compat/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  * 4. 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
  33 #include <sys/cdefs.h>
  34
  35 /*
  36  * Hybrid exponential search/linear search merge sort with hybrid
  37  * natural/pairwise first pass.  Requires about .3% more comparisons
  38  * for random data than LSMS with pairwise first pass alone.
  39  * It works for objects as small as two bytes.
  40  */
  41
  42 #define NATURAL
  43 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
  44
  45 /* #define NATURAL to get hybrid natural merge.
  46  * (The default is pairwise merging.)
  47  */
  48
  49 #include <sys/types.h>
  50
  51 #include <errno.h>
  52 #include <stdlib.h>
  53 #include <string.h>
  54
  55 #include "got_compat.h"
  56
  57 static void setup(unsigned char *, unsigned char *, size_t, size_t,
  58     int (*)(const void *, const void *));
  59 static void insertionsort(unsigned char *, size_t, size_t,
  60     int (*)(const void *, const void *));
  61
  62 #define ISIZE sizeof(int)
  63 #define PSIZE sizeof(unsigned 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) (unsigned char **)                                      \
  89         ((unsigned char *)0 +                                           \
  90          (((unsigned char *)p + PSIZE - 1 -                             \
  91            (unsigned char *)0) & ~(PSIZE - 1)))
  92
  93 /*
  94  * Arguments are as for qsort.
  95  */
  96 int
  97 mergesort(void *base, size_t nmemb, size_t size,
  98         int (*cmp)(const void *, const void *))
  99 {
 100         size_t i;
 101         int sense;
 102         int big, iflag;
 103         unsigned char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 104         unsigned char *list2, *list1, *p2, *p, *last, **p1;
 105
 106         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
 107                 errno = EINVAL;
 108                 return (-1);
 109         }
 110
 111         if (nmemb == 0)
 112                 return (0);
 113
 114         /*
 115          * XXX
 116          * Stupid subtraction for the Cray.
 117          */
 118         iflag = 0;
 119         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
 120                 iflag = 1;
 121
 122         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
 123                 return (-1);
 124
 125         list1 = base;
 126         setup(list1, list2, nmemb, size, cmp);
 127         last = list2 + nmemb * size;
 128         i = big = 0;
 129         while (*EVAL(list2) != last) {
 130             l2 = list1;
 131             p1 = EVAL(list1);
 132             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
 133                 p2 = *EVAL(p2);
 134                 f1 = l2;
 135                 f2 = l1 = list1 + (p2 - list2);
 136                 if (p2 != last)
 137                         p2 = *EVAL(p2);
 138                 l2 = list1 + (p2 - list2);
 139                 while (f1 < l1 && f2 < l2) {
 140                         if ((*cmp)(f1, f2) <= 0) {
 141                                 q = f2;
 142                                 b = f1, t = l1;
 143                                 sense = -1;
 144                         } else {
 145                                 q = f1;
 146                                 b = f2, t = l2;
 147                                 sense = 0;
 148                         }
 149                         if (!big) {     /* here i = 0 */
 150                                 while ((b += size) < t && cmp(q, b) >sense)
 151                                         if (++i == 6) {
 152                                                 big = 1;
 153                                                 goto EXPONENTIAL;
 154                                         }
 155                         } else {
 156 EXPONENTIAL:                    for (i = size; ; i <<= 1)
 157                                         if ((p = (b + i)) >= t) {
 158                                                 if ((p = t - size) > b &&
 159                                                     (*cmp)(q, p) <= sense)
 160                                                         t = p;
 161                                                 else
 162                                                         b = p;
 163                                                 break;
 164                                         } else if ((*cmp)(q, p) <= sense) {
 165                                                 t = p;
 166                                                 if (i == size)
 167                                                         big = 0;
 168                                                 goto FASTCASE;
 169                                         } else
 170                                                 b = p;
 171                                 while (t > b+size) {
 172                                         i = (((t - b) / size) >> 1) * size;
 173                                         if ((*cmp)(q, p = b + i) <= sense)
 174                                                 t = p;
 175                                         else
 176                                                 b = p;
 177                                 }
 178                                 goto COPY;
 179 FASTCASE:                       while (i > size)
 180                                         if ((*cmp)(q,
 181                                                 p = b + (i >>= 1)) <= sense)
 182                                                 t = p;
 183                                         else
 184                                                 b = p;
 185 COPY:                           b = t;
 186                         }
 187                         i = size;
 188                         if (q == f1) {
 189                                 if (iflag) {
 190                                         ICOPY_LIST(f2, tp2, b);
 191                                         ICOPY_ELT(f1, tp2, i);
 192                                 } else {
 193                                         CCOPY_LIST(f2, tp2, b);
 194                                         CCOPY_ELT(f1, tp2, i);
 195                                 }
 196                         } else {
 197                                 if (iflag) {
 198                                         ICOPY_LIST(f1, tp2, b);
 199                                         ICOPY_ELT(f2, tp2, i);
 200                                 } else {
 201                                         CCOPY_LIST(f1, tp2, b);
 202                                         CCOPY_ELT(f2, tp2, i);
 203                                 }
 204                         }
 205                 }
 206                 if (f2 < l2) {
 207                         if (iflag)
 208                                 ICOPY_LIST(f2, tp2, l2);
 209                         else
 210                                 CCOPY_LIST(f2, tp2, l2);
 211                 } else if (f1 < l1) {
 212                         if (iflag)
 213                                 ICOPY_LIST(f1, tp2, l1);
 214                         else
 215                                 CCOPY_LIST(f1, tp2, l1);
 216                 }
 217                 *p1 = l2;
 218             }
 219             tp2 = list1;        /* swap list1, list2 */
 220             list1 = list2;
 221             list2 = tp2;
 222             last = list2 + nmemb*size;
 223         }
 224         if (base == list2) {
 225                 memmove(list2, list1, nmemb*size);
 226                 list2 = list1;
 227         }
 228         free(list2);
 229         return (0);
 230 }
 231
 232 #define swap(a, b) {                                    \
 233                 s = b;                                  \
 234                 i = size;                               \
 235                 do {                                    \
 236                         tmp = *a; *a++ = *s; *s++ = tmp; \
 237                 } while (--i);                          \
 238                 a -= size;                              \
 239         }
 240 #define reverse(bot, top) {                             \
 241         s = top;                                        \
 242         do {                                            \
 243                 i = size;                               \
 244                 do {                                    \
 245                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 246                 } while (--i);                          \
 247                 s -= size2;                             \
 248         } while(bot < s);                               \
 249 }
 250
 251 /*
 252  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 253  * increasing order, list2 in a corresponding linked list.  Checks for runs
 254  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 255  * is defined.  Otherwise simple pairwise merging is used.)
 256  */
 257 static void
 258 setup(unsigned char *list1, unsigned char *list2, size_t n, size_t size,
 259         int (*cmp)(const void *, const void *))
 260 {
 261         int i, length, size2, tmp, sense;
 262         unsigned char *f1, *f2, *s, *l2, *last, *p2;
 263
 264         size2 = size*2;
 265         if (n <= 5) {
 266                 insertionsort(list1, n, size, cmp);
 267                 *EVAL(list2) = (unsigned char*) list2 + n*size;
 268                 return;
 269         }
 270         /*
 271          * Avoid running pointers out of bounds; limit n to evens
 272          * for simplicity.
 273          */
 274         i = 4 + (n & 1);
 275         insertionsort(list1 + (n - i) * size, i, size, cmp);
 276         last = list1 + size * (n - i);
 277         *EVAL(list2 + (last - list1)) = list2 + n * size;
 278
 279 #ifdef NATURAL
 280         p2 = list2;
 281         f1 = list1;
 282         sense = (cmp(f1, f1 + size) > 0);
 283         for (; f1 < last; sense = !sense) {
 284                 length = 2;
 285                                         /* Find pairs with same sense. */
 286                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 287                         if ((cmp(f2, f2+ size) > 0) != sense)
 288                                 break;
 289                         length += 2;
 290                 }
 291                 if (length < THRESHOLD) {               /* Pairwise merge */
 292                         do {
 293                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 294                                 if (sense > 0)
 295                                         swap (f1, f1 + size);
 296                         } while ((f1 += size2) < f2);
 297                 } else {                                /* Natural merge */
 298                         l2 = f2;
 299                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 300                                 if ((cmp(f2-size, f2) > 0) != sense) {
 301                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 302                                         if (sense > 0)
 303                                                 reverse(f1, f2-size);
 304                                         f1 = f2;
 305                                 }
 306                         }
 307                         if (sense > 0)
 308                                 reverse (f1, f2-size);
 309                         f1 = f2;
 310                         if (f2 < last || cmp(f2 - size, f2) > 0)
 311                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 312                         else
 313                                 p2 = *EVAL(p2) = list2 + n*size;
 314                 }
 315         }
 316 #else           /* pairwise merge only. */
 317         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 318                 p2 = *EVAL(p2) = p2 + size2;
 319                 if (cmp (f1, f1 + size) > 0)
 320                         swap(f1, f1 + size);
 321         }
 322 #endif /* NATURAL */
 323 }
 324
 325 /*
 326  * This is to avoid out-of-bounds addresses in sorting the
 327  * last 4 elements.
 328  */
 329 static void
 330 insertionsort(unsigned char *a, size_t n, size_t size,
 331         int (*cmp)(const void *, const void *))
 332 {
 333         unsigned char *ai, *s, *t, *u, tmp;
 334         int i;
 335
 336         for (ai = a+size; --n >= 1; ai += size)
 337                 for (t = ai; t > a; t -= size) {
 338                         u = t - size;
 339                         if (cmp(u, t) <= 0)
 340                                 break;
 341                         swap(u, t);
 342                 }
 343 }