chunker.c (6135B)
1 #include <stdint.h> 2 #include <stdio.h> 3 #include <stdlib.h> 4 #include <string.h> 5 #include <unistd.h> 6 7 #include "misc.h" 8 9 #define ROTL(x, y) (((x) << (y)) | ((x) >> (32 - (y)))) 10 11 struct chunker { 12 unsigned char *buf; 13 int fd; 14 size_t rp; 15 size_t wp; 16 size_t minsize; 17 size_t maxsize; 18 size_t mask; 19 size_t winsize; 20 uint32_t seed; 21 }; 22 23 /* 24 * Static table for use in buzhash algorithm. 25 * 256 * 32 bits randomly generated unique integers 26 * 27 * To get better pseudo-random results, there is exactly the same number 28 * of 0 and 1 spread amongst these integers. It means that there is 29 * exactly 50% chance that a XOR operation would flip all the bits in 30 * the hash. 31 */ 32 static uint32_t buztbl[] = { 33 0xbc9fa594,0x30a8f827,0xced627a7,0xdb46a745,0xcfa4a9e8,0x77cccb59,0xddb66276,0x3adc532f, 34 0xfe8b67d3,0x8155b59e,0x0c893666,0x1d757009,0x17394ee4,0x85d94c07,0xcacd52da,0x076c6f79, 35 0xead0a798,0x6c7ccb4a,0x2639a1b8,0x3aa5ae32,0x3e6218d2,0xb290d980,0xa5149521,0x4b426119, 36 0xd3230fc7,0x677c1cc4,0x2b64603c,0x01fe92a8,0xbe358296,0xa7e7fac7,0xf509bf41,0x04b017ad, 37 0xf900344c,0x8e14e202,0xb2a6e9b4,0x3db3c311,0x960286a8,0xf6bf0468,0xed54ec94,0xf358070c, 38 0x6a4795dd,0x3f7b925c,0x5e13a060,0xfaecbafe,0x03c8bb55,0x8a56ba88,0x633e3b49,0xe036bbbe, 39 0x1ed3dbb5,0x76e8ad74,0x79d346ab,0x44b4ccc4,0x71eb22d3,0xa1aa3f24,0x50e05b81,0xa3b450d3, 40 0x7f5caffb,0xa1990650,0x54c44800,0xda134b65,0x72362eea,0xbd12b8e6,0xf7c99fdc,0x020d48c7, 41 0x9d9c3d46,0x32b75615,0xe61923cf,0xadc09d8f,0xab11376b,0xd66fe4cd,0xb3b086b6,0xb8345b9f, 42 0x59029667,0xae0e937c,0xcbd4d4ba,0x720bb3fb,0x5f7d2ca3,0xec24ba15,0x6b40109b,0xf0a54587, 43 0x3acf9420,0x466e981d,0xc66dc124,0x150ef7b4,0xc3ce718e,0x136774f5,0x46684ab4,0xb4b490f0, 44 0x26508a8b,0xf12febc8,0x4b99171b,0xfc373c84,0x339b5677,0x41703ff3,0x7cadbbd7,0x15ea24e2, 45 0x7a2f9783,0xed6a383a,0x649eb072,0x79970941,0x2abd28ad,0x4375e00c,0x9df084f7,0x6fdeec6c, 46 0x6619ac6d,0x7d256f4d,0x9b8e658a,0x3d7627e9,0xd5a98d45,0x15f84223,0x9b6acef5,0xf876be67, 47 0xe3ae7089,0x84e2b64a,0x6818a969,0x86e9ba4e,0xa24a5b57,0x61570cf1,0xa5f8fc91,0x879d8383, 48 0x91b13866,0x75e87961,0x16db8138,0x5a2ff6b8,0x8f664e9b,0x894e1496,0x88235c5b,0xcdb3b580, 49 0xa2e80109,0xb0f88a82,0xd12cd340,0x93fbc37d,0xf4d1eb82,0xce42f309,0x16ffd2c2,0xb4dfef2b, 50 0xb8b1a33e,0x4708a5e6,0xba66dd88,0xa9ec0da6,0x6f8ee2c9,0xad8b9993,0x1d6a25a8,0x1f3d08ce, 51 0x149c04e7,0x5cd1fa51,0xb84c89c7,0xeced6f8c,0xe328b30f,0x084fa836,0x6d1bb1b7,0x94c78ea5, 52 0x14973034,0xf1a1bcef,0x48b798d2,0xded9ca9e,0x5fd965d0,0x92544eb1,0x5e80f189,0xcbbf5e15, 53 0x4d8121f0,0x5dd3b92f,0xd9ea98fb,0x2dbf5644,0x0fbcb9b7,0x20a1db53,0x7c3fcc98,0x36744fbd, 54 0xced08954,0x8e7c5efe,0x3c5f6733,0x657477be,0x3630a02d,0x38bcbda0,0xb7702575,0x4a7f4bce, 55 0x0e7660fe,0x4dcb91b5,0x4fd7ffd3,0x041821c1,0xa846a181,0xc8048e9e,0xd4b05072,0x986e0509, 56 0xa00aaeeb,0x02e3526a,0x2fac4843,0xfa98e805,0x923ecd8d,0x395d9546,0x8674c3cd,0xae5a8a71, 57 0x966dfe45,0x5c9ceba5,0x0830a1cf,0xa1750981,0x8f604480,0x28ea0c9a,0x0da12413,0x98b0b3c5, 58 0xa21d473a,0x96ce4308,0xe9a1001b,0x8bbacb44,0x18bad3f4,0xe3121acb,0x46a9b45f,0x92cd9704, 59 0xc1a7c619,0x3281e361,0x462e8c79,0x9e572f93,0x7239e5f0,0x67d8e6ba,0x13747ce3,0xf01ee64a, 60 0xe7d0ae12,0xeea04088,0xe5b36767,0x17558eae,0x678ffbe6,0xe0bbc866,0x0c24adec,0xa9cbb869, 61 0x3fd44ee1,0x9ca4ca06,0x04c0ef00,0x04589a21,0x9cf9c819,0x976f6ca1,0x8a30e66a,0x004d6f7e, 62 0x384c8851,0x5bc97eb8,0xc6c49339,0x5aa386c7,0x74bdf8af,0x9b713750,0x4112f8c2,0x2895dae1, 63 0xf576d905,0x9de98bce,0xb2b26bcd,0xd46707a0,0x147fbb46,0xa52c6e50,0xe43128fc,0x374ad964, 64 0x8dfd4d53,0xc4d0c087,0x31dfb5ca,0xa44589b5,0x6b637e2e,0x663f6b45,0xd2d8baa0,0x1dac7e4c 65 }; 66 67 /* Buzhash: https://en.wikipedia.org/wiki/Rolling_hash#Cyclic_polynomial */ 68 static inline uint32_t 69 hinit(unsigned char *buf, size_t size) 70 { 71 uint32_t sum; 72 size_t i; 73 74 for (i = 1, sum = 0; i < size; i++, buf++) 75 sum ^= ROTL(buztbl[*buf], (size - i) % 32); 76 return sum ^ buztbl[*buf]; 77 } 78 79 static inline uint32_t 80 hupdate(uint32_t sum, unsigned char out, unsigned char in, size_t size) 81 { 82 return ROTL(sum, 1) ^ ROTL(buztbl[out], size % 32) ^ buztbl[in]; 83 } 84 85 static size_t 86 cgetsize(struct chunker *c) 87 { 88 size_t maxcsize, winsize, i; 89 uint32_t sum; 90 unsigned char *bp; 91 92 maxcsize = c->wp - c->rp; 93 winsize = c->winsize; 94 if (maxcsize < winsize) 95 return maxcsize; 96 97 /* 98 * To achieve better deduplication, we chunk blocks based on a 99 * recurring pattern on the data stream. We slide a fixed window 100 * of WINSIZE bytes over the data, and a rolling hash is computed 101 * for this window. 102 * When the rolling hash matches a given pattern the block is chunked 103 * at the end of that window. 104 */ 105 bp = &c->buf[c->rp]; 106 sum = hinit(bp, winsize); 107 for (i = 0; i < maxcsize - winsize; i++) { 108 size_t csize = i + winsize; 109 110 if (i > 0) { 111 unsigned char out = bp[i - 1]; 112 unsigned char in = bp[csize - 1]; 113 114 sum = hupdate(sum, out, in, winsize); 115 } 116 117 if (csize < c->minsize) 118 continue; 119 120 if ((sum & c->mask) == 0) 121 return csize; 122 } 123 return maxcsize; 124 } 125 126 struct chunker * 127 copen(int fd, size_t minsize, size_t maxsize, 128 size_t mask, size_t winsize, uint32_t seed) 129 { 130 struct chunker *c; 131 size_t i; 132 133 c = calloc(1, sizeof(*c)); 134 if (c == NULL) { 135 seterr("calloc: out of memory"); 136 return NULL; 137 } 138 139 c->buf = calloc(1, maxsize); 140 if (c->buf == NULL) { 141 free(c); 142 seterr("calloc: out of memory"); 143 return NULL; 144 } 145 146 c->fd = fd; 147 c->minsize = minsize; 148 c->maxsize = maxsize; 149 c->mask = mask; 150 c->winsize = winsize; 151 c->seed = seed; 152 153 for (i = 0; i < sizeof(buztbl) / sizeof(buztbl[0]); i++) 154 buztbl[i] ^= c->seed; 155 return c; 156 } 157 158 void 159 cclose(struct chunker *c) 160 { 161 free(c->buf); 162 free(c); 163 } 164 165 ssize_t 166 cfill(struct chunker *c) 167 { 168 unsigned char *bp; 169 ssize_t n; 170 171 bp = &c->buf[c->wp]; 172 n = xread(c->fd, bp, c->maxsize - c->wp); 173 c->wp += n; 174 return c->wp; 175 } 176 177 void * 178 cget(struct chunker *c, size_t *csize) 179 { 180 unsigned char *bp; 181 182 if (c->rp == c->wp) { 183 seterr("chunker underflow"); 184 return NULL; 185 } 186 187 bp = &c->buf[c->rp]; 188 *csize = cgetsize(c); 189 c->rp += *csize; 190 return bp; 191 } 192 193 size_t 194 cdrain(struct chunker *c) 195 { 196 unsigned char *src, *dst; 197 198 src = &c->buf[c->rp]; 199 dst = c->buf; 200 memmove(dst, src, c->wp - c->rp); 201 c->wp -= c->rp; 202 c->rp = 0; 203 return c->wp; 204 }