)k[11] << 24)); 42 mix(a, b, c); 43 k = k + 12; 44 len = len - 12; 45 } 46 47 /* handle the last 11 bytes */ 48 c = c + length; 49 switch (len) { /* all the case statements fall through */ 50 case 11: 51 c = c + ((__u32)k[10] << 24); 52 case 10: 53 c = c + ((__u32)k[9] << 16); 54 case 9: 55 c = c + ((__u32)k[8] << 8); 56 /* the first byte of c is reserved for the length */ 57 case 8: 58 b = b + ((__u32)k[7] << 24); 59 case 7: 60 b = b + ((__u32)k[6] << 16); 61 case 6: 62 b = b + ((__u32)k[5] << 8); 63 case 5: 64 b = b + k[4]; 65 case 4: 66 a = a + ((__u32)k[3] << 24); 67 case 3: 68 a = a + ((__u32)k[2] << 16); 69 case 2: 70 a = a + ((__u32)k[1] << 8); 71 case 1: 72 a = a + k[0]; 73 /* case 0: nothing left to add */ 74 } 75 mix(a, b, c); 76 77 return c; 78 } 79 80 /* 81 * linux dcache hash 82 */ 83 unsigned ceph_str_hash_linux(const char *str, unsigned length) 84 { 85 unsigned long hash = 0; 86 unsigned char c; 87 88 while (length--) { 89 c = *str++; 90 hash = (hash + (c << 4) + (c >> 4)) * 11; 91 } 92 return hash; 93 } 94 95 96 unsigned ceph_str_hash(int type, const char *s, unsigned len) 97 { 98 switch (type) { 99 case CEPH_STR_HASH_LINUX: 100 return ceph_str_hash_linux(s, len); 101 case CEPH_STR_HASH_RJENKINS: 102 return ceph_str_hash_rjenkins(s, len); 103 default: 104 return -1; 105 } 106 } 107 108 const char *ceph_str_hash_name(int type) 109 { 110 switch (type) { 111 case CEPH_STR_HASH_LINUX: 112 return "linux"; 113 case CEPH_STR_HASH_RJENKINS: 114 return "rjenkins"; 115 default: 116 return "unknown"; 117 } 118 } 119