lib/libc/stdlib/merge.c

   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  * $DragonFly: src/lib/libc/stdlib/merge.c,v 1.6 2005/11/20 12:37:48 swildner Exp $
  35  */
  36
  37 /*
  38  * Hybrid exponential search/linear search merge sort with hybrid
  39  * natural/pairwise first pass.  Requires about .3% more comparisons
  40  * for random data than LSMS with pairwise first pass alone.
  41  * It works for objects as small as two bytes.
  42  */
  43
  44 #define NATURAL
  45 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
  46
  47 /* #define NATURAL to get hybrid natural merge.
  48  * (The default is pairwise merging.)
  49  */
  50
  51 #include <sys/types.h>
  52
  53 #include <errno.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56
  57 static void setup(u_char *, u_char *, size_t, size_t,
  58     int (*)(const void *, const void *));
  59 static void insertionsort(u_char *, size_t, size_t,
  60     int (*)(const void *, const void *));
  61
  62 #define ISIZE sizeof(int)
  63 #define PSIZE sizeof(u_char *)
  64 #define ICOPY_LIST(src, dst, last)                              \
  65         do                                                      \
  66         *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;    \
  67         while(src < last)
  68 #define ICOPY_ELT(src, dst, i)                                  \
  69         do                                                      \
  70         *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;  \
  71         while (i -= ISIZE)
  72
  73 #define CCOPY_LIST(src, dst, last)              \
  74         do                                      \
  75                 *dst++ = *src++;                \
  76         while (src < last)
  77 #define CCOPY_ELT(src, dst, i)                  \
  78         do                                      \
  79                 *dst++ = *src++;                \
  80         while (i -= 1)
  81
  82 /*
  83  * Find the next possible pointer head.  (Trickery for forcing an array
  84  * to do double duty as a linked list when objects do not align with word
  85  * boundaries.
  86  */
  87 /* Assumption: PSIZE is a power of 2. */
  88 #define EVAL(p) (u_char **)                                             \
  89         ((u_char *)0 +                                                  \
  90             (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
  91
  92 /*
  93  * Arguments are as for qsort.
  94  */
  95 int
  96 mergesort(void *base, size_t nmemb, size_t size,
  97           int (*cmp)(const void *, const void *))
  98 {
  99         size_t i;
 100         int sense;
 101         int big, iflag;
 102         u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 103         u_char *list2, *list1, *p2, *p, *last, **p1;
 104
 105         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
 106                 errno = EINVAL;
 107                 return (-1);
 108         }
 109
 110         if (nmemb == 0)
 111                 return (0);
 112
 113         /*
 114          * XXX
 115          * Stupid subtraction for the Cray.
 116          */
 117         iflag = 0;
 118         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
 119                 iflag = 1;
 120
 121         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
 122                 return (-1);
 123
 124         list1 = base;
 125         setup(list1, list2, nmemb, size, cmp);
 126         last = list2 + nmemb * size;
 127         i = big = 0;
 128         while (*EVAL(list2) != last) {
 129             l2 = list1;
 130             p1 = EVAL(list1);
 131             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
 132                 p2 = *EVAL(p2);
 133                 f1 = l2;
 134                 f2 = l1 = list1 + (p2 - list2);
 135                 if (p2 != last)
 136                         p2 = *EVAL(p2);
 137                 l2 = list1 + (p2 - list2);
 138                 while (f1 < l1 && f2 < l2) {
 139                         if ((*cmp)(f1, f2) <= 0) {
 140                                 q = f2;
 141                                 b = f1, t = l1;
 142                                 sense = -1;
 143                         } else {
 144                                 q = f1;
 145                                 b = f2, t = l2;
 146                                 sense = 0;
 147                         }
 148                         if (!big) {     /* here i = 0 */
 149                                 while ((b += size) < t && cmp(q, b) >sense)
 150                                         if (++i == 6) {
 151                                                 big = 1;
 152                                                 goto EXPONENTIAL;
 153                                         }
 154                         } else {
 155 EXPONENTIAL:                    for (i = size; ; i <<= 1)
 156                                         if ((p = (b + i)) >= t) {
 157                                                 if ((p = t - size) > b &&
 158                                                     (*cmp)(q, p) <= sense)
 159                                                         t = p;
 160                                                 else
 161                                                         b = p;
 162                                                 break;
 163                                         } else if ((*cmp)(q, p) <= sense) {
 164                                                 t = p;
 165                                                 if (i == size)
 166                                                         big = 0;
 167                                                 goto FASTCASE;
 168                                         } else
 169                                                 b = p;
 170                                 while (t > b+size) {
 171                                         i = (((t - b) / size) >> 1) * size;
 172                                         if ((*cmp)(q, p = b + i) <= sense)
 173                                                 t = p;
 174                                         else
 175                                                 b = p;
 176                                 }
 177                                 goto COPY;
 178 FASTCASE:                       while (i > size)
 179                                         if ((*cmp)(q,
 180                                                 p = b + (i >>= 1)) <= sense)
 181                                                 t = p;
 182                                         else
 183                                                 b = p;
 184 COPY:                           b = t;
 185                         }
 186                         i = size;
 187                         if (q == f1) {
 188                                 if (iflag) {
 189                                         ICOPY_LIST(f2, tp2, b);
 190                                         ICOPY_ELT(f1, tp2, i);
 191                                 } else {
 192                                         CCOPY_LIST(f2, tp2, b);
 193                                         CCOPY_ELT(f1, tp2, i);
 194                                 }
 195                         } else {
 196                                 if (iflag) {
 197                                         ICOPY_LIST(f1, tp2, b);
 198                                         ICOPY_ELT(f2, tp2, i);
 199                                 } else {
 200                                         CCOPY_LIST(f1, tp2, b);
 201                                         CCOPY_ELT(f2, tp2, i);
 202                                 }
 203                         }
 204                 }
 205                 if (f2 < l2) {
 206                         if (iflag)
 207                                 ICOPY_LIST(f2, tp2, l2);
 208                         else
 209                                 CCOPY_LIST(f2, tp2, l2);
 210                 } else if (f1 < l1) {
 211                         if (iflag)
 212                                 ICOPY_LIST(f1, tp2, l1);
 213                         else
 214                                 CCOPY_LIST(f1, tp2, l1);
 215                 }
 216                 *p1 = l2;
 217             }
 218             tp2 = list1;        /* swap list1, list2 */
 219             list1 = list2;
 220             list2 = tp2;
 221             last = list2 + nmemb*size;
 222         }
 223         if (base == list2) {
 224                 memmove(list2, list1, nmemb*size);
 225                 list2 = list1;
 226         }
 227         free(list2);
 228         return (0);
 229 }
 230
 231 #define swap(a, b) {                                    \
 232                 s = b;                                  \
 233                 i = size;                               \
 234                 do {                                    \
 235                         tmp = *a; *a++ = *s; *s++ = tmp; \
 236                 } while (--i);                          \
 237                 a -= size;                              \
 238         }
 239 #define reverse(bot, top) {                             \
 240         s = top;                                        \
 241         do {                                            \
 242                 i = size;                               \
 243                 do {                                    \
 244                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 245                 } while (--i);                          \
 246                 s -= size2;                             \
 247         } while(bot < s);                               \
 248 }
 249
 250 /*
 251  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 252  * increasing order, list2 in a corresponding linked list.  Checks for runs
 253  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 254  * is defined.  Otherwise simple pairwise merging is used.)
 255  */
 256 static void
 257 setup(u_char *list1, u_char *list2, size_t n, size_t size,
 258       int (*cmp)(const void *, const void *))
 259 {
 260         int i, length, size2, tmp, sense;
 261         u_char *f1, *f2, *s, *l2, *last, *p2;
 262
 263         size2 = size*2;
 264         if (n <= 5) {
 265                 insertionsort(list1, n, size, cmp);
 266                 *EVAL(list2) = (u_char*) list2 + n*size;
 267                 return;
 268         }
 269         /*
 270          * Avoid running pointers out of bounds; limit n to evens
 271          * for simplicity.
 272          */
 273         i = 4 + (n & 1);
 274         insertionsort(list1 + (n - i) * size, i, size, cmp);
 275         last = list1 + size * (n - i);
 276         *EVAL(list2 + (last - list1)) = list2 + n * size;
 277
 278 #ifdef NATURAL
 279         p2 = list2;
 280         f1 = list1;
 281         sense = (cmp(f1, f1 + size) > 0);
 282         for (; f1 < last; sense = !sense) {
 283                 length = 2;
 284                                         /* Find pairs with same sense. */
 285                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 286                         if ((cmp(f2, f2+ size) > 0) != sense)
 287                                 break;
 288                         length += 2;
 289                 }
 290                 if (length < THRESHOLD) {               /* Pairwise merge */
 291                         do {
 292                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 293                                 if (sense > 0)
 294                                         swap (f1, f1 + size);
 295                         } while ((f1 += size2) < f2);
 296                 } else {                                /* Natural merge */
 297                         l2 = f2;
 298                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 299                                 if ((cmp(f2-size, f2) > 0) != sense) {
 300                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 301                                         if (sense > 0)
 302                                                 reverse(f1, f2-size);
 303                                         f1 = f2;
 304                                 }
 305                         }
 306                         if (sense > 0)
 307                                 reverse (f1, f2-size);
 308                         f1 = f2;
 309                         if (f2 < last || cmp(f2 - size, f2) > 0)
 310                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 311                         else
 312                                 p2 = *EVAL(p2) = list2 + n*size;
 313                 }
 314         }
 315 #else           /* pairwise merge only. */
 316         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 317                 p2 = *EVAL(p2) = p2 + size2;
 318                 if (cmp (f1, f1 + size) > 0)
 319                         swap(f1, f1 + size);
 320         }
 321 #endif /* NATURAL */
 322 }
 323
 324 /*
 325  * This is to avoid out-of-bounds addresses in sorting the
 326  * last 4 elements.
 327  */
 328 static void
 329 insertionsort(u_char *a, size_t n, size_t size,
 330               int (*cmp)(const void *, const void *))
 331 {
 332         u_char *ai, *s, *t, *u, tmp;
 333         int i;
 334
 335         for (ai = a+size; --n >= 1; ai += size)
 336                 for (t = ai; t > a; t -= size) {
 337                         u = t - size;
 338                         if (cmp(u, t) <= 0)
 339                                 break;
 340                         swap(u, t);
 341                 }
 342 }