1 /* $NetBSD: merge.c,v 1.7 1998/11/15 17:13:51 christos 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 1.7 1998/11/15 17:13:51 christos 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*)(void *)dst = *(int*)(void *)src, \ 83 src += ISIZE, dst += ISIZE; \ 84 while(src < last) 85 #define ICOPY_ELT(src, dst, i) \ 86 do \ 87 *(int*)(void *)dst = *(int*)(void *)src, \ 88 src += ISIZE, dst += ISIZE; \ 89 while (i -= ISIZE) 90 91 #define CCOPY_LIST(src, dst, last) \ 92 do \ 93 *dst++ = *src++; \ 94 while (src < last) 95 #define CCOPY_ELT(src, dst, i) \ 96 do \ 97 *dst++ = *src++; \ 98 while (i -= 1) 99 100 /* 101 * Find the next possible pointer head. (Trickery for forcing an array 102 * to do double duty as a linked list when objects do not align with word 103 * boundaries. 104 */ 105 /* Assumption: PSIZE is a power of 2. */ 106 #define EVAL(p) ((u_char **)(void *) \ 107 ((u_char *)0 + \ 108 (((u_char *)(void *)(p) + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))) 109 110 /* 111 * Arguments are as for qsort. 112 */ 113 int 114 mergesort(base, nmemb, size, cmp) 115 void *base; 116 size_t nmemb; 117 size_t size; 118 int (*cmp) __P((const void *, const void *)); 119 { 120 int i, sense; 121 int big, iflag; 122 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 123 u_char *list2, *list1, *p2, *p, *last, **p1; 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 void 281 setup(list1, list2, n, size, cmp) 282 size_t n, size; 283 int (*cmp) __P((const void *, const void *)); 284 u_char *list1, *list2; 285 { 286 int i, length, size2, tmp, sense; 287 u_char *f1, *f2, *s, *l2, *last, *p2; 288 289 size2 = size*2; 290 if (n <= 5) { 291 insertionsort(list1, n, size, cmp); 292 *EVAL(list2) = list2 + n*size; 293 return; 294 } 295 /* 296 * Avoid running pointers out of bounds; limit n to evens 297 * for simplicity. 298 */ 299 i = 4 + (n & 1); 300 insertionsort(list1 + (n - i) * size, (size_t)i, size, cmp); 301 last = list1 + size * (n - i); 302 *EVAL(list2 + (last - list1)) = list2 + n * size; 303 304 #ifdef NATURAL 305 p2 = list2; 306 f1 = list1; 307 sense = (cmp(f1, f1 + size) > 0); 308 for (; f1 < last; sense = !sense) { 309 length = 2; 310 /* Find pairs with same sense. */ 311 for (f2 = f1 + size2; f2 < last; f2 += size2) { 312 if ((cmp(f2, f2+ size) > 0) != sense) 313 break; 314 length += 2; 315 } 316 if (length < THRESHOLD) { /* Pairwise merge */ 317 do { 318 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 319 if (sense > 0) 320 swap (f1, f1 + size); 321 } while ((f1 += size2) < f2); 322 } else { /* Natural merge */ 323 l2 = f2; 324 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 325 if ((cmp(f2-size, f2) > 0) != sense) { 326 p2 = *EVAL(p2) = f2 - list1 + list2; 327 if (sense > 0) 328 reverse(f1, f2-size); 329 f1 = f2; 330 } 331 } 332 if (sense > 0) 333 reverse (f1, f2-size); 334 f1 = f2; 335 if (f2 < last || cmp(f2 - size, f2) > 0) 336 p2 = *EVAL(p2) = f2 - list1 + list2; 337 else 338 p2 = *EVAL(p2) = list2 + n*size; 339 } 340 } 341 #else /* pairwise merge only. */ 342 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 343 p2 = *EVAL(p2) = p2 + size2; 344 if (cmp (f1, f1 + size) > 0) 345 swap(f1, f1 + size); 346 } 347 #endif /* NATURAL */ 348 } 349 350 /* 351 * This is to avoid out-of-bounds addresses in sorting the 352 * last 4 elements. 353 */ 354 static void 355 insertionsort(a, n, size, cmp) 356 u_char *a; 357 size_t n, size; 358 int (*cmp) __P((const void *, const void *)); 359 { 360 u_char *ai, *s, *t, *u, tmp; 361 int i; 362 363 for (ai = a+size; --n >= 1; ai += size) 364 for (t = ai; t > a; t -= size) { 365 u = t - size; 366 if (cmp(u, t) <= 0) 367 break; 368 swap(u, t); 369 } 370 } 371