stdlib/merge-fbsd.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 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)merge.c     8.2 (Berkeley) 2/14/94";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdlib/merge.c,v 1.8 2007/01/09 00:28:10 imp Exp $");
  38
  39 /*
  40  * Hybrid exponential search/linear search merge sort with hybrid
  41  * natural/pairwise first pass.  Requires about .3% more comparisons
  42  * for random data than LSMS with pairwise first pass alone.
  43  * It works for objects as small as two bytes.
  44  */
  45
  46 #define NATURAL
  47 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
  48
  49 /* #define NATURAL to get hybrid natural merge.
  50  * (The default is pairwise merging.)
  51  */
  52
  53 #include <sys/types.h>
  54
  55 #include <errno.h>
  56 #include <stdlib.h>
  57 #include <string.h>
  58
  59 static void setup(u_char *, u_char *, size_t, size_t,
  60     int (*)(const void *, const void *));
  61 static void insertionsort(u_char *, size_t, size_t,
  62     int (*)(const void *, const void *));
  63
  64 #define ISIZE sizeof(int)
  65 #define PSIZE sizeof(u_char *)
  66 #define ICOPY_LIST(src, dst, last)                              \
  67         do                                                      \
  68         *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;    \
  69         while(src < last)
  70 #define ICOPY_ELT(src, dst, i)                                  \
  71         do                                                      \
  72         *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;  \
  73         while (i -= ISIZE)
  74
  75 #define CCOPY_LIST(src, dst, last)              \
  76         do                                      \
  77                 *dst++ = *src++;                \
  78         while (src < last)
  79 #define CCOPY_ELT(src, dst, i)                  \
  80         do                                      \
  81                 *dst++ = *src++;                \
  82         while (i -= 1)
  83
  84 /*
  85  * Find the next possible pointer head.  (Trickery for forcing an array
  86  * to do double duty as a linked list when objects do not align with word
  87  * boundaries.
  88  */
  89 /* Assumption: PSIZE is a power of 2. */
  90 #define EVAL(p) (u_char **)                                             \
  91         ((u_char *)0 +                                                  \
  92             (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
  93
  94 /*
  95  * Arguments are as for qsort.
  96  */
  97 int
  98 mergesort(base, nmemb, size, cmp)
  99         void *base;
 100         size_t nmemb;
 101         size_t size;
 102         int (*cmp)(const void *, const void *);
 103 {
 104         size_t i;
 105         int sense;
 106         int big, iflag;
 107         u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 108         u_char *list2, *list1, *p2, *p, *last, **p1;
 109
 110         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
 111                 errno = EINVAL;
 112                 return (-1);
 113         }
 114
 115         if (nmemb == 0)
 116                 return (0);
 117
 118         /*
 119          * XXX
 120          * Stupid subtraction for the Cray.
 121          */
 122         iflag = 0;
 123         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
 124                 iflag = 1;
 125
 126         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
 127                 return (-1);
 128
 129         list1 = base;
 130         setup(list1, list2, nmemb, size, cmp);
 131         last = list2 + nmemb * size;
 132         i = big = 0;
 133         while (*EVAL(list2) != last) {
 134             l2 = list1;
 135             p1 = EVAL(list1);
 136             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
 137                 p2 = *EVAL(p2);
 138                 f1 = l2;
 139                 f2 = l1 = list1 + (p2 - list2);
 140                 if (p2 != last)
 141                         p2 = *EVAL(p2);
 142                 l2 = list1 + (p2 - list2);
 143                 while (f1 < l1 && f2 < l2) {
 144                         if ((*cmp)(f1, f2) <= 0) {
 145                                 q = f2;
 146                                 b = f1, t = l1;
 147                                 sense = -1;
 148                         } else {
 149                                 q = f1;
 150                                 b = f2, t = l2;
 151                                 sense = 0;
 152                         }
 153                         if (!big) {     /* here i = 0 */
 154                                 while ((b += size) < t && cmp(q, b) >sense)
 155                                         if (++i == 6) {
 156                                                 big = 1;
 157                                                 goto EXPONENTIAL;
 158                                         }
 159                         } else {
 160 EXPONENTIAL:                    for (i = size; ; i <<= 1)
 161                                         if ((p = (b + i)) >= t) {
 162                                                 if ((p = t - size) > b &&
 163                                                     (*cmp)(q, p) <= sense)
 164                                                         t = p;
 165                                                 else
 166                                                         b = p;
 167                                                 break;
 168                                         } else if ((*cmp)(q, p) <= sense) {
 169                                                 t = p;
 170                                                 if (i == size)
 171                                                         big = 0;
 172                                                 goto FASTCASE;
 173                                         } else
 174                                                 b = p;
 175                                 while (t > b+size) {
 176                                         i = (((t - b) / size) >> 1) * size;
 177                                         if ((*cmp)(q, p = b + i) <= sense)
 178                                                 t = p;
 179                                         else
 180                                                 b = p;
 181                                 }
 182                                 goto COPY;
 183 FASTCASE:                       while (i > size)
 184                                         if ((*cmp)(q,
 185                                                 p = b + (i >>= 1)) <= sense)
 186                                                 t = p;
 187                                         else
 188                                                 b = p;
 189 COPY:                           b = t;
 190                         }
 191                         i = size;
 192                         if (q == f1) {
 193                                 if (iflag) {
 194                                         ICOPY_LIST(f2, tp2, b);
 195                                         ICOPY_ELT(f1, tp2, i);
 196                                 } else {
 197                                         CCOPY_LIST(f2, tp2, b);
 198                                         CCOPY_ELT(f1, tp2, i);
 199                                 }
 200                         } else {
 201                                 if (iflag) {
 202                                         ICOPY_LIST(f1, tp2, b);
 203                                         ICOPY_ELT(f2, tp2, i);
 204                                 } else {
 205                                         CCOPY_LIST(f1, tp2, b);
 206                                         CCOPY_ELT(f2, tp2, i);
 207                                 }
 208                         }
 209                 }
 210                 if (f2 < l2) {
 211                         if (iflag)
 212                                 ICOPY_LIST(f2, tp2, l2);
 213                         else
 214                                 CCOPY_LIST(f2, tp2, l2);
 215                 } else if (f1 < l1) {
 216                         if (iflag)
 217                                 ICOPY_LIST(f1, tp2, l1);
 218                         else
 219                                 CCOPY_LIST(f1, tp2, l1);
 220                 }
 221                 *p1 = l2;
 222             }
 223             tp2 = list1;        /* swap list1, list2 */
 224             list1 = list2;
 225             list2 = tp2;
 226             last = list2 + nmemb*size;
 227         }
 228         if (base == list2) {
 229                 memmove(list2, list1, nmemb*size);
 230                 list2 = list1;
 231         }
 232         free(list2);
 233         return (0);
 234 }
 235
 236 #define swap(a, b) {                                    \
 237                 s = b;                                  \
 238                 i = size;                               \
 239                 do {                                    \
 240                         tmp = *a; *a++ = *s; *s++ = tmp; \
 241                 } while (--i);                          \
 242                 a -= size;                              \
 243         }
 244 #define reverse(bot, top) {                             \
 245         s = top;                                        \
 246         do {                                            \
 247                 i = size;                               \
 248                 do {                                    \
 249                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 250                 } while (--i);                          \
 251                 s -= size2;                             \
 252         } while(bot < s);                               \
 253 }
 254
 255 /*
 256  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 257  * increasing order, list2 in a corresponding linked list.  Checks for runs
 258  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 259  * is defined.  Otherwise simple pairwise merging is used.)
 260  */
 261 void
 262 setup(list1, list2, n, size, cmp)
 263         size_t n, size;
 264         int (*cmp)(const void *, const void *);
 265         u_char *list1, *list2;
 266 {
 267         size_t i, size2;
 268         int length, tmp, sense;
 269         u_char *f1, *f2, *s, *l2, *last, *p2;
 270
 271         size2 = size*2;
 272         if (n <= 5) {
 273                 insertionsort(list1, n, size, cmp);
 274                 *EVAL(list2) = (u_char*) list2 + n*size;
 275                 return;
 276         }
 277         /*
 278          * Avoid running pointers out of bounds; limit n to evens
 279          * for simplicity.
 280          */
 281         i = 4 + (n & 1);
 282         insertionsort(list1 + (n - i) * size, i, size, cmp);
 283         last = list1 + size * (n - i);
 284         *EVAL(list2 + (last - list1)) = list2 + n * size;
 285
 286 #ifdef NATURAL
 287         p2 = list2;
 288         f1 = list1;
 289         sense = (cmp(f1, f1 + size) > 0);
 290         for (; f1 < last; sense = !sense) {
 291                 length = 2;
 292                                         /* Find pairs with same sense. */
 293                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 294                         if ((cmp(f2, f2+ size) > 0) != sense)
 295                                 break;
 296                         length += 2;
 297                 }
 298                 if (length < THRESHOLD) {               /* Pairwise merge */
 299                         do {
 300                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 301                                 if (sense > 0)
 302                                         swap (f1, f1 + size);
 303                         } while ((f1 += size2) < f2);
 304                 } else {                                /* Natural merge */
 305                         l2 = f2;
 306                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 307                                 if ((cmp(f2-size, f2) > 0) != sense) {
 308                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 309                                         if (sense > 0)
 310                                                 reverse(f1, f2-size);
 311                                         f1 = f2;
 312                                 }
 313                         }
 314                         if (sense > 0)
 315                                 reverse (f1, f2-size);
 316                         f1 = f2;
 317                         if (f2 < last || cmp(f2 - size, f2) > 0)
 318                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 319                         else
 320                                 p2 = *EVAL(p2) = list2 + n*size;
 321                 }
 322         }
 323 #else           /* pairwise merge only. */
 324         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 325                 p2 = *EVAL(p2) = p2 + size2;
 326                 if (cmp (f1, f1 + size) > 0)
 327                         swap(f1, f1 + size);
 328         }
 329 #endif /* NATURAL */
 330 }
 331
 332 /*
 333  * This is to avoid out-of-bounds addresses in sorting the
 334  * last 4 elements.
 335  */
 336 static void
 337 insertionsort(a, n, size, cmp)
 338         u_char *a;
 339         size_t n, size;
 340         int (*cmp)(const void *, const void *);
 341 {
 342         u_char *ai, *s, *t, *u, tmp;
 343         int i;
 344
 345         for (ai = a+size; --n >= 1; ai += size)
 346                 for (t = ai; t > a; t -= size) {
 347                         u = t - size;
 348                         if (cmp(u, t) <= 0)
 349                                 break;
 350                         swap(u, t);
 351                 }
 352 }