stdlib.subproj/merge.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1992, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Peter McIlroy.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 /*
  60  * Hybrid exponential search/linear search merge sort with hybrid
  61  * natural/pairwise first pass.  Requires about .3% more comparisons
  62  * for random data than LSMS with pairwise first pass alone.
  63  * It works for objects as small as two bytes.
  64  */
  65
  66 #define NATURAL
  67 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
  68
  69 /* #define NATURAL to get hybrid natural merge.
  70  * (The default is pairwise merging.)
  71  */
  72
  73 #include <sys/types.h>
  74
  75 #include <errno.h>
  76 #include <stdlib.h>
  77 #include <string.h>
  78
  79 static void setup __P((u_char *, u_char *, size_t, size_t, int (*)()));
  80 static void insertionsort __P((u_char *, size_t, size_t, int (*)()));
  81
  82 #define ISIZE sizeof(int)
  83 #define PSIZE sizeof(u_char *)
  84 #define ICOPY_LIST(src, dst, last)                              \
  85         do                                                      \
  86         *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;    \
  87         while(src < last)
  88 #define ICOPY_ELT(src, dst, i)                                  \
  89         do                                                      \
  90         *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;  \
  91         while (i -= ISIZE)
  92
  93 #define CCOPY_LIST(src, dst, last)              \
  94         do                                      \
  95                 *dst++ = *src++;                \
  96         while (src < last)
  97 #define CCOPY_ELT(src, dst, i)                  \
  98         do                                      \
  99                 *dst++ = *src++;                \
 100         while (i -= 1)
 101
 102 /*
 103  * Find the next possible pointer head.  (Trickery for forcing an array
 104  * to do double duty as a linked list when objects do not align with word
 105  * boundaries.
 106  */
 107 /* Assumption: PSIZE is a power of 2. */
 108 #define EVAL(p) (u_char **)                                             \
 109         ((u_char *)0 +                                                  \
 110             (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
 111
 112 /*
 113  * Arguments are as for qsort.
 114  */
 115 int
 116 mergesort(base, nmemb, size, cmp)
 117         void *base;
 118         size_t nmemb;
 119         register size_t size;
 120         int (*cmp) __P((const void *, const void *));
 121 {
 122         register int i, sense;
 123         int big, iflag;
 124         register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
 125         u_char *list2, *list1, *p2, *p, *last, **p1;
 126
 127         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
 128                 errno = EINVAL;
 129                 return (-1);
 130         }
 131
 132         /*
 133          * XXX
 134          * Stupid subtraction for the Cray.
 135          */
 136         iflag = 0;
 137         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
 138                 iflag = 1;
 139
 140         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
 141                 return (-1);
 142
 143         list1 = base;
 144         setup(list1, list2, nmemb, size, cmp);
 145         last = list2 + nmemb * size;
 146         i = big = 0;
 147         while (*EVAL(list2) != last) {
 148             l2 = list1;
 149             p1 = EVAL(list1);
 150             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
 151                 p2 = *EVAL(p2);
 152                 f1 = l2;
 153                 f2 = l1 = list1 + (p2 - list2);
 154                 if (p2 != last)
 155                         p2 = *EVAL(p2);
 156                 l2 = list1 + (p2 - list2);
 157                 while (f1 < l1 && f2 < l2) {
 158                         if ((*cmp)(f1, f2) <= 0) {
 159                                 q = f2;
 160                                 b = f1, t = l1;
 161                                 sense = -1;
 162                         } else {
 163                                 q = f1;
 164                                 b = f2, t = l2;
 165                                 sense = 0;
 166                         }
 167                         if (!big) {     /* here i = 0 */
 168 LINEAR:                         while ((b += size) < t && cmp(q, b) >sense)
 169                                         if (++i == 6) {
 170                                                 big = 1;
 171                                                 goto EXPONENTIAL;
 172                                         }
 173                         } else {
 174 EXPONENTIAL:                    for (i = size; ; i <<= 1)
 175                                         if ((p = (b + i)) >= t) {
 176                                                 if ((p = t - size) > b &&
 177                                                     (*cmp)(q, p) <= sense)
 178                                                         t = p;
 179                                                 else
 180                                                         b = p;
 181                                                 break;
 182                                         } else if ((*cmp)(q, p) <= sense) {
 183                                                 t = p;
 184                                                 if (i == size)
 185                                                         big = 0;
 186                                                 goto FASTCASE;
 187                                         } else
 188                                                 b = p;
 189 SLOWCASE:                       while (t > b+size) {
 190                                         i = (((t - b) / size) >> 1) * size;
 191                                         if ((*cmp)(q, p = b + i) <= sense)
 192                                                 t = p;
 193                                         else
 194                                                 b = p;
 195                                 }
 196                                 goto COPY;
 197 FASTCASE:                       while (i > size)
 198                                         if ((*cmp)(q,
 199                                                 p = b + (i >>= 1)) <= sense)
 200                                                 t = p;
 201                                         else
 202                                                 b = p;
 203 COPY:                           b = t;
 204                         }
 205                         i = size;
 206                         if (q == f1) {
 207                                 if (iflag) {
 208                                         ICOPY_LIST(f2, tp2, b);
 209                                         ICOPY_ELT(f1, tp2, i);
 210                                 } else {
 211                                         CCOPY_LIST(f2, tp2, b);
 212                                         CCOPY_ELT(f1, tp2, i);
 213                                 }
 214                         } else {
 215                                 if (iflag) {
 216                                         ICOPY_LIST(f1, tp2, b);
 217                                         ICOPY_ELT(f2, tp2, i);
 218                                 } else {
 219                                         CCOPY_LIST(f1, tp2, b);
 220                                         CCOPY_ELT(f2, tp2, i);
 221                                 }
 222                         }
 223                 }
 224                 if (f2 < l2) {
 225                         if (iflag)
 226                                 ICOPY_LIST(f2, tp2, l2);
 227                         else
 228                                 CCOPY_LIST(f2, tp2, l2);
 229                 } else if (f1 < l1) {
 230                         if (iflag)
 231                                 ICOPY_LIST(f1, tp2, l1);
 232                         else
 233                                 CCOPY_LIST(f1, tp2, l1);
 234                 }
 235                 *p1 = l2;
 236             }
 237             tp2 = list1;        /* swap list1, list2 */
 238             list1 = list2;
 239             list2 = tp2;
 240             last = list2 + nmemb*size;
 241         }
 242         if (base == list2) {
 243                 memmove(list2, list1, nmemb*size);
 244                 list2 = list1;
 245         }
 246         free(list2);
 247         return (0);
 248 }
 249
 250 #define swap(a, b) {                                    \
 251                 s = b;                                  \
 252                 i = size;                               \
 253                 do {                                    \
 254                         tmp = *a; *a++ = *s; *s++ = tmp; \
 255                 } while (--i);                          \
 256                 a -= size;                              \
 257         }
 258 #define reverse(bot, top) {                             \
 259         s = top;                                        \
 260         do {                                            \
 261                 i = size;                               \
 262                 do {                                    \
 263                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
 264                 } while (--i);                          \
 265                 s -= size2;                             \
 266         } while(bot < s);                               \
 267 }
 268
 269 /*
 270  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
 271  * increasing order, list2 in a corresponding linked list.  Checks for runs
 272  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
 273  * is defined.  Otherwise simple pairwise merging is used.)
 274  */
 275 void
 276 setup(list1, list2, n, size, cmp)
 277         size_t n, size;
 278         int (*cmp) __P((const void *, const void *));
 279         u_char *list1, *list2;
 280 {
 281         int i, length, size2, tmp, sense;
 282         u_char *f1, *f2, *s, *l2, *last, *p2;
 283
 284         size2 = size*2;
 285         if (n <= 5) {
 286                 insertionsort(list1, n, size, cmp);
 287                 *EVAL(list2) = (u_char*) list2 + n*size;
 288                 return;
 289         }
 290         /*
 291          * Avoid running pointers out of bounds; limit n to evens
 292          * for simplicity.
 293          */
 294         i = 4 + (n & 1);
 295         insertionsort(list1 + (n - i) * size, i, size, cmp);
 296         last = list1 + size * (n - i);
 297         *EVAL(list2 + (last - list1)) = list2 + n * size;
 298
 299 #ifdef NATURAL
 300         p2 = list2;
 301         f1 = list1;
 302         sense = (cmp(f1, f1 + size) > 0);
 303         for (; f1 < last; sense = !sense) {
 304                 length = 2;
 305                                         /* Find pairs with same sense. */
 306                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
 307                         if ((cmp(f2, f2+ size) > 0) != sense)
 308                                 break;
 309                         length += 2;
 310                 }
 311                 if (length < THRESHOLD) {               /* Pairwise merge */
 312                         do {
 313                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
 314                                 if (sense > 0)
 315                                         swap (f1, f1 + size);
 316                         } while ((f1 += size2) < f2);
 317                 } else {                                /* Natural merge */
 318                         l2 = f2;
 319                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
 320                                 if ((cmp(f2-size, f2) > 0) != sense) {
 321                                         p2 = *EVAL(p2) = f2 - list1 + list2;
 322                                         if (sense > 0)
 323                                                 reverse(f1, f2-size);
 324                                         f1 = f2;
 325                                 }
 326                         }
 327                         if (sense > 0)
 328                                 reverse (f1, f2-size);
 329                         f1 = f2;
 330                         if (f2 < last || cmp(f2 - size, f2) > 0)
 331                                 p2 = *EVAL(p2) = f2 - list1 + list2;
 332                         else
 333                                 p2 = *EVAL(p2) = list2 + n*size;
 334                 }
 335         }
 336 #else           /* pairwise merge only. */
 337         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
 338                 p2 = *EVAL(p2) = p2 + size2;
 339                 if (cmp (f1, f1 + size) > 0)
 340                         swap(f1, f1 + size);
 341         }
 342 #endif /* NATURAL */
 343 }
 344
 345 /*
 346  * This is to avoid out-of-bounds addresses in sorting the
 347  * last 4 elements.
 348  */
 349 static void
 350 insertionsort(a, n, size, cmp)
 351         u_char *a;
 352         size_t n, size;
 353         int (*cmp) __P((const void *, const void *));
 354 {
 355         u_char *ai, *s, *t, *u, tmp;
 356         int i;
 357
 358         for (ai = a+size; --n >= 1; ai += size)
 359                 for (t = ai; t > a; t -= size) {
 360                         u = t - size;
 361                         if (cmp(u, t) <= 0)
 362                                 break;
 363                         swap(u, t);
 364                 }
 365 }