merge.c revision 1.6
1 /* $NetBSD: merge.c,v 1.6 1998/02/03 18:44:17 perry Exp $ */ 2 3 /*- 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Peter McIlroy. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "from: @(#)merge.c 8.2 (Berkeley) 2/14/94"; 43 #else 44 __RCSID("$NetBSD: merge.c,v 1.6 1998/02/03 18:44:17 perry Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 /* 49 * Hybrid exponential search/linear search merge sort with hybrid 50 * natural/pairwise first pass. Requires about .3% more comparisons 51 * for random data than LSMS with pairwise first pass alone. 52 * It works for objects as small as two bytes. 53 */ 54 55 #define NATURAL 56 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ 57 58 /* #define NATURAL to get hybrid natural merge. 59 * (The default is pairwise merging.) 60 */ 61 62 #include "namespace.h" 63 #include <sys/types.h> 64 65 #include <errno.h> 66 #include <stdlib.h> 67 #include <string.h> 68 69 #ifdef __weak_alias 70 __weak_alias(mergesort,_mergesort); 71 #endif 72 73 static void setup __P((u_char *, u_char *, size_t, size_t, 74 int (*)(const void *, const void *))); 75 static void insertionsort __P((u_char *, size_t, size_t, 76 int (*)(const void *, const void *))); 77 78 #define ISIZE sizeof(int) 79 #define PSIZE sizeof(u_char *) 80 #define ICOPY_LIST(src, dst, last) \ 81 do \ 82 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ 83 while(src < last) 84 #define ICOPY_ELT(src, dst, i) \ 85 do \ 86 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ 87 while (i -= ISIZE) 88 89 #define CCOPY_LIST(src, dst, last) \ 90 do \ 91 *dst++ = *src++; \ 92 while (src < last) 93 #define CCOPY_ELT(src, dst, i) \ 94 do \ 95 *dst++ = *src++; \ 96 while (i -= 1) 97 98 /* 99 * Find the next possible pointer head. (Trickery for forcing an array 100 * to do double duty as a linked list when objects do not align with word 101 * boundaries. 102 */ 103 /* Assumption: PSIZE is a power of 2. */ 104 #define EVAL(p) (u_char **) \ 105 ((u_char *)0 + \ 106 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))) 107 108 /* 109 * Arguments are as for qsort. 110 */ 111 int 112 mergesort(base, nmemb, size, cmp) 113 void *base; 114 size_t nmemb; 115 size_t size; 116 int (*cmp) __P((const void *, const void *)); 117 { 118 int i, sense; 119 int big, iflag; 120 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 121 u_char *list2, *list1, *p2, *p, *last, **p1; 122 123 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 124 errno = EINVAL; 125 return (-1); 126 } 127 128 /* 129 * XXX 130 * Stupid subtraction for the Cray. 131 */ 132 iflag = 0; 133 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 134 iflag = 1; 135 136 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 137 return (-1); 138 139 list1 = base; 140 setup(list1, list2, nmemb, size, cmp); 141 last = list2 + nmemb * size; 142 i = big = 0; 143 while (*EVAL(list2) != last) { 144 l2 = list1; 145 p1 = EVAL(list1); 146 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 147 p2 = *EVAL(p2); 148 f1 = l2; 149 f2 = l1 = list1 + (p2 - list2); 150 if (p2 != last) 151 p2 = *EVAL(p2); 152 l2 = list1 + (p2 - list2); 153 while (f1 < l1 && f2 < l2) { 154 if ((*cmp)(f1, f2) <= 0) { 155 q = f2; 156 b = f1, t = l1; 157 sense = -1; 158 } else { 159 q = f1; 160 b = f2, t = l2; 161 sense = 0; 162 } 163 if (!big) { /* here i = 0 */ 164 #if 0 165 LINEAR: 166 #endif 167 while ((b += size) < t && cmp(q, b) >sense) 168 if (++i == 6) { 169 big = 1; 170 goto EXPONENTIAL; 171 } 172 } else { 173 EXPONENTIAL: for (i = size; ; i <<= 1) 174 if ((p = (b + i)) >= t) { 175 if ((p = t - size) > b && 176 (*cmp)(q, p) <= sense) 177 t = p; 178 else 179 b = p; 180 break; 181 } else if ((*cmp)(q, p) <= sense) { 182 t = p; 183 if (i == size) 184 big = 0; 185 goto FASTCASE; 186 } else 187 b = p; 188 #if 0 189 SLOWCASE: 190 #endif 191 while (t > b+size) { 192 i = (((t - b) / size) >> 1) * size; 193 if ((*cmp)(q, p = b + i) <= sense) 194 t = p; 195 else 196 b = p; 197 } 198 goto COPY; 199 FASTCASE: while (i > size) 200 if ((*cmp)(q, 201 p = b + (i >>= 1)) <= sense) 202 t = p; 203 else 204 b = p; 205 COPY: b = t; 206 } 207 i = size; 208 if (q == f1) { 209 if (iflag) { 210 ICOPY_LIST(f2, tp2, b); 211 ICOPY_ELT(f1, tp2, i); 212 } else { 213 CCOPY_LIST(f2, tp2, b); 214 CCOPY_ELT(f1, tp2, i); 215 } 216 } else { 217 if (iflag) { 218 ICOPY_LIST(f1, tp2, b); 219 ICOPY_ELT(f2, tp2, i); 220 } else { 221 CCOPY_LIST(f1, tp2, b); 222 CCOPY_ELT(f2, tp2, i); 223 } 224 } 225 } 226 if (f2 < l2) { 227 if (iflag) 228 ICOPY_LIST(f2, tp2, l2); 229 else 230 CCOPY_LIST(f2, tp2, l2); 231 } else if (f1 < l1) { 232 if (iflag) 233 ICOPY_LIST(f1, tp2, l1); 234 else 235 CCOPY_LIST(f1, tp2, l1); 236 } 237 *p1 = l2; 238 } 239 tp2 = list1; /* swap list1, list2 */ 240 list1 = list2; 241 list2 = tp2; 242 last = list2 + nmemb*size; 243 } 244 if (base == list2) { 245 memmove(list2, list1, nmemb*size); 246 list2 = list1; 247 } 248 free(list2); 249 return (0); 250 } 251 252 #define swap(a, b) { \ 253 s = b; \ 254 i = size; \ 255 do { \ 256 tmp = *a; *a++ = *s; *s++ = tmp; \ 257 } while (--i); \ 258 a -= size; \ 259 } 260 #define reverse(bot, top) { \ 261 s = top; \ 262 do { \ 263 i = size; \ 264 do { \ 265 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 266 } while (--i); \ 267 s -= size2; \ 268 } while(bot < s); \ 269 } 270 271 /* 272 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 273 * increasing order, list2 in a corresponding linked list. Checks for runs 274 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 275 * is defined. Otherwise simple pairwise merging is used.) 276 */ 277 void 278 setup(list1, list2, n, size, cmp) 279 size_t n, size; 280 int (*cmp) __P((const void *, const void *)); 281 u_char *list1, *list2; 282 { 283 int i, length, size2, tmp, sense; 284 u_char *f1, *f2, *s, *l2, *last, *p2; 285 286 size2 = size*2; 287 if (n <= 5) { 288 insertionsort(list1, n, size, cmp); 289 *EVAL(list2) = (u_char*) list2 + n*size; 290 return; 291 } 292 /* 293 * Avoid running pointers out of bounds; limit n to evens 294 * for simplicity. 295 */ 296 i = 4 + (n & 1); 297 insertionsort(list1 + (n - i) * size, i, size, cmp); 298 last = list1 + size * (n - i); 299 *EVAL(list2 + (last - list1)) = list2 + n * size; 300 301 #ifdef NATURAL 302 p2 = list2; 303 f1 = list1; 304 sense = (cmp(f1, f1 + size) > 0); 305 for (; f1 < last; sense = !sense) { 306 length = 2; 307 /* Find pairs with same sense. */ 308 for (f2 = f1 + size2; f2 < last; f2 += size2) { 309 if ((cmp(f2, f2+ size) > 0) != sense) 310 break; 311 length += 2; 312 } 313 if (length < THRESHOLD) { /* Pairwise merge */ 314 do { 315 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 316 if (sense > 0) 317 swap (f1, f1 + size); 318 } while ((f1 += size2) < f2); 319 } else { /* Natural merge */ 320 l2 = f2; 321 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 322 if ((cmp(f2-size, f2) > 0) != sense) { 323 p2 = *EVAL(p2) = f2 - list1 + list2; 324 if (sense > 0) 325 reverse(f1, f2-size); 326 f1 = f2; 327 } 328 } 329 if (sense > 0) 330 reverse (f1, f2-size); 331 f1 = f2; 332 if (f2 < last || cmp(f2 - size, f2) > 0) 333 p2 = *EVAL(p2) = f2 - list1 + list2; 334 else 335 p2 = *EVAL(p2) = list2 + n*size; 336 } 337 } 338 #else /* pairwise merge only. */ 339 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 340 p2 = *EVAL(p2) = p2 + size2; 341 if (cmp (f1, f1 + size) > 0) 342 swap(f1, f1 + size); 343 } 344 #endif /* NATURAL */ 345 } 346 347 /* 348 * This is to avoid out-of-bounds addresses in sorting the 349 * last 4 elements. 350 */ 351 static void 352 insertionsort(a, n, size, cmp) 353 u_char *a; 354 size_t n, size; 355 int (*cmp) __P((const void *, const void *)); 356 { 357 u_char *ai, *s, *t, *u, tmp; 358 int i; 359 360 for (ai = a+size; --n >= 1; ai += size) 361 for (t = ai; t > a; t -= size) { 362 u = t - size; 363 if (cmp(u, t) <= 0) 364 break; 365 swap(u, t); 366 } 367 } 368
Indexes created Tue Sep 23 20:09:58 GMT 2025