1 /* $NetBSD: merge.c,v 1.12 2009/02/12 03:12:36 lukem 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 1.12 2009/02/12 03:12:36 lukem 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 size_t i; 118 int 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 _DIAGASSERT(base != NULL); 124 _DIAGASSERT(cmp != NULL); 125 126 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 127 errno = EINVAL; 128 return (-1); 129 } 130 131 /* 132 * XXX 133 * Stupid subtraction for the Cray. 134 */ 135 iflag = 0; 136 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 137 iflag = 1; 138 139 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 140 return (-1); 141 142 list1 = base; 143 setup(list1, list2, nmemb, size, cmp); 144 last = list2 + nmemb * size; 145 i = big = 0; 146 while (*EVAL(list2) != last) { 147 l2 = list1; 148 p1 = EVAL(list1); 149 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 150 p2 = *EVAL(p2); 151 f1 = l2; 152 f2 = l1 = list1 + (p2 - list2); 153 if (p2 != last) 154 p2 = *EVAL(p2); 155 l2 = list1 + (p2 - list2); 156 while (f1 < l1 && f2 < l2) { 157 if ((*cmp)(f1, f2) <= 0) { 158 q = f2; 159 b = f1, t = l1; 160 sense = -1; 161 } else { 162 q = f1; 163 b = f2, t = l2; 164 sense = 0; 165 } 166 if (!big) { /* here i = 0 */ 167 #if 0 168 LINEAR: 169 #endif 170 while ((b += size) < t && cmp(q, b) >sense) 171 if (++i == 6) { 172 big = 1; 173 goto EXPONENTIAL; 174 } 175 } else { 176 EXPONENTIAL: for (i = size; ; i <<= 1) 177 if ((p = (b + i)) >= t) { 178 if ((p = t - size) > b && 179 (*cmp)(q, p) <= sense) 180 t = p; 181 else 182 b = p; 183 break; 184 } else if ((*cmp)(q, p) <= sense) { 185 t = p; 186 if (i == size) 187 big = 0; 188 goto FASTCASE; 189 } else 190 b = p; 191 #if 0 192 SLOWCASE: 193 #endif 194 while (t > b+size) { 195 i = (((t - b) / size) >> 1) * size; 196 if ((*cmp)(q, p = b + i) <= sense) 197 t = p; 198 else 199 b = p; 200 } 201 goto COPY; 202 FASTCASE: while (i > size) 203 if ((*cmp)(q, 204 p = b + 205 (i = (unsigned int) i >> 1)) <= sense) 206 t = p; 207 else 208 b = p; 209 COPY: b = t; 210 } 211 i = size; 212 if (q == f1) { 213 if (iflag) { 214 ICOPY_LIST(f2, tp2, b); 215 ICOPY_ELT(f1, tp2, i); 216 } else { 217 CCOPY_LIST(f2, tp2, b); 218 CCOPY_ELT(f1, tp2, i); 219 } 220 } else { 221 if (iflag) { 222 ICOPY_LIST(f1, tp2, b); 223 ICOPY_ELT(f2, tp2, i); 224 } else { 225 CCOPY_LIST(f1, tp2, b); 226 CCOPY_ELT(f2, tp2, i); 227 } 228 } 229 } 230 if (f2 < l2) { 231 if (iflag) 232 ICOPY_LIST(f2, tp2, l2); 233 else 234 CCOPY_LIST(f2, tp2, l2); 235 } else if (f1 < l1) { 236 if (iflag) 237 ICOPY_LIST(f1, tp2, l1); 238 else 239 CCOPY_LIST(f1, tp2, l1); 240 } 241 *p1 = l2; 242 } 243 tp2 = list1; /* swap list1, list2 */ 244 list1 = list2; 245 list2 = tp2; 246 last = list2 + nmemb*size; 247 } 248 if (base == list2) { 249 memmove(list2, list1, nmemb*size); 250 list2 = list1; 251 } 252 free(list2); 253 return (0); 254 } 255 256 #define swap(a, b) { \ 257 s = b; \ 258 i = size; \ 259 do { \ 260 tmp = *a; *a++ = *s; *s++ = tmp; \ 261 } while (--i); \ 262 a -= size; \ 263 } 264 #define reverse(bot, top) { \ 265 s = top; \ 266 do { \ 267 i = size; \ 268 do { \ 269 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 270 } while (--i); \ 271 s -= size2; \ 272 } while(bot < s); \ 273 } 274 275 /* 276 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 277 * increasing order, list2 in a corresponding linked list. Checks for runs 278 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 279 * is defined. Otherwise simple pairwise merging is used.) 280 */ 281 282 /* XXX: shouldn't this function be static? - lukem 990810 */ 283 void 284 setup(list1, list2, n, size, cmp) 285 size_t n, size; 286 int (*cmp) __P((const void *, const void *)); 287 u_char *list1, *list2; 288 { 289 int i, length, size2, tmp, sense; 290 u_char *f1, *f2, *s, *l2, *last, *p2; 291 292 _DIAGASSERT(cmp != NULL); 293 _DIAGASSERT(list1 != NULL); 294 _DIAGASSERT(list2 != NULL); 295 296 size2 = size*2; 297 if (n <= 5) { 298 insertionsort(list1, n, size, cmp); 299 *EVAL(list2) = list2 + n*size; 300 return; 301 } 302 /* 303 * Avoid running pointers out of bounds; limit n to evens 304 * for simplicity. 305 */ 306 i = 4 + (n & 1); 307 insertionsort(list1 + (n - i) * size, (size_t)i, size, cmp); 308 last = list1 + size * (n - i); 309 *EVAL(list2 + (last - list1)) = list2 + n * size; 310 311 #ifdef NATURAL 312 p2 = list2; 313 f1 = list1; 314 sense = (cmp(f1, f1 + size) > 0); 315 for (; f1 < last; sense = !sense) { 316 length = 2; 317 /* Find pairs with same sense. */ 318 for (f2 = f1 + size2; f2 < last; f2 += size2) { 319 if ((cmp(f2, f2+ size) > 0) != sense) 320 break; 321 length += 2; 322 } 323 if (length < THRESHOLD) { /* Pairwise merge */ 324 do { 325 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 326 if (sense > 0) 327 swap (f1, f1 + size); 328 } while ((f1 += size2) < f2); 329 } else { /* Natural merge */ 330 l2 = f2; 331 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 332 if ((cmp(f2-size, f2) > 0) != sense) { 333 p2 = *EVAL(p2) = f2 - list1 + list2; 334 if (sense > 0) 335 reverse(f1, f2-size); 336 f1 = f2; 337 } 338 } 339 if (sense > 0) 340 reverse (f1, f2-size); 341 f1 = f2; 342 if (f2 < last || cmp(f2 - size, f2) > 0) 343 p2 = *EVAL(p2) = f2 - list1 + list2; 344 else 345 p2 = *EVAL(p2) = list2 + n*size; 346 } 347 } 348 #else /* pairwise merge only. */ 349 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 350 p2 = *EVAL(p2) = p2 + size2; 351 if (cmp (f1, f1 + size) > 0) 352 swap(f1, f1 + size); 353 } 354 #endif /* NATURAL */ 355 } 356 357 /* 358 * This is to avoid out-of-bounds addresses in sorting the 359 * last 4 elements. 360 */ 361 static void 362 insertionsort(a, n, size, cmp) 363 u_char *a; 364 size_t n, size; 365 int (*cmp) __P((const void *, const void *)); 366 { 367 u_char *ai, *s, *t, *u, tmp; 368 int i; 369 370 _DIAGASSERT(a != NULL); 371 _DIAGASSERT(cmp != NULL); 372 373 for (ai = a+size; --n >= 1; ai += size) 374 for (t = ai; t > a; t -= size) { 375 u = t - size; 376 if (cmp(u, t) <= 0) 377 break; 378 swap(u, t); 379 } 380 } 381