1 /* $OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert Exp $ */ 2 /*- 3 * Copyright (c) 1992, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Peter McIlroy. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Hybrid exponential search/linear search merge sort with hybrid 36 * natural/pairwise first pass. Requires about .3% more comparisons 37 * for random data than LSMS with pairwise first pass alone. 38 * It works for objects as small as two bytes. 39 */ 40 41 #define NATURAL 42 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ 43 44 /* #define NATURAL to get hybrid natural merge. 45 * (The default is pairwise merging.) 46 */ 47 48 #include <sys/types.h> 49 50 #include <errno.h> 51 #include <stdlib.h> 52 #include <string.h> 53 54 static void setup(u_char *list1, u_char *list2, size_t n, size_t size, 55 int (*cmp)(const void *, const void *)); 56 static void insertionsort(u_char *a, size_t n, size_t size, 57 int (*cmp)(const void *, const void *)); 58 59 #define ISIZE sizeof(int) 60 #define PSIZE sizeof(u_char *) 61 #define ICOPY_LIST(src, dst, last) \ 62 do \ 63 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ 64 while(src < last) 65 #define ICOPY_ELT(src, dst, i) \ 66 do \ 67 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ 68 while (i -= ISIZE) 69 70 #define CCOPY_LIST(src, dst, last) \ 71 do \ 72 *dst++ = *src++; \ 73 while (src < last) 74 #define CCOPY_ELT(src, dst, i) \ 75 do \ 76 *dst++ = *src++; \ 77 while (i -= 1) 78 79 /* 80 * Find the next possible pointer head. (Trickery for forcing an array 81 * to do double duty as a linked list when objects do not align with word 82 * boundaries. 83 */ 84 /* Assumption: PSIZE is a power of 2. */ 85 #define EVAL(p) (u_char **) \ 86 ((u_char *)0 + \ 87 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))) 88 89 /* 90 * Arguments are as for qsort. 91 */ 92 int 93 mergesort(void *base, size_t nmemb, size_t size, 94 int (*cmp)(const void *, const void *)) 95 { 96 int i, sense; 97 int big, iflag; 98 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 99 u_char *list2, *list1, *p2, *p, *last, **p1; 100 101 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 102 errno = EINVAL; 103 return (-1); 104 } 105 106 if (nmemb == 0) 107 return (0); 108 109 /* 110 * XXX 111 * Stupid subtraction for the Cray. 112 */ 113 iflag = 0; 114 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 115 iflag = 1; 116 117 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 118 return (-1); 119 120 list1 = base; 121 setup(list1, list2, nmemb, size, cmp); 122 last = list2 + nmemb * size; 123 i = big = 0; 124 while (*EVAL(list2) != last) { 125 l2 = list1; 126 p1 = EVAL(list1); 127 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 128 p2 = *EVAL(p2); 129 f1 = l2; 130 f2 = l1 = list1 + (p2 - list2); 131 if (p2 != last) 132 p2 = *EVAL(p2); 133 l2 = list1 + (p2 - list2); 134 while (f1 < l1 && f2 < l2) { 135 if ((*cmp)(f1, f2) <= 0) { 136 q = f2; 137 b = f1, t = l1; 138 sense = -1; 139 } else { 140 q = f1; 141 b = f2, t = l2; 142 sense = 0; 143 } 144 if (!big) { /* here i = 0 */ 145 while ((b += size) < t && cmp(q, b) >sense) 146 if (++i == 6) { 147 big = 1; 148 goto EXPONENTIAL; 149 } 150 } else { 151 EXPONENTIAL: for (i = size; ; i <<= 1) 152 if ((p = (b + i)) >= t) { 153 if ((p = t - size) > b && 154 (*cmp)(q, p) <= sense) 155 t = p; 156 else 157 b = p; 158 break; 159 } else if ((*cmp)(q, p) <= sense) { 160 t = p; 161 if (i == size) 162 big = 0; 163 goto FASTCASE; 164 } else 165 b = p; 166 while (t > b+size) { 167 i = (((t - b) / size) >> 1) * size; 168 if ((*cmp)(q, p = b + i) <= sense) 169 t = p; 170 else 171 b = p; 172 } 173 goto COPY; 174 FASTCASE: while (i > size) 175 if ((*cmp)(q, 176 p = b + (i >>= 1)) <= sense) 177 t = p; 178 else 179 b = p; 180 COPY: b = t; 181 } 182 i = size; 183 if (q == f1) { 184 if (iflag) { 185 ICOPY_LIST(f2, tp2, b); 186 ICOPY_ELT(f1, tp2, i); 187 } else { 188 CCOPY_LIST(f2, tp2, b); 189 CCOPY_ELT(f1, tp2, i); 190 } 191 } else { 192 if (iflag) { 193 ICOPY_LIST(f1, tp2, b); 194 ICOPY_ELT(f2, tp2, i); 195 } else { 196 CCOPY_LIST(f1, tp2, b); 197 CCOPY_ELT(f2, tp2, i); 198 } 199 } 200 } 201 if (f2 < l2) { 202 if (iflag) 203 ICOPY_LIST(f2, tp2, l2); 204 else 205 CCOPY_LIST(f2, tp2, l2); 206 } else if (f1 < l1) { 207 if (iflag) 208 ICOPY_LIST(f1, tp2, l1); 209 else 210 CCOPY_LIST(f1, tp2, l1); 211 } 212 *p1 = l2; 213 } 214 tp2 = list1; /* swap list1, list2 */ 215 list1 = list2; 216 list2 = tp2; 217 last = list2 + nmemb*size; 218 } 219 if (base == list2) { 220 memmove(list2, list1, nmemb*size); 221 list2 = list1; 222 } 223 free(list2); 224 return (0); 225 } 226 227 #define swap(a, b) { \ 228 s = b; \ 229 i = size; \ 230 do { \ 231 tmp = *a; *a++ = *s; *s++ = tmp; \ 232 } while (--i); \ 233 a -= size; \ 234 } 235 #define reverse(bot, top) { \ 236 s = top; \ 237 do { \ 238 i = size; \ 239 do { \ 240 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 241 } while (--i); \ 242 s -= size2; \ 243 } while(bot < s); \ 244 } 245 246 /* 247 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 248 * increasing order, list2 in a corresponding linked list. Checks for runs 249 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 250 * is defined. Otherwise simple pairwise merging is used.) 251 */ 252 void 253 setup(u_char *list1, u_char *list2, size_t n, size_t size, 254 int (*cmp)(const void *, const void *)) 255 { 256 int i, length, size2, sense; 257 u_char tmp, *f1, *f2, *s, *l2, *last, *p2; 258 259 size2 = size*2; 260 if (n <= 5) { 261 insertionsort(list1, n, size, cmp); 262 *EVAL(list2) = (u_char*) list2 + n*size; 263 return; 264 } 265 /* 266 * Avoid running pointers out of bounds; limit n to evens 267 * for simplicity. 268 */ 269 i = 4 + (n & 1); 270 insertionsort(list1 + (n - i) * size, i, size, cmp); 271 last = list1 + size * (n - i); 272 *EVAL(list2 + (last - list1)) = list2 + n * size; 273 274 #ifdef NATURAL 275 p2 = list2; 276 f1 = list1; 277 sense = (cmp(f1, f1 + size) > 0); 278 for (; f1 < last; sense = !sense) { 279 length = 2; 280 /* Find pairs with same sense. */ 281 for (f2 = f1 + size2; f2 < last; f2 += size2) { 282 if ((cmp(f2, f2+ size) > 0) != sense) 283 break; 284 length += 2; 285 } 286 if (length < THRESHOLD) { /* Pairwise merge */ 287 do { 288 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 289 if (sense > 0) 290 swap (f1, f1 + size); 291 } while ((f1 += size2) < f2); 292 } else { /* Natural merge */ 293 l2 = f2; 294 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 295 if ((cmp(f2-size, f2) > 0) != sense) { 296 p2 = *EVAL(p2) = f2 - list1 + list2; 297 if (sense > 0) 298 reverse(f1, f2-size); 299 f1 = f2; 300 } 301 } 302 if (sense > 0) 303 reverse (f1, f2-size); 304 f1 = f2; 305 if (f2 < last || cmp(f2 - size, f2) > 0) 306 p2 = *EVAL(p2) = f2 - list1 + list2; 307 else 308 p2 = *EVAL(p2) = list2 + n*size; 309 } 310 } 311 #else /* pairwise merge only. */ 312 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 313 p2 = *EVAL(p2) = p2 + size2; 314 if (cmp (f1, f1 + size) > 0) 315 swap(f1, f1 + size); 316 } 317 #endif /* NATURAL */ 318 } 319 320 /* 321 * This is to avoid out-of-bounds addresses in sorting the 322 * last 4 elements. 323 */ 324 static void 325 insertionsort(u_char *a, size_t n, size_t size, 326 int (*cmp)(const void *, const void *)) 327 { 328 u_char *ai, *s, *t, *u, tmp; 329 int i; 330 331 for (ai = a+size; --n >= 1; ai += size) 332 for (t = ai; t > a; t -= size) { 333 u = t - size; 334 if (cmp(u, t) <= 0) 335 break; 336 swap(u, t); 337 } 338 } 339