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 *, u_char *, size_t, size_t, int (*)()); 55 static void insertionsort(u_char *, size_t, size_t, int (*)()); 56 57 #define ISIZE sizeof(int) 58 #define PSIZE sizeof(u_char *) 59 #define ICOPY_LIST(src, dst, last) \ 60 do \ 61 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ 62 while(src < last) 63 #define ICOPY_ELT(src, dst, i) \ 64 do \ 65 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ 66 while (i -= ISIZE) 67 68 #define CCOPY_LIST(src, dst, last) \ 69 do \ 70 *dst++ = *src++; \ 71 while (src < last) 72 #define CCOPY_ELT(src, dst, i) \ 73 do \ 74 *dst++ = *src++; \ 75 while (i -= 1) 76 77 /* 78 * Find the next possible pointer head. (Trickery for forcing an array 79 * to do double duty as a linked list when objects do not align with word 80 * boundaries. 81 */ 82 /* Assumption: PSIZE is a power of 2. */ 83 #define EVAL(p) (u_char **) \ 84 ((u_char *)0 + \ 85 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))) 86 87 /* 88 * Arguments are as for qsort. 89 */ 90 int 91 mergesort(void *base, size_t nmemb, size_t size, 92 int (*cmp)(const void *, const void *)) 93 { 94 int i, sense; 95 int big, iflag; 96 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 97 u_char *list2, *list1, *p2, *p, *last, **p1; 98 99 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 100 errno = EINVAL; 101 return (-1); 102 } 103 104 if (nmemb == 0) 105 return (0); 106 107 /* 108 * XXX 109 * Stupid subtraction for the Cray. 110 */ 111 iflag = 0; 112 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 113 iflag = 1; 114 115 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 116 return (-1); 117 118 list1 = base; 119 setup(list1, list2, nmemb, size, cmp); 120 last = list2 + nmemb * size; 121 i = big = 0; 122 while (*EVAL(list2) != last) { 123 l2 = list1; 124 p1 = EVAL(list1); 125 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 126 p2 = *EVAL(p2); 127 f1 = l2; 128 f2 = l1 = list1 + (p2 - list2); 129 if (p2 != last) 130 p2 = *EVAL(p2); 131 l2 = list1 + (p2 - list2); 132 while (f1 < l1 && f2 < l2) { 133 if ((*cmp)(f1, f2) <= 0) { 134 q = f2; 135 b = f1, t = l1; 136 sense = -1; 137 } else { 138 q = f1; 139 b = f2, t = l2; 140 sense = 0; 141 } 142 if (!big) { /* here i = 0 */ 143 while ((b += size) < t && cmp(q, b) >sense) 144 if (++i == 6) { 145 big = 1; 146 goto EXPONENTIAL; 147 } 148 } else { 149 EXPONENTIAL: for (i = size; ; i <<= 1) 150 if ((p = (b + i)) >= t) { 151 if ((p = t - size) > b && 152 (*cmp)(q, p) <= sense) 153 t = p; 154 else 155 b = p; 156 break; 157 } else if ((*cmp)(q, p) <= sense) { 158 t = p; 159 if (i == size) 160 big = 0; 161 goto FASTCASE; 162 } else 163 b = p; 164 while (t > b+size) { 165 i = (((t - b) / size) >> 1) * size; 166 if ((*cmp)(q, p = b + i) <= sense) 167 t = p; 168 else 169 b = p; 170 } 171 goto COPY; 172 FASTCASE: while (i > size) 173 if ((*cmp)(q, 174 p = b + (i >>= 1)) <= sense) 175 t = p; 176 else 177 b = p; 178 COPY: b = t; 179 } 180 i = size; 181 if (q == f1) { 182 if (iflag) { 183 ICOPY_LIST(f2, tp2, b); 184 ICOPY_ELT(f1, tp2, i); 185 } else { 186 CCOPY_LIST(f2, tp2, b); 187 CCOPY_ELT(f1, tp2, i); 188 } 189 } else { 190 if (iflag) { 191 ICOPY_LIST(f1, tp2, b); 192 ICOPY_ELT(f2, tp2, i); 193 } else { 194 CCOPY_LIST(f1, tp2, b); 195 CCOPY_ELT(f2, tp2, i); 196 } 197 } 198 } 199 if (f2 < l2) { 200 if (iflag) 201 ICOPY_LIST(f2, tp2, l2); 202 else 203 CCOPY_LIST(f2, tp2, l2); 204 } else if (f1 < l1) { 205 if (iflag) 206 ICOPY_LIST(f1, tp2, l1); 207 else 208 CCOPY_LIST(f1, tp2, l1); 209 } 210 *p1 = l2; 211 } 212 tp2 = list1; /* swap list1, list2 */ 213 list1 = list2; 214 list2 = tp2; 215 last = list2 + nmemb*size; 216 } 217 if (base == list2) { 218 memmove(list2, list1, nmemb*size); 219 list2 = list1; 220 } 221 free(list2); 222 return (0); 223 } 224 225 #define swap(a, b) { \ 226 s = b; \ 227 i = size; \ 228 do { \ 229 tmp = *a; *a++ = *s; *s++ = tmp; \ 230 } while (--i); \ 231 a -= size; \ 232 } 233 #define reverse(bot, top) { \ 234 s = top; \ 235 do { \ 236 i = size; \ 237 do { \ 238 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 239 } while (--i); \ 240 s -= size2; \ 241 } while(bot < s); \ 242 } 243 244 /* 245 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 246 * increasing order, list2 in a corresponding linked list. Checks for runs 247 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 248 * is defined. Otherwise simple pairwise merging is used.) 249 */ 250 void 251 setup(u_char *list1, u_char *list2, size_t n, size_t size, 252 int (*cmp)(const void *, const void *)) 253 { 254 int i, length, size2, sense; 255 u_char tmp, *f1, *f2, *s, *l2, *last, *p2; 256 257 size2 = size*2; 258 if (n <= 5) { 259 insertionsort(list1, n, size, cmp); 260 *EVAL(list2) = (u_char*) list2 + n*size; 261 return; 262 } 263 /* 264 * Avoid running pointers out of bounds; limit n to evens 265 * for simplicity. 266 */ 267 i = 4 + (n & 1); 268 insertionsort(list1 + (n - i) * size, i, size, cmp); 269 last = list1 + size * (n - i); 270 *EVAL(list2 + (last - list1)) = list2 + n * size; 271 272 #ifdef NATURAL 273 p2 = list2; 274 f1 = list1; 275 sense = (cmp(f1, f1 + size) > 0); 276 for (; f1 < last; sense = !sense) { 277 length = 2; 278 /* Find pairs with same sense. */ 279 for (f2 = f1 + size2; f2 < last; f2 += size2) { 280 if ((cmp(f2, f2+ size) > 0) != sense) 281 break; 282 length += 2; 283 } 284 if (length < THRESHOLD) { /* Pairwise merge */ 285 do { 286 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 287 if (sense > 0) 288 swap (f1, f1 + size); 289 } while ((f1 += size2) < f2); 290 } else { /* Natural merge */ 291 l2 = f2; 292 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 293 if ((cmp(f2-size, f2) > 0) != sense) { 294 p2 = *EVAL(p2) = f2 - list1 + list2; 295 if (sense > 0) 296 reverse(f1, f2-size); 297 f1 = f2; 298 } 299 } 300 if (sense > 0) 301 reverse (f1, f2-size); 302 f1 = f2; 303 if (f2 < last || cmp(f2 - size, f2) > 0) 304 p2 = *EVAL(p2) = f2 - list1 + list2; 305 else 306 p2 = *EVAL(p2) = list2 + n*size; 307 } 308 } 309 #else /* pairwise merge only. */ 310 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 311 p2 = *EVAL(p2) = p2 + size2; 312 if (cmp (f1, f1 + size) > 0) 313 swap(f1, f1 + size); 314 } 315 #endif /* NATURAL */ 316 } 317 318 /* 319 * This is to avoid out-of-bounds addresses in sorting the 320 * last 4 elements. 321 */ 322 static void 323 insertionsort(u_char *a, size_t n, size_t size, 324 int (*cmp)(const void *, const void *)) 325 { 326 u_char *ai, *s, *t, *u, tmp; 327 int i; 328 329 for (ai = a+size; --n >= 1; ai += size) 330 for (t = ai; t > a; t -= size) { 331 u = t - size; 332 if (cmp(u, t) <= 0) 333 break; 334 swap(u, t); 335 } 336 } 337