1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Peter McIlroy. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)merge.c 8.2 (Berkeley) 2/14/94 33 * $FreeBSD: src/lib/libc/stdlib/merge.c,v 1.8 2007/01/09 00:28:10 imp Exp $ 34 */ 35 36 /* 37 * Hybrid exponential search/linear search merge sort with hybrid 38 * natural/pairwise first pass. Requires about .3% more comparisons 39 * for random data than LSMS with pairwise first pass alone. 40 * It works for objects as small as two bytes. 41 */ 42 43 #define NATURAL 44 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ 45 46 /* #define NATURAL to get hybrid natural merge. 47 * (The default is pairwise merging.) 48 */ 49 50 #include <sys/param.h> 51 52 #include <errno.h> 53 #include <stdlib.h> 54 #include <string.h> 55 56 static void setup(u_char *, u_char *, size_t, size_t, 57 int (*)(const void *, const void *)); 58 static void insertionsort(u_char *, size_t, size_t, 59 int (*)(const void *, const void *)); 60 61 #define ISIZE sizeof(int) 62 #define PSIZE sizeof(u_char *) 63 #define ICOPY_LIST(src, dst, last) \ 64 do \ 65 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ 66 while(src < last) 67 #define ICOPY_ELT(src, dst, i) \ 68 do \ 69 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ 70 while (i -= ISIZE) 71 72 #define CCOPY_LIST(src, dst, last) \ 73 do \ 74 *dst++ = *src++; \ 75 while (src < last) 76 #define CCOPY_ELT(src, dst, i) \ 77 do \ 78 *dst++ = *src++; \ 79 while (i -= 1) 80 81 /* 82 * Find the next possible pointer head. (Trickery for forcing an array 83 * to do double duty as a linked list when objects do not align with word 84 * boundaries. 85 */ 86 /* Assumption: PSIZE is a power of 2. */ 87 #define EVAL(p) (u_char **) \ 88 ((u_char *)0 + \ 89 (rounddown2((u_char *)p + PSIZE - 1 - (u_char *)0, PSIZE))) 90 91 /* 92 * Arguments are as for qsort. 93 */ 94 int 95 mergesort(void *base, size_t nmemb, size_t size, 96 int (*cmp)(const void *, const void *)) 97 { 98 size_t i; 99 int sense; 100 int big, iflag; 101 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 102 u_char *list2, *list1, *p2, *p, *last, **p1; 103 104 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 105 errno = EINVAL; 106 return (-1); 107 } 108 109 if (nmemb == 0) 110 return (0); 111 112 /* 113 * XXX 114 * Stupid subtraction for the Cray. 115 */ 116 iflag = 0; 117 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 118 iflag = 1; 119 120 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 121 return (-1); 122 123 list1 = base; 124 setup(list1, list2, nmemb, size, cmp); 125 last = list2 + nmemb * size; 126 i = big = 0; 127 while (*EVAL(list2) != last) { 128 l2 = list1; 129 p1 = EVAL(list1); 130 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 131 p2 = *EVAL(p2); 132 f1 = l2; 133 f2 = l1 = list1 + (p2 - list2); 134 if (p2 != last) 135 p2 = *EVAL(p2); 136 l2 = list1 + (p2 - list2); 137 while (f1 < l1 && f2 < l2) { 138 if ((*cmp)(f1, f2) <= 0) { 139 q = f2; 140 b = f1, t = l1; 141 sense = -1; 142 } else { 143 q = f1; 144 b = f2, t = l2; 145 sense = 0; 146 } 147 if (!big) { /* here i = 0 */ 148 while ((b += size) < t && cmp(q, b) >sense) 149 if (++i == 6) { 150 big = 1; 151 goto EXPONENTIAL; 152 } 153 } else { 154 EXPONENTIAL: for (i = size; ; i <<= 1) 155 if ((p = (b + i)) >= t) { 156 if ((p = t - size) > b && 157 (*cmp)(q, p) <= sense) 158 t = p; 159 else 160 b = p; 161 break; 162 } else if ((*cmp)(q, p) <= sense) { 163 t = p; 164 if (i == size) 165 big = 0; 166 goto FASTCASE; 167 } else 168 b = p; 169 while (t > b+size) { 170 i = (((t - b) / size) >> 1) * size; 171 if ((*cmp)(q, p = b + i) <= sense) 172 t = p; 173 else 174 b = p; 175 } 176 goto COPY; 177 FASTCASE: while (i > size) 178 if ((*cmp)(q, 179 p = b + (i >>= 1)) <= sense) 180 t = p; 181 else 182 b = p; 183 COPY: b = t; 184 } 185 i = size; 186 if (q == f1) { 187 if (iflag) { 188 ICOPY_LIST(f2, tp2, b); 189 ICOPY_ELT(f1, tp2, i); 190 } else { 191 CCOPY_LIST(f2, tp2, b); 192 CCOPY_ELT(f1, tp2, i); 193 } 194 } else { 195 if (iflag) { 196 ICOPY_LIST(f1, tp2, b); 197 ICOPY_ELT(f2, tp2, i); 198 } else { 199 CCOPY_LIST(f1, tp2, b); 200 CCOPY_ELT(f2, tp2, i); 201 } 202 } 203 } 204 if (f2 < l2) { 205 if (iflag) 206 ICOPY_LIST(f2, tp2, l2); 207 else 208 CCOPY_LIST(f2, tp2, l2); 209 } else if (f1 < l1) { 210 if (iflag) 211 ICOPY_LIST(f1, tp2, l1); 212 else 213 CCOPY_LIST(f1, tp2, l1); 214 } 215 *p1 = l2; 216 } 217 tp2 = list1; /* swap list1, list2 */ 218 list1 = list2; 219 list2 = tp2; 220 last = list2 + nmemb*size; 221 } 222 if (base == list2) { 223 memmove(list2, list1, nmemb*size); 224 list2 = list1; 225 } 226 free(list2); 227 return (0); 228 } 229 230 #define swap(a, b) { \ 231 s = b; \ 232 i = size; \ 233 do { \ 234 tmp = *a; *a++ = *s; *s++ = tmp; \ 235 } while (--i); \ 236 a -= size; \ 237 } 238 #define reverse(bot, top) { \ 239 s = top; \ 240 do { \ 241 i = size; \ 242 do { \ 243 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 244 } while (--i); \ 245 s -= size2; \ 246 } while(bot < s); \ 247 } 248 249 /* 250 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 251 * increasing order, list2 in a corresponding linked list. Checks for runs 252 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 253 * is defined. Otherwise simple pairwise merging is used.) 254 */ 255 static void 256 setup(u_char *list1, u_char *list2, size_t n, size_t size, 257 int (*cmp)(const void *, const void *)) 258 { 259 int i, length, size2, tmp, sense; 260 u_char *f1, *f2, *s, *l2, *last, *p2; 261 262 size2 = size*2; 263 if (n <= 5) { 264 insertionsort(list1, n, size, cmp); 265 *EVAL(list2) = (u_char*) list2 + n*size; 266 return; 267 } 268 /* 269 * Avoid running pointers out of bounds; limit n to evens 270 * for simplicity. 271 */ 272 i = 4 + (n & 1); 273 insertionsort(list1 + (n - i) * size, i, size, cmp); 274 last = list1 + size * (n - i); 275 *EVAL(list2 + (last - list1)) = list2 + n * size; 276 277 #ifdef NATURAL 278 p2 = list2; 279 f1 = list1; 280 sense = (cmp(f1, f1 + size) > 0); 281 for (; f1 < last; sense = !sense) { 282 length = 2; 283 /* Find pairs with same sense. */ 284 for (f2 = f1 + size2; f2 < last; f2 += size2) { 285 if ((cmp(f2, f2+ size) > 0) != sense) 286 break; 287 length += 2; 288 } 289 if (length < THRESHOLD) { /* Pairwise merge */ 290 do { 291 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 292 if (sense > 0) 293 swap (f1, f1 + size); 294 } while ((f1 += size2) < f2); 295 } else { /* Natural merge */ 296 l2 = f2; 297 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 298 if ((cmp(f2-size, f2) > 0) != sense) { 299 p2 = *EVAL(p2) = f2 - list1 + list2; 300 if (sense > 0) 301 reverse(f1, f2-size); 302 f1 = f2; 303 } 304 } 305 if (sense > 0) 306 reverse (f1, f2-size); 307 f1 = f2; 308 if (f2 < last || cmp(f2 - size, f2) > 0) 309 p2 = *EVAL(p2) = f2 - list1 + list2; 310 else 311 p2 = *EVAL(p2) = list2 + n*size; 312 } 313 } 314 #else /* pairwise merge only. */ 315 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 316 p2 = *EVAL(p2) = p2 + size2; 317 if (cmp (f1, f1 + size) > 0) 318 swap(f1, f1 + size); 319 } 320 #endif /* NATURAL */ 321 } 322 323 /* 324 * This is to avoid out-of-bounds addresses in sorting the 325 * last 4 elements. 326 */ 327 static void 328 insertionsort(u_char *a, size_t n, size_t size, 329 int (*cmp)(const void *, const void *)) 330 { 331 u_char *ai, *s, *t, *u, tmp; 332 int i; 333 334 for (ai = a+size; --n >= 1; ai += size) 335 for (t = ai; t > a; t -= size) { 336 u = t - size; 337 if (cmp(u, t) <= 0) 338 break; 339 swap(u, t); 340 } 341 } 342