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. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)merge.c  8.2 (Berkeley) 2/14/94
  37  * $DragonFly: src/lib/libc/stdlib/merge.c,v 1.6 2005/11/20 12:37:48 swildner Exp $
  38  */
  39
  40 /*
  41  * Hybrid exponential search/linear search merge sort with hybrid
  42  * natural/pairwise first pass.  Requires about .3% more comparisons
  43  * for random data than LSMS with pairwise first pass alone.
  44  * It works for objects as small as two bytes.
  45  */
  46
  47 #define NATURAL
  48 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
  49
  50 /* #define NATURAL to get hybrid natural merge.
  51  * (The default is pairwise merging.)
  52  */
  53
  54 #include <sys/types.h>
  55
  56 #include <errno.h>
  57 #include <stdlib.h>
  58 #include <string.h>
  59
  60 static void setup(u_char *, u_char *, size_t, size_t,
  61     int (*)(const void *, const void *));
  62 static void insertionsort(u_char *, size_t, size_t,
  63     int (*)(const void *, const void *));
  64
  65 #define ISIZE sizeof(int)
  66 #define PSIZE sizeof(u_char *)
  67 #define ICOPY_LIST(src, dst, last)                              \
  68         do                                                      \
  69         *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;    \
  70         while(src < last)
  71 #define ICOPY_ELT(src, dst, i)                                  \
  72         do                                                      \
  73         *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;  \
  74         while (i -= ISIZE)
  75
  76 #define CCOPY_LIST(src, dst, last)              \
  77         do                                      \
  78                 *dst++ = *src++;                \
  79         while (src < last)
  80 #define CCOPY_ELT(src, dst, i)                  \
  81         do                                      \
  82                 *dst++ = *src++;                \
  83         while (i -= 1)
  84
  85 /*
  86  * Find the next possible pointer head.  (Trickery for forcing an array
  87  * to do double duty as a linked list when objects do not align with word
  88  * boundaries.
  89  */
  90 /* Assumption: PSIZE is a power of 2. */
  91 #define EVAL(p) (u_char **)                                             \
  92         ((u_char *)0 +                                                  \
  93             (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
  94
  95 /*
  96  * Arguments are as for qsort.
  97  */
  98 int
  99 mergesort(void *base, size_t nmemb, size_t size,
 100           int (*cmp)(const void *, const void *))
 101 {
 102         size_t i;
 103         int  sense;
 104         int big, iflag;
 105         u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 106         u_char *list2, *list1, *p2, *p, *last, **p1;
 107
 108         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
 109                 errno = EINVAL;
 110                 return (-1);
 111         }
 112
 113         if (nmemb == 0)
 114                 return (0);
 115
 116         /*
 117          * XXX
 118          * Stupid subtraction for the Cray.
 119          */
 120         iflag = 0;
 121         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
 122                 iflag = 1;
 123
 124         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
 125                 return (-1);
 126
 127         list1 = base;
 128         setup(list1, list2, nmemb, size, cmp);
 129         last = list2 + nmemb * size;
 130         i = big = 0;
 131         while (*EVAL(list2) != last) {
 132             l2 = list1;
 133             p1 = EVAL(list1);
 134             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
 135                 p2 = *EVAL(p2);
 136                 f1 = l2;
 137                 f2 = l1 = list1 + (p2 - list2);
 138                 if (p2 != last)
 139                         p2 = *EVAL(p2);
 140                 l2 = list1 + (p2 - list2);
 141                 while (f1 < l1 && f2 < l2) {
 142                         if ((*cmp)(f1, f2) <= 0) {
 143                                 q = f2;
 144                                 b = f1, t = l1;
 145                                 sense = -1;
 146                         } else {
 147                                 q = f1;
 148                                 b = f2, t = l2;
 149                                 sense = 0;
 150                         }
 151                         if (!big) {     /* here i = 0 */
 152                                 while ((b += size) < t && cmp(q, b) >sense)
 153                                         if (++i == 6) {
 154                                                 big = 1;
 155                                                 goto EXPONENTIAL;
 156                                         }
 157                         } else {
 158 EXPONENTIAL:                    for (i = size; ; i <<= 1)
 159                                         if ((p = (b + i)) >= t) {
 160                                                 if ((p = t - size) > b &&
 161                                                     (*cmp)(q, p) <= sense)
 162                                                         t = p;
 163                                                 else
 164                                                         b = p;
 165                                                 break;
 166                                         } else if ((*cmp)(q, p) <= sense) {
 167                                                 t = p;
 168                                                 if (i == size)
 169                                                         big = 0;
 170                                                 goto FASTCASE;
 171                                         } else
 172                                                 b = p;
 173                                 while (t > b+size) {
 174                                         i = (((t - b) / size) >> 1) * size;
 175                                         if ((*cmp)(q, p = b + i) <= sense)
 176                                                 t = p;
 177                                         else
 178                                                 b = p;
 179                                 }
 180                                 goto COPY;
 181 FASTCASE:                       while (i > size)
 182                                         if ((*cmp)(q,
 183                                                 p = b + (i >>= 1)) <= sense)
 184                                                 t = p;
 185                                         else
 186                                                 b = p;
 187 COPY:                           b = t;
 188                         }
 189                         i = size;
 190                         if (q == f1) {
 191                                 if (iflag) {
 192                                         ICOPY_LIST(f2, tp2, b);
 193                                         ICOPY_ELT(f1, tp2, i);
 194                                 } else {
 195                                         CCOPY_LIST(f2, tp2, b);
 196                                         CCOPY_ELT(f1, tp2, i);
 197                                 }
 198                         } else {
 199                                 if (iflag) {
 200                                         ICOPY_LIST(f1, tp2, b);
 201                                         ICOPY_ELT(f2, tp2, i);
 202                                 } else {
 203                                         CCOPY_LIST(f1, tp2, b);
 204                                         CCOPY_ELT(f2, tp2, i);
 205                                 }
 206                         }
 207                 }
 208                 if (f2 < l2) {
 209                         if (iflag)
 210                                 ICOPY_LIST(f2, tp2, l2);
 211                         else
 212                                 CCOPY_LIST(f2, tp2, l2);
 213                 } else if (f1 < l1) {
 214                         if (iflag)
 215                                 ICOPY_LIST(f1, tp2, l1);
 216                         else
 217                                 CCOPY_LIST(f1, tp2, l1);
 218                 }
 219                 *p1 = l2;
 220             }
 221             tp2 = list1;        /* swap list1, list2 */
 222             list1 = list2;
 223             list2 = tp2;
 224             last = list2 + nmemb*size;
 225         }
 226         if (base == list2) {
 227                 memmove(list2, list1, nmemb*size);
 228                 list2 = list1;
 229         }
 230         free(list2);
 231         return (0);
 232 }
 233
 234 #define swap(a, b) {                                    \
 235                 s = b;                                  \
 236                 i = size;                               \
 237                 do {                                    \
 238                         tmp = *a; *a++ = *s; *s++ = tmp; \
 239                 } while (--i);                          \
 240                 a -= size;                              \
 241         }
 242 #define reverse(bot, top) {                             \
 243         s = top;                                        \
 244         do {                                            \
 245                 i = size;                               \
 246                 do {                                    \
 247                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 248                 } while (--i);                          \
 249                 s -= size2;                             \
 250         } while(bot < s);                               \
 251 }
 252
 253 /*
 254  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 255  * increasing order, list2 in a corresponding linked list.  Checks for runs
 256  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 257  * is defined.  Otherwise simple pairwise merging is used.)
 258  */
 259 void
 260 setup(u_char *list1, u_char *list2, size_t n, size_t size,
 261       int (*cmp)(const void *, const void *))
 262 {
 263         int i, length, size2, tmp, sense;
 264         u_char *f1, *f2, *s, *l2, *last, *p2;
 265
 266         size2 = size*2;
 267         if (n <= 5) {
 268                 insertionsort(list1, n, size, cmp);
 269                 *EVAL(list2) = (u_char*) list2 + n*size;
 270                 return;
 271         }
 272         /*
 273          * Avoid running pointers out of bounds; limit n to evens
 274          * for simplicity.
 275          */
 276         i = 4 + (n & 1);
 277         insertionsort(list1 + (n - i) * size, i, size, cmp);
 278         last = list1 + size * (n - i);
 279         *EVAL(list2 + (last - list1)) = list2 + n * size;
 280
 281 #ifdef NATURAL
 282         p2 = list2;
 283         f1 = list1;
 284         sense = (cmp(f1, f1 + size) > 0);
 285         for (; f1 < last; sense = !sense) {
 286                 length = 2;
 287                                         /* Find pairs with same sense. */
 288                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 289                         if ((cmp(f2, f2+ size) > 0) != sense)
 290                                 break;
 291                         length += 2;
 292                 }
 293                 if (length < THRESHOLD) {               /* Pairwise merge */
 294                         do {
 295                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 296                                 if (sense > 0)
 297                                         swap (f1, f1 + size);
 298                         } while ((f1 += size2) < f2);
 299                 } else {                                /* Natural merge */
 300                         l2 = f2;
 301                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 302                                 if ((cmp(f2-size, f2) > 0) != sense) {
 303                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 304                                         if (sense > 0)
 305                                                 reverse(f1, f2-size);
 306                                         f1 = f2;
 307                                 }
 308                         }
 309                         if (sense > 0)
 310                                 reverse (f1, f2-size);
 311                         f1 = f2;
 312                         if (f2 < last || cmp(f2 - size, f2) > 0)
 313                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 314                         else
 315                                 p2 = *EVAL(p2) = list2 + n*size;
 316                 }
 317         }
 318 #else           /* pairwise merge only. */
 319         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 320                 p2 = *EVAL(p2) = p2 + size2;
 321                 if (cmp (f1, f1 + size) > 0)
 322                         swap(f1, f1 + size);
 323         }
 324 #endif /* NATURAL */
 325 }
 326
 327 /*
 328  * This is to avoid out-of-bounds addresses in sorting the
 329  * last 4 elements.
 330  */
 331 static void
 332 insertionsort(u_char *a, size_t n, size_t size,
 333               int (*cmp)(const void *, const void *))
 334 {
 335         u_char *ai, *s, *t, *u, tmp;
 336         int i;
 337
 338         for (ai = a+size; --n >= 1; ai += size)
 339                 for (t = ai; t > a; t -= size) {
 340                         u = t - size;
 341                         if (cmp(u, t) <= 0)
 342                                 break;
 343                         swap(u, t);
 344                 }
 345 }