1 /* $OpenBSD: merge.c,v 1.8 2005/08/08 08:05:37 espie 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 /* 105 * XXX 106 * Stupid subtraction for the Cray. 107 */ 108 iflag = 0; 109 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 110 iflag = 1; 111 112 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 113 return (-1); 114 115 list1 = base; 116 setup(list1, list2, nmemb, size, cmp); 117 last = list2 + nmemb * size; 118 i = big = 0; 119 while (*EVAL(list2) != last) { 120 l2 = list1; 121 p1 = EVAL(list1); 122 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 123 p2 = *EVAL(p2); 124 f1 = l2; 125 f2 = l1 = list1 + (p2 - list2); 126 if (p2 != last) 127 p2 = *EVAL(p2); 128 l2 = list1 + (p2 - list2); 129 while (f1 < l1 && f2 < l2) { 130 if ((*cmp)(f1, f2) <= 0) { 131 q = f2; 132 b = f1, t = l1; 133 sense = -1; 134 } else { 135 q = f1; 136 b = f2, t = l2; 137 sense = 0; 138 } 139 if (!big) { /* here i = 0 */ 140 while ((b += size) < t && cmp(q, b) >sense) 141 if (++i == 6) { 142 big = 1; 143 goto EXPONENTIAL; 144 } 145 } else { 146 EXPONENTIAL: for (i = size; ; i <<= 1) 147 if ((p = (b + i)) >= t) { 148 if ((p = t - size) > b && 149 (*cmp)(q, p) <= sense) 150 t = p; 151 else 152 b = p; 153 break; 154 } else if ((*cmp)(q, p) <= sense) { 155 t = p; 156 if (i == size) 157 big = 0; 158 goto FASTCASE; 159 } else 160 b = p; 161 while (t > b+size) { 162 i = (((t - b) / size) >> 1) * size; 163 if ((*cmp)(q, p = b + i) <= sense) 164 t = p; 165 else 166 b = p; 167 } 168 goto COPY; 169 FASTCASE: while (i > size) 170 if ((*cmp)(q, 171 p = b + (i >>= 1)) <= sense) 172 t = p; 173 else 174 b = p; 175 COPY: b = t; 176 } 177 i = size; 178 if (q == f1) { 179 if (iflag) { 180 ICOPY_LIST(f2, tp2, b); 181 ICOPY_ELT(f1, tp2, i); 182 } else { 183 CCOPY_LIST(f2, tp2, b); 184 CCOPY_ELT(f1, tp2, i); 185 } 186 } else { 187 if (iflag) { 188 ICOPY_LIST(f1, tp2, b); 189 ICOPY_ELT(f2, tp2, i); 190 } else { 191 CCOPY_LIST(f1, tp2, b); 192 CCOPY_ELT(f2, tp2, i); 193 } 194 } 195 } 196 if (f2 < l2) { 197 if (iflag) 198 ICOPY_LIST(f2, tp2, l2); 199 else 200 CCOPY_LIST(f2, tp2, l2); 201 } else if (f1 < l1) { 202 if (iflag) 203 ICOPY_LIST(f1, tp2, l1); 204 else 205 CCOPY_LIST(f1, tp2, l1); 206 } 207 *p1 = l2; 208 } 209 tp2 = list1; /* swap list1, list2 */ 210 list1 = list2; 211 list2 = tp2; 212 last = list2 + nmemb*size; 213 } 214 if (base == list2) { 215 memmove(list2, list1, nmemb*size); 216 list2 = list1; 217 } 218 free(list2); 219 return (0); 220 } 221 222 #define swap(a, b) { \ 223 s = b; \ 224 i = size; \ 225 do { \ 226 tmp = *a; *a++ = *s; *s++ = tmp; \ 227 } while (--i); \ 228 a -= size; \ 229 } 230 #define reverse(bot, top) { \ 231 s = top; \ 232 do { \ 233 i = size; \ 234 do { \ 235 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 236 } while (--i); \ 237 s -= size2; \ 238 } while(bot < s); \ 239 } 240 241 /* 242 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 243 * increasing order, list2 in a corresponding linked list. Checks for runs 244 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 245 * is defined. Otherwise simple pairwise merging is used.) 246 */ 247 void 248 setup(u_char *list1, u_char *list2, size_t n, size_t size, 249 int (*cmp)(const void *, const void *)) 250 { 251 int i, length, size2, tmp, sense; 252 u_char *f1, *f2, *s, *l2, *last, *p2; 253 254 size2 = size*2; 255 if (n <= 5) { 256 insertionsort(list1, n, size, cmp); 257 *EVAL(list2) = (u_char*) list2 + n*size; 258 return; 259 } 260 /* 261 * Avoid running pointers out of bounds; limit n to evens 262 * for simplicity. 263 */ 264 i = 4 + (n & 1); 265 insertionsort(list1 + (n - i) * size, i, size, cmp); 266 last = list1 + size * (n - i); 267 *EVAL(list2 + (last - list1)) = list2 + n * size; 268 269 #ifdef NATURAL 270 p2 = list2; 271 f1 = list1; 272 sense = (cmp(f1, f1 + size) > 0); 273 for (; f1 < last; sense = !sense) { 274 length = 2; 275 /* Find pairs with same sense. */ 276 for (f2 = f1 + size2; f2 < last; f2 += size2) { 277 if ((cmp(f2, f2+ size) > 0) != sense) 278 break; 279 length += 2; 280 } 281 if (length < THRESHOLD) { /* Pairwise merge */ 282 do { 283 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 284 if (sense > 0) 285 swap (f1, f1 + size); 286 } while ((f1 += size2) < f2); 287 } else { /* Natural merge */ 288 l2 = f2; 289 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 290 if ((cmp(f2-size, f2) > 0) != sense) { 291 p2 = *EVAL(p2) = f2 - list1 + list2; 292 if (sense > 0) 293 reverse(f1, f2-size); 294 f1 = f2; 295 } 296 } 297 if (sense > 0) 298 reverse (f1, f2-size); 299 f1 = f2; 300 if (f2 < last || cmp(f2 - size, f2) > 0) 301 p2 = *EVAL(p2) = f2 - list1 + list2; 302 else 303 p2 = *EVAL(p2) = list2 + n*size; 304 } 305 } 306 #else /* pairwise merge only. */ 307 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 308 p2 = *EVAL(p2) = p2 + size2; 309 if (cmp (f1, f1 + size) > 0) 310 swap(f1, f1 + size); 311 } 312 #endif /* NATURAL */ 313 } 314 315 /* 316 * This is to avoid out-of-bounds addresses in sorting the 317 * last 4 elements. 318 */ 319 static void 320 insertionsort(u_char *a, size_t n, size_t size, 321 int (*cmp)(const void *, const void *)) 322 { 323 u_char *ai, *s, *t, *u, tmp; 324 int i; 325 326 for (ai = a+size; --n >= 1; ai += size) 327 for (t = ai; t > a; t -= size) { 328 u = t - size; 329 if (cmp(u, t) <= 0) 330 break; 331 swap(u, t); 332 } 333 } 334