lib/libc/stdlib/merge.c

   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 }