lib/libc/stdlib/merge.c

   1 /*      $NetBSD: merge.c,v 1.14 2012/03/13 21:13:48 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. 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 1.14 2012/03/13 21:13:48 christos 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(u_char *, u_char *, size_t, size_t,
  71     int (*)(const void *, const void *));
  72 static void insertionsort(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(void *base, size_t nmemb, size_t size,
 112     int (*cmp)(const void *, const void *))
 113 {
 114         size_t i;
 115         int sense;
 116         int big, iflag;
 117         u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 118         u_char *list2, *list1, *p2, *p, *last, **p1;
 119
 120         _DIAGASSERT(base != NULL);
 121         _DIAGASSERT(cmp != NULL);
 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 +
 202                                                     (i = (unsigned int) i >> 1)) <= sense)
 203                                                 t = p;
 204                                         else
 205                                                 b = p;
 206 COPY:                           b = t;
 207                         }
 208                         i = size;
 209                         if (q == f1) {
 210                                 if (iflag) {
 211                                         ICOPY_LIST(f2, tp2, b);
 212                                         ICOPY_ELT(f1, tp2, i);
 213                                 } else {
 214                                         CCOPY_LIST(f2, tp2, b);
 215                                         CCOPY_ELT(f1, tp2, i);
 216                                 }
 217                         } else {
 218                                 if (iflag) {
 219                                         ICOPY_LIST(f1, tp2, b);
 220                                         ICOPY_ELT(f2, tp2, i);
 221                                 } else {
 222                                         CCOPY_LIST(f1, tp2, b);
 223                                         CCOPY_ELT(f2, tp2, i);
 224                                 }
 225                         }
 226                 }
 227                 if (f2 < l2) {
 228                         if (iflag)
 229                                 ICOPY_LIST(f2, tp2, l2);
 230                         else
 231                                 CCOPY_LIST(f2, tp2, l2);
 232                 } else if (f1 < l1) {
 233                         if (iflag)
 234                                 ICOPY_LIST(f1, tp2, l1);
 235                         else
 236                                 CCOPY_LIST(f1, tp2, l1);
 237                 }
 238                 *p1 = l2;
 239             }
 240             tp2 = list1;        /* swap list1, list2 */
 241             list1 = list2;
 242             list2 = tp2;
 243             last = list2 + nmemb*size;
 244         }
 245         if (base == list2) {
 246                 memmove(list2, list1, nmemb*size);
 247                 list2 = list1;
 248         }
 249         free(list2);
 250         return (0);
 251 }
 252
 253 #define swap(a, b) {                                    \
 254                 s = b;                                  \
 255                 i = size;                               \
 256                 do {                                    \
 257                         tmp = *a; *a++ = *s; *s++ = tmp; \
 258                 } while (--i);                          \
 259                 a -= size;                              \
 260         }
 261 #define reverse(bot, top) {                             \
 262         s = top;                                        \
 263         do {                                            \
 264                 i = size;                               \
 265                 do {                                    \
 266                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 267                 } while (--i);                          \
 268                 s -= size2;                             \
 269         } while(bot < s);                               \
 270 }
 271
 272 /*
 273  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 274  * increasing order, list2 in a corresponding linked list.  Checks for runs
 275  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 276  * is defined.  Otherwise simple pairwise merging is used.)
 277  */
 278
 279 /* XXX: shouldn't this function be static? - lukem 990810 */
 280 void
 281 setup(u_char *list1, u_char *list2, size_t n, size_t size,
 282     int (*cmp)(const void *, const void *))
 283 {
 284         int length, tmp, sense;
 285         u_char *f1, *f2, *s, *l2, *last, *p2;
 286         size_t size2, i;
 287
 288         _DIAGASSERT(cmp != NULL);
 289         _DIAGASSERT(list1 != NULL);
 290         _DIAGASSERT(list2 != NULL);
 291
 292         size2 = size*2;
 293         if (n <= 5) {
 294                 insertionsort(list1, n, size, cmp);
 295                 *EVAL(list2) = list2 + n*size;
 296                 return;
 297         }
 298         /*
 299          * Avoid running pointers out of bounds; limit n to evens
 300          * for simplicity.
 301          */
 302         i = 4 + (n & 1);
 303         insertionsort(list1 + (n - i) * size, i, size, cmp);
 304         last = list1 + size * (n - i);
 305         *EVAL(list2 + (last - list1)) = list2 + n * size;
 306
 307 #ifdef NATURAL
 308         p2 = list2;
 309         f1 = list1;
 310         sense = (cmp(f1, f1 + size) > 0);
 311         for (; f1 < last; sense = !sense) {
 312                 length = 2;
 313                                         /* Find pairs with same sense. */
 314                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 315                         if ((cmp(f2, f2+ size) > 0) != sense)
 316                                 break;
 317                         length += 2;
 318                 }
 319                 if (length < THRESHOLD) {               /* Pairwise merge */
 320                         do {
 321                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 322                                 if (sense > 0)
 323                                         swap (f1, f1 + size);
 324                         } while ((f1 += size2) < f2);
 325                 } else {                                /* Natural merge */
 326                         l2 = f2;
 327                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 328                                 if ((cmp(f2-size, f2) > 0) != sense) {
 329                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 330                                         if (sense > 0)
 331                                                 reverse(f1, f2 - size);
 332                                         f1 = f2;
 333                                 }
 334                         }
 335                         if (sense > 0)
 336                                 reverse(f1, f2 - size);
 337                         f1 = f2;
 338                         if (f2 < last || cmp(f2 - size, f2) > 0)
 339                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 340                         else
 341                                 p2 = *EVAL(p2) = list2 + n*size;
 342                 }
 343         }
 344 #else           /* pairwise merge only. */
 345         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 346                 p2 = *EVAL(p2) = p2 + size2;
 347                 if (cmp (f1, f1 + size) > 0)
 348                         swap(f1, f1 + size);
 349         }
 350 #endif /* NATURAL */
 351 }
 352
 353 /*
 354  * This is to avoid out-of-bounds addresses in sorting the
 355  * last 4 elements.
 356  */
 357 static void
 358 insertionsort(u_char *a, size_t n, size_t size,
 359     int (*cmp)(const void *, const void *))
 360 {
 361         u_char *ai, *s, *t, *u, tmp;
 362         size_t i;
 363
 364         _DIAGASSERT(a != NULL);
 365         _DIAGASSERT(cmp != NULL);
 366
 367         for (ai = a+size; --n >= 1; ai += size)
 368                 for (t = ai; t > a; t -= size) {
 369                         u = t - size;
 370                         if (cmp(u, t) <= 0)
 371                                 break;
 372                         swap(u, t);
 373                 }
 374 }