| 1 | #include <stdio.h> |
| 2 | |
| 3 | #include "lfsr.h" |
| 4 | |
| 5 | /* |
| 6 | * From table 3 of |
| 7 | * |
| 8 | * http://www.xilinx.com/support/documentation/application_notes/xapp052.pdf |
| 9 | */ |
| 10 | static struct lfsr_taps lfsr_taps[] = { |
| 11 | { |
| 12 | .length = 16, |
| 13 | .taps = { 16, 15, 13, 4, }, |
| 14 | }, |
| 15 | { |
| 16 | .length = 17, |
| 17 | .taps = { 17, 14, }, |
| 18 | }, |
| 19 | { |
| 20 | .length = 18, |
| 21 | .taps = { 18, 11, }, |
| 22 | }, |
| 23 | { |
| 24 | .length = 19, |
| 25 | .taps = { 19, 6, 2, 1, }, |
| 26 | }, |
| 27 | { |
| 28 | .length = 20, |
| 29 | .taps = { 20, 17, }, |
| 30 | }, |
| 31 | { |
| 32 | .length = 21, |
| 33 | .taps = { 21, 19, }, |
| 34 | }, |
| 35 | { |
| 36 | .length = 22, |
| 37 | .taps = { 22, 21, }, |
| 38 | }, |
| 39 | { |
| 40 | .length = 23, |
| 41 | .taps = { 23, 18, }, |
| 42 | }, |
| 43 | { |
| 44 | .length = 24, |
| 45 | .taps = { 24, 23, 22, 17, }, |
| 46 | }, |
| 47 | { |
| 48 | .length = 25, |
| 49 | .taps = { 25, 22, }, |
| 50 | }, |
| 51 | { |
| 52 | .length = 26, |
| 53 | .taps = {26, 6, 2, 1, }, |
| 54 | }, |
| 55 | { |
| 56 | .length = 27, |
| 57 | .taps = { 27, 5, 2, 1, }, |
| 58 | }, |
| 59 | { |
| 60 | .length = 28, |
| 61 | .taps = { 28, 25, }, |
| 62 | }, |
| 63 | { |
| 64 | .length = 29, |
| 65 | .taps = {29, 27, }, |
| 66 | }, |
| 67 | { |
| 68 | .length = 30, |
| 69 | .taps = { 30, 6, 4, 1, }, |
| 70 | }, |
| 71 | { |
| 72 | .length = 31, |
| 73 | .taps = { 31, 28, }, |
| 74 | }, |
| 75 | { |
| 76 | .length = 32, |
| 77 | .taps = { 32, 22, 2, 1, }, |
| 78 | }, |
| 79 | { |
| 80 | .length = 33, |
| 81 | .taps = { 33, 20, }, |
| 82 | }, |
| 83 | { |
| 84 | .length = 34, |
| 85 | .taps = { 34, 27, 2, 1, }, |
| 86 | }, |
| 87 | { |
| 88 | .length = 35, |
| 89 | .taps = { 35, 33, }, |
| 90 | }, |
| 91 | { |
| 92 | .length = 36, |
| 93 | .taps = { 36, 25, }, |
| 94 | }, |
| 95 | { |
| 96 | .length = 37, |
| 97 | .taps = { 37, 5, 4, 3, 2, 1, }, |
| 98 | }, |
| 99 | { |
| 100 | .length = 38, |
| 101 | .taps = { 38, 6, 5, 1, }, |
| 102 | }, |
| 103 | { |
| 104 | .length = 39, |
| 105 | .taps = { 39, 35, }, |
| 106 | }, |
| 107 | { |
| 108 | .length = 40, |
| 109 | .taps = { 40, 38, 21, 19, }, |
| 110 | }, |
| 111 | { |
| 112 | .length = 41, |
| 113 | .taps = { 41, 38, }, |
| 114 | }, |
| 115 | { |
| 116 | .length = 42, |
| 117 | .taps = { 42, 41, 20, 19, }, |
| 118 | }, |
| 119 | { |
| 120 | .length = 43, |
| 121 | .taps = { 43, 42, 38, 37, }, |
| 122 | }, |
| 123 | { |
| 124 | .length = 44, |
| 125 | .taps = { 44, 43, 38, 37, }, |
| 126 | }, |
| 127 | { |
| 128 | .length = 45, |
| 129 | .taps = { 45, 44, 42, 41, }, |
| 130 | }, |
| 131 | { |
| 132 | .length = 46, |
| 133 | .taps = { 46, 45, 26, 25, }, |
| 134 | }, |
| 135 | { |
| 136 | .length = 47, |
| 137 | .taps = { 47, 42, }, |
| 138 | }, |
| 139 | { |
| 140 | .length = 48, |
| 141 | .taps = { 48, 47, 21, 20, }, |
| 142 | }, |
| 143 | { |
| 144 | .length = 49, |
| 145 | .taps = { 49, 40, }, |
| 146 | }, |
| 147 | { |
| 148 | .length = 50, |
| 149 | .taps = { 50, 49, 36, 35, }, |
| 150 | }, |
| 151 | { |
| 152 | .length = 51, |
| 153 | .taps = { 51, 50, 36, 35, }, |
| 154 | }, |
| 155 | { |
| 156 | .length = 52, |
| 157 | .taps = { 52, 49, }, |
| 158 | }, |
| 159 | { |
| 160 | .length = 53, |
| 161 | .taps = { 53, 52, 38, 37 }, |
| 162 | }, |
| 163 | { |
| 164 | .length = 54, |
| 165 | .taps = { 54, 53, 18, 17 }, |
| 166 | }, |
| 167 | { |
| 168 | .length = 55, |
| 169 | .taps = { 55, 31, }, |
| 170 | }, |
| 171 | { |
| 172 | .length = 56, |
| 173 | .taps = { 56, 55, 35, 34, }, |
| 174 | }, |
| 175 | { |
| 176 | .length = 57, |
| 177 | .taps = { 57, 50, }, |
| 178 | }, |
| 179 | { |
| 180 | .length = 58, |
| 181 | .taps = { 58, 39, }, |
| 182 | }, |
| 183 | { |
| 184 | .length = 59, |
| 185 | .taps = { 59, 58, 38, 37, }, |
| 186 | }, |
| 187 | { |
| 188 | .length = 60, |
| 189 | .taps = { 60, 59, }, |
| 190 | }, |
| 191 | { |
| 192 | .length = 61, |
| 193 | .taps = { 61, 60, 46, 45, }, |
| 194 | }, |
| 195 | { |
| 196 | .length = 62, |
| 197 | .taps = { 62, 61, 6, 5, }, |
| 198 | }, |
| 199 | { |
| 200 | .length = 63, |
| 201 | .taps = { 63, 62, }, |
| 202 | }, |
| 203 | }; |
| 204 | |
| 205 | #define FIO_LFSR_CRANKS 128 |
| 206 | |
| 207 | static uint64_t __lfsr_next(uint64_t v, struct lfsr_taps *lt) |
| 208 | { |
| 209 | uint64_t xor_mask = 0; |
| 210 | int i; |
| 211 | |
| 212 | for (i = 0; lt->taps[i]; i++) |
| 213 | xor_mask ^= (v << (lt->taps[i] - 1)); |
| 214 | |
| 215 | xor_mask &= ~(~0UL << 1) << (lt->length - 1); |
| 216 | return xor_mask | (v >> 1); |
| 217 | } |
| 218 | |
| 219 | int lfsr_next(struct fio_lfsr *fl, uint64_t *off, uint64_t last) |
| 220 | { |
| 221 | if (fl->num_vals > fl->max_val) |
| 222 | return 1; |
| 223 | |
| 224 | do { |
| 225 | fl->last_val = __lfsr_next(fl->last_val, &fl->taps); |
| 226 | if (fl->last_val - 1 <= fl->max_val && |
| 227 | fl->last_val <= last) |
| 228 | break; |
| 229 | } while (1); |
| 230 | |
| 231 | *off = fl->last_val - 1; |
| 232 | fl->num_vals++; |
| 233 | return 0; |
| 234 | } |
| 235 | |
| 236 | static struct lfsr_taps *find_lfsr(uint64_t size) |
| 237 | { |
| 238 | int i; |
| 239 | |
| 240 | for (i = 0; lfsr_taps[i].length; i++) |
| 241 | if (((1UL << lfsr_taps[i].length) + FIO_LFSR_CRANKS) >= size) |
| 242 | return &lfsr_taps[i]; |
| 243 | |
| 244 | return NULL; |
| 245 | } |
| 246 | |
| 247 | int lfsr_init(struct fio_lfsr *fl, uint64_t size, unsigned long seed) |
| 248 | { |
| 249 | struct lfsr_taps *tap; |
| 250 | int i; |
| 251 | |
| 252 | tap = find_lfsr(size); |
| 253 | if (!tap) |
| 254 | return 1; |
| 255 | |
| 256 | fl->last_val = seed; |
| 257 | fl->max_val = size - 1; |
| 258 | fl->num_vals = 0; |
| 259 | fl->taps.length = tap->length; |
| 260 | for (i = 0; i < FIO_MAX_TAPS; i++) { |
| 261 | fl->taps.taps[i] = tap->taps[i]; |
| 262 | if (!fl->taps.taps[i]) |
| 263 | break; |
| 264 | } |
| 265 | |
| 266 | for (i = 0; i < FIO_LFSR_CRANKS; i++) |
| 267 | fl->last_val = __lfsr_next(fl->last_val, &fl->taps); |
| 268 | |
| 269 | return 0; |
| 270 | } |