1 /* $NetBSD: merge.c,v 1.11 2003/08/07 16:43:42 agc 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "from: @(#)merge.c 8.2 (Berkeley) 2/14/94"; 39 #else 40 __RCSID("$NetBSD: merge.c,v 1.11 2003/08/07 16:43:42 agc Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 /* 45 * Hybrid exponential search/linear search merge sort with hybrid 46 * natural/pairwise first pass. Requires about .3% more comparisons 47 * for random data than LSMS with pairwise first pass alone. 48 * It works for objects as small as two bytes. 49 */ 50 51 #define NATURAL 52 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ 53 54 /* #define NATURAL to get hybrid natural merge. 55 * (The default is pairwise merging.) 56 */ 57 58 #include "namespace.h" 59 #include <sys/types.h> 60 61 #include <assert.h> 62 #include <errno.h> 63 #include <stdlib.h> 64 #include <string.h> 65 66 #ifdef __weak_alias 67 __weak_alias(mergesort,_mergesort) 68 #endif 69 70 static void setup __P((u_char *, u_char *, size_t, size_t, 71 int (*)(const void *, const void *))); 72 static void insertionsort __P((u_char *, size_t, size_t, 73 int (*)(const void *, const void *))); 74 75 #define ISIZE sizeof(int) 76 #define PSIZE sizeof(u_char *) 77 #define ICOPY_LIST(src, dst, last) \ 78 do \ 79 *(int*)(void *)dst = *(int*)(void *)src, \ 80 src += ISIZE, dst += ISIZE; \ 81 while(src < last) 82 #define ICOPY_ELT(src, dst, i) \ 83 do \ 84 *(int*)(void *)dst = *(int*)(void *)src, \ 85 src += ISIZE, dst += ISIZE; \ 86 while (i -= ISIZE) 87 88 #define CCOPY_LIST(src, dst, last) \ 89 do \ 90 *dst++ = *src++; \ 91 while (src < last) 92 #define CCOPY_ELT(src, dst, i) \ 93 do \ 94 *dst++ = *src++; \ 95 while (i -= 1) 96 97 /* 98 * Find the next possible pointer head. (Trickery for forcing an array 99 * to do double duty as a linked list when objects do not align with word 100 * boundaries. 101 */ 102 /* Assumption: PSIZE is a power of 2. */ 103 #define EVAL(p) ((u_char **)(void *) \ 104 ((u_char *)0 + \ 105 (((u_char *)(void *)(p) + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))) 106 107 /* 108 * Arguments are as for qsort. 109 */ 110 int 111 mergesort(base, nmemb, size, cmp) 112 void *base; 113 size_t nmemb; 114 size_t size; 115 int (*cmp) __P((const void *, const void *)); 116 { 117 int i, sense; 118 int big, iflag; 119 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 120 u_char *list2, *list1, *p2, *p, *last, **p1; 121 122 _DIAGASSERT(base != NULL); 123 _DIAGASSERT(cmp != NULL); 124 125 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 126 errno = EINVAL; 127 return (-1); 128 } 129 130 /* 131 * XXX 132 * Stupid subtraction for the Cray. 133 */ 134 iflag = 0; 135 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 136 iflag = 1; 137 138 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 139 return (-1); 140 141 list1 = base; 142 setup(list1, list2, nmemb, size, cmp); 143 last = list2 + nmemb * size; 144 i = big = 0; 145 while (*EVAL(list2) != last) { 146 l2 = list1; 147 p1 = EVAL(list1); 148 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 149 p2 = *EVAL(p2); 150 f1 = l2; 151 f2 = l1 = list1 + (p2 - list2); 152 if (p2 != last) 153 p2 = *EVAL(p2); 154 l2 = list1 + (p2 - list2); 155 while (f1 < l1 && f2 < l2) { 156 if ((*cmp)(f1, f2) <= 0) { 157 q = f2; 158 b = f1, t = l1; 159 sense = -1; 160 } else { 161 q = f1; 162 b = f2, t = l2; 163 sense = 0; 164 } 165 if (!big) { /* here i = 0 */ 166 #if 0 167 LINEAR: 168 #endif 169 while ((b += size) < t && cmp(q, b) >sense) 170 if (++i == 6) { 171 big = 1; 172 goto EXPONENTIAL; 173 } 174 } else { 175 EXPONENTIAL: for (i = size; ; i <<= 1) 176 if ((p = (b + i)) >= t) { 177 if ((p = t - size) > b && 178 (*cmp)(q, p) <= sense) 179 t = p; 180 else 181 b = p; 182 break; 183 } else if ((*cmp)(q, p) <= sense) { 184 t = p; 185 if (i == size) 186 big = 0; 187 goto FASTCASE; 188 } else 189 b = p; 190 #if 0 191 SLOWCASE: 192 #endif 193 while (t > b+size) { 194 i = (((t - b) / size) >> 1) * size; 195 if ((*cmp)(q, p = b + i) <= sense) 196 t = p; 197 else 198 b = p; 199 } 200 goto COPY; 201 FASTCASE: while (i > size) 202 if ((*cmp)(q, 203 p = b + 204 (i = (unsigned int) i >> 1)) <= sense) 205 t = p; 206 else 207 b = p; 208 COPY: b = t; 209 } 210 i = size; 211 if (q == f1) { 212 if (iflag) { 213 ICOPY_LIST(f2, tp2, b); 214 ICOPY_ELT(f1, tp2, i); 215 } else { 216 CCOPY_LIST(f2, tp2, b); 217 CCOPY_ELT(f1, tp2, i); 218 } 219 } else { 220 if (iflag) { 221 ICOPY_LIST(f1, tp2, b); 222 ICOPY_ELT(f2, tp2, i); 223 } else { 224 CCOPY_LIST(f1, tp2, b); 225 CCOPY_ELT(f2, tp2, i); 226 } 227 } 228 } 229 if (f2 < l2) { 230 if (iflag) 231 ICOPY_LIST(f2, tp2, l2); 232 else 233 CCOPY_LIST(f2, tp2, l2); 234 } else if (f1 < l1) { 235 if (iflag) 236 ICOPY_LIST(f1, tp2, l1); 237 else 238 CCOPY_LIST(f1, tp2, l1); 239 } 240 *p1 = l2; 241 } 242 tp2 = list1; /* swap list1, list2 */ 243 list1 = list2; 244 list2 = tp2; 245 last = list2 + nmemb*size; 246 } 247 if (base == list2) { 248 memmove(list2, list1, nmemb*size); 249 list2 = list1; 250 } 251 free(list2); 252 return (0); 253 } 254 255 #define swap(a, b) { \ 256 s = b; \ 257 i = size; \ 258 do { \ 259 tmp = *a; *a++ = *s; *s++ = tmp; \ 260 } while (--i); \ 261 a -= size; \ 262 } 263 #define reverse(bot, top) { \ 264 s = top; \ 265 do { \ 266 i = size; \ 267 do { \ 268 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 269 } while (--i); \ 270 s -= size2; \ 271 } while(bot < s); \ 272 } 273 274 /* 275 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 276 * increasing order, list2 in a corresponding linked list. Checks for runs 277 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 278 * is defined. Otherwise simple pairwise merging is used.) 279 */ 280 281 /* XXX: shouldn't this function be static? - lukem 990810 */ 282 void 283 setup(list1, list2, n, size, cmp) 284 size_t n, size; 285 int (*cmp) __P((const void *, const void *)); 286 u_char *list1, *list2; 287 { 288 int i, length, size2, tmp, sense; 289 u_char *f1, *f2, *s, *l2, *last, *p2; 290 291 _DIAGASSERT(cmp != NULL); 292 _DIAGASSERT(list1 != NULL); 293 _DIAGASSERT(list2 != NULL); 294 295 size2 = size*2; 296 if (n <= 5) { 297 insertionsort(list1, n, size, cmp); 298 *EVAL(list2) = list2 + n*size; 299 return; 300 } 301 /* 302 * Avoid running pointers out of bounds; limit n to evens 303 * for simplicity. 304 */ 305 i = 4 + (n & 1); 306 insertionsort(list1 + (n - i) * size, (size_t)i, size, cmp); 307 last = list1 + size * (n - i); 308 *EVAL(list2 + (last - list1)) = list2 + n * size; 309 310 #ifdef NATURAL 311 p2 = list2; 312 f1 = list1; 313 sense = (cmp(f1, f1 + size) > 0); 314 for (; f1 < last; sense = !sense) { 315 length = 2; 316 /* Find pairs with same sense. */ 317 for (f2 = f1 + size2; f2 < last; f2 += size2) { 318 if ((cmp(f2, f2+ size) > 0) != sense) 319 break; 320 length += 2; 321 } 322 if (length < THRESHOLD) { /* Pairwise merge */ 323 do { 324 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 325 if (sense > 0) 326 swap (f1, f1 + size); 327 } while ((f1 += size2) < f2); 328 } else { /* Natural merge */ 329 l2 = f2; 330 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 331 if ((cmp(f2-size, f2) > 0) != sense) { 332 p2 = *EVAL(p2) = f2 - list1 + list2; 333 if (sense > 0) 334 reverse(f1, f2-size); 335 f1 = f2; 336 } 337 } 338 if (sense > 0) 339 reverse (f1, f2-size); 340 f1 = f2; 341 if (f2 < last || cmp(f2 - size, f2) > 0) 342 p2 = *EVAL(p2) = f2 - list1 + list2; 343 else 344 p2 = *EVAL(p2) = list2 + n*size; 345 } 346 } 347 #else /* pairwise merge only. */ 348 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 349 p2 = *EVAL(p2) = p2 + size2; 350 if (cmp (f1, f1 + size) > 0) 351 swap(f1, f1 + size); 352 } 353 #endif /* NATURAL */ 354 } 355 356 /* 357 * This is to avoid out-of-bounds addresses in sorting the 358 * last 4 elements. 359 */ 360 static void 361 insertionsort(a, n, size, cmp) 362 u_char *a; 363 size_t n, size; 364 int (*cmp) __P((const void *, const void *)); 365 { 366 u_char *ai, *s, *t, *u, tmp; 367 int i; 368 369 _DIAGASSERT(a != NULL); 370 _DIAGASSERT(cmp != NULL); 371 372 for (ai = a+size; --n >= 1; ai += size) 373 for (t = ai; t > a; t -= size) { 374 u = t - size; 375 if (cmp(u, t) <= 0) 376 break; 377 swap(u, t); 378 } 379 } 380