1 /* Modified for use with yasm by Peter Johnson. */ 2 #include "util.h" 3 4 /* 5 -------------------------------------------------------------------- 6 lookupa.c, by Bob Jenkins, December 1996. Same as lookup2.c 7 Use this code however you wish. Public Domain. No warranty. 8 Source is http://burtleburtle.net/bob/c/lookupa.c 9 -------------------------------------------------------------------- 10 */ 11 #include "phash.h" 12 13 #define ub4 unsigned long 14 15 #define hashsize(n) ((ub4)1<<(n)) 16 #define hashmask(n) (hashsize(n)-1) 17 18 /* 19 -------------------------------------------------------------------- 20 mix -- mix 3 32-bit values reversibly. 21 For every delta with one or two bit set, and the deltas of all three 22 high bits or all three low bits, whether the original value of a,b,c 23 is almost all zero or is uniformly distributed, 24 * If mix() is run forward or backward, at least 32 bits in a,b,c 25 have at least 1/4 probability of changing. 26 * If mix() is run forward, every bit of c will change between 1/3 and 27 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.) 28 mix() was built out of 36 single-cycle latency instructions in a 29 structure that could supported 2x parallelism, like so: 30 a -= b; 31 a -= c; x = (c>>13); 32 b -= c; a ^= x; 33 b -= a; x = (a<<8); 34 c -= a; b ^= x; 35 c -= b; x = (b>>13); 36 ... 37 Unfortunately, superscalar Pentiums and Sparcs can't take advantage 38 of that parallelism. They've also turned some of those single-cycle 39 latency instructions into multi-cycle latency instructions. Still, 40 this is the fastest good hash I could find. There were about 2^^68 41 to choose from. I only looked at a billion or so. 42 -------------------------------------------------------------------- 43 */ 44 #define mix(a,b,c) \ 45 { \ 46 a -= b; a -= c; a ^= (c>>13); \ 47 a &= 0xffffffff; \ 48 b -= c; b -= a; b ^= (a<<8); \ 49 b &= 0xffffffff; \ 50 c -= a; c -= b; c ^= (b>>13); \ 51 c &= 0xffffffff; \ 52 a -= b; a -= c; a ^= (c>>12); \ 53 a &= 0xffffffff; \ 54 b -= c; b -= a; b ^= (a<<16); \ 55 b &= 0xffffffff; \ 56 c -= a; c -= b; c ^= (b>>5); \ 57 c &= 0xffffffff; \ 58 a -= b; a -= c; a ^= (c>>3); \ 59 a &= 0xffffffff; \ 60 b -= c; b -= a; b ^= (a<<10); \ 61 b &= 0xffffffff; \ 62 c -= a; c -= b; c ^= (b>>15); \ 63 c &= 0xffffffff; \ 64 } 65 66 /* 67 -------------------------------------------------------------------- 68 lookup() -- hash a variable-length key into a 32-bit value 69 k : the key (the unaligned variable-length array of bytes) 70 len : the length of the key, counting by bytes 71 level : can be any 4-byte value 72 Returns a 32-bit value. Every bit of the key affects every bit of 73 the return value. Every 1-bit and 2-bit delta achieves avalanche. 74 About 6len+35 instructions. 75 76 The best hash table sizes are powers of 2. There is no need to do 77 mod a prime (mod is sooo slow!). If you need less than 32 bits, 78 use a bitmask. For example, if you need only 10 bits, do 79 h = (h & hashmask(10)); 80 In which case, the hash table should have hashsize(10) elements. 81 82 If you are hashing n strings (ub1 **)k, do it like this: 83 for (i=0, h=0; i<n; ++i) h = lookup( k[i], len[i], h); 84 85 By Bob Jenkins, 1996. bob_jenkins (at) burtleburtle.net. You may use this 86 code any way you wish, private, educational, or commercial. 87 88 See http://burtleburtle.net/bob/hash/evahash.html 89 Use for hash table lookup, or anything where one collision in 2^32 is 90 acceptable. Do NOT use for cryptographic purposes. 91 -------------------------------------------------------------------- 92 */ 93 94 unsigned long 95 phash_lookup( 96 register const char *sk, /* the key */ 97 register size_t length, /* the length of the key */ 98 register unsigned long level) /* the previous hash, or an arbitrary value */ 99 { 100 register unsigned long a,b,c; 101 register size_t len; 102 register const unsigned char *k = (const unsigned char *)sk; 103 104 /* Set up the internal state */ 105 len = length; 106 a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */ 107 c = level; /* the previous hash value */ 108 109 /*---------------------------------------- handle most of the key */ 110 while (len >= 12) 111 { 112 a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24)); 113 a &= 0xffffffff; 114 b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24)); 115 b &= 0xffffffff; 116 c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24)); 117 c &= 0xffffffff; 118 mix(a,b,c); 119 k += 12; len -= 12; 120 } 121 122 /*------------------------------------- handle the last 11 bytes */ 123 c += (ub4)length; 124 switch(len) /* all the case statements fall through */ 125 { 126 case 11: c+=((ub4)k[10]<<24); 127 case 10: c+=((ub4)k[9]<<16); 128 case 9 : c+=((ub4)k[8]<<8); 129 c &= 0xffffffff; 130 /* the first byte of c is reserved for the length */ 131 case 8 : b+=((ub4)k[7]<<24); 132 case 7 : b+=((ub4)k[6]<<16); 133 case 6 : b+=((ub4)k[5]<<8); 134 case 5 : b+=k[4]; 135 b &= 0xffffffff; 136 case 4 : a+=((ub4)k[3]<<24); 137 case 3 : a+=((ub4)k[2]<<16); 138 case 2 : a+=((ub4)k[1]<<8); 139 case 1 : a+=k[0]; 140 a &= 0xffffffff; 141 /* case 0: nothing left to add */ 142 } 143 mix(a,b,c); 144 /*-------------------------------------------- report the result */ 145 return c; 146 } 147 148 149 /* 150 -------------------------------------------------------------------- 151 mixc -- mixc 8 4-bit values as quickly and thoroughly as possible. 152 Repeating mix() three times achieves avalanche. 153 Repeating mix() four times eliminates all funnels and all 154 characteristics stronger than 2^{-11}. 155 -------------------------------------------------------------------- 156 */ 157 #define mixc(a,b,c,d,e,f,g,h) \ 158 { \ 159 a^=b<<11; d+=a; b+=c; \ 160 b^=c>>2; e+=b; c+=d; \ 161 c^=d<<8; f+=c; d+=e; \ 162 d^=e>>16; g+=d; e+=f; \ 163 e^=f<<10; h+=e; f+=g; \ 164 f^=g>>4; a+=f; g+=h; \ 165 g^=h<<8; b+=g; h+=a; \ 166 h^=a>>9; c+=h; a+=b; \ 167 } 168 169 /* 170 -------------------------------------------------------------------- 171 checksum() -- hash a variable-length key into a 256-bit value 172 k : the key (the unaligned variable-length array of bytes) 173 len : the length of the key, counting by bytes 174 state : an array of CHECKSTATE 4-byte values (256 bits) 175 The state is the checksum. Every bit of the key affects every bit of 176 the state. There are no funnels. About 112+6.875len instructions. 177 178 If you are hashing n strings (ub1 **)k, do it like this: 179 for (i=0; i<8; ++i) state[i] = 0x9e3779b9; 180 for (i=0, h=0; i<n; ++i) checksum( k[i], len[i], state); 181 182 (c) Bob Jenkins, 1996. bob_jenkins (at) burtleburtle.net. You may use this 183 code any way you wish, private, educational, or commercial, as long 184 as this whole comment accompanies it. 185 186 See http://burtleburtle.net/bob/hash/evahash.html 187 Use to detect changes between revisions of documents, assuming nobody 188 is trying to cause collisions. Do NOT use for cryptography. 189 -------------------------------------------------------------------- 190 */ 191 void 192 phash_checksum( 193 register const char *sk, 194 register size_t len, 195 register unsigned long *state) 196 { 197 register unsigned long a,b,c,d,e,f,g,h; 198 register size_t length; 199 register const unsigned char *k = (const unsigned char *)sk; 200 201 /* Use the length and level; add in the golden ratio. */ 202 length = len; 203 a=state[0]; b=state[1]; c=state[2]; d=state[3]; 204 e=state[4]; f=state[5]; g=state[6]; h=state[7]; 205 206 /*---------------------------------------- handle most of the key */ 207 while (len >= 32) 208 { 209 a += (k[0] +(k[1]<<8) +(k[2]<<16) +(k[3]<<24)); 210 b += (k[4] +(k[5]<<8) +(k[6]<<16) +(k[7]<<24)); 211 c += (k[8] +(k[9]<<8) +(k[10]<<16)+(k[11]<<24)); 212 d += (k[12]+(k[13]<<8)+(k[14]<<16)+(k[15]<<24)); 213 e += (k[16]+(k[17]<<8)+(k[18]<<16)+(k[19]<<24)); 214 f += (k[20]+(k[21]<<8)+(k[22]<<16)+(k[23]<<24)); 215 g += (k[24]+(k[25]<<8)+(k[26]<<16)+(k[27]<<24)); 216 h += (k[28]+(k[29]<<8)+(k[30]<<16)+(k[31]<<24)); 217 mixc(a,b,c,d,e,f,g,h); 218 mixc(a,b,c,d,e,f,g,h); 219 mixc(a,b,c,d,e,f,g,h); 220 mixc(a,b,c,d,e,f,g,h); 221 k += 32; len -= 32; 222 } 223 224 /*------------------------------------- handle the last 31 bytes */ 225 h += (ub4)length; 226 switch(len) 227 { 228 case 31: h+=(k[30]<<24); 229 case 30: h+=(k[29]<<16); 230 case 29: h+=(k[28]<<8); 231 case 28: g+=(k[27]<<24); 232 case 27: g+=(k[26]<<16); 233 case 26: g+=(k[25]<<8); 234 case 25: g+=k[24]; 235 case 24: f+=(k[23]<<24); 236 case 23: f+=(k[22]<<16); 237 case 22: f+=(k[21]<<8); 238 case 21: f+=k[20]; 239 case 20: e+=(k[19]<<24); 240 case 19: e+=(k[18]<<16); 241 case 18: e+=(k[17]<<8); 242 case 17: e+=k[16]; 243 case 16: d+=(k[15]<<24); 244 case 15: d+=(k[14]<<16); 245 case 14: d+=(k[13]<<8); 246 case 13: d+=k[12]; 247 case 12: c+=(k[11]<<24); 248 case 11: c+=(k[10]<<16); 249 case 10: c+=(k[9]<<8); 250 case 9 : c+=k[8]; 251 case 8 : b+=(k[7]<<24); 252 case 7 : b+=(k[6]<<16); 253 case 6 : b+=(k[5]<<8); 254 case 5 : b+=k[4]; 255 case 4 : a+=(k[3]<<24); 256 case 3 : a+=(k[2]<<16); 257 case 2 : a+=(k[1]<<8); 258 case 1 : a+=k[0]; 259 } 260 mixc(a,b,c,d,e,f,g,h); 261 mixc(a,b,c,d,e,f,g,h); 262 mixc(a,b,c,d,e,f,g,h); 263 mixc(a,b,c,d,e,f,g,h); 264 265 /*-------------------------------------------- report the result */ 266 state[0]=a; state[1]=b; state[2]=c; state[3]=d; 267 state[4]=e; state[5]=f; state[6]=g; state[7]=h; 268 } 269
