stdlib/FreeBSD/qsort.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  32 #endif /* LIBC_SCCS and not lint */
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include <stdbool.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39
  40 #ifdef I_AM_QSORT_R
  41 typedef int              cmp_t(void *, const void *, const void *);
  42 #else
  43 typedef int              cmp_t(const void *, const void *);
  44 #endif
  45 static inline char      *med3(char *, char *, char *, cmp_t *, void *);
  46 static inline void       swapfunc(char *, char *, size_t, int, int);
  47
  48 #define MIN(a, b)       ((a) < (b) ? a : b)
  49
  50 /*
  51  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  52  */
  53 #define swapcode(TYPE, parmi, parmj, n) {               \
  54         size_t i = (n) / sizeof (TYPE);                 \
  55         TYPE *pi = (TYPE *) (parmi);            \
  56         TYPE *pj = (TYPE *) (parmj);            \
  57         do {                                            \
  58                 TYPE    t = *pi;                \
  59                 *pi++ = *pj;                            \
  60                 *pj++ = t;                              \
  61         } while (--i > 0);                              \
  62 }
  63
  64 #define SWAPINIT(TYPE, a, es) swaptype_ ## TYPE =       \
  65         ((char *)a - (char *)0) % sizeof(TYPE) ||       \
  66         es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1;
  67
  68 static inline void
  69 swapfunc(char *a, char *b, size_t n, int swaptype_long, int swaptype_int)
  70 {
  71         if (swaptype_long <= 1)
  72                 swapcode(long, a, b, n)
  73         else if (swaptype_int <= 1)
  74                 swapcode(int, a, b, n)
  75         else
  76                 swapcode(char, a, b, n)
  77 }
  78
  79 #define swap(a, b)                                      \
  80         if (swaptype_long == 0) {                       \
  81                 long t = *(long *)(a);                  \
  82                 *(long *)(a) = *(long *)(b);            \
  83                 *(long *)(b) = t;                       \
  84         } else if (swaptype_int == 0) {                 \
  85                 int t = *(int *)(a);                    \
  86                 *(int *)(a) = *(int *)(b);              \
  87                 *(int *)(b) = t;                        \
  88         } else                                          \
  89                 swapfunc(a, b, es, swaptype_long, swaptype_int)
  90
  91 #define vecswap(a, b, n)                                \
  92         if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int)
  93
  94 #ifdef I_AM_QSORT_R
  95 #define CMP(t, x, y) (cmp((t), (x), (y)))
  96 #else
  97 #define CMP(t, x, y) (cmp((x), (y)))
  98 #endif
  99
 100 /*
 101  * Find the median of 3 elements
 102  */
 103 static inline char *
 104 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
 105 #ifndef I_AM_QSORT_R
 106 __unused
 107 #endif
 108 )
 109 {
 110         return CMP(thunk, a, b) < 0 ?
 111                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
 112               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
 113 }
 114
 115 #ifdef __LP64__
 116 #define DEPTH(x)        (2 * (flsl((long)(x)) - 1))
 117 #else /* !__LP64__ */
 118 #define DEPTH(x)        (2 * (fls((int)(x)) - 1))
 119 #endif /* __LP64__ */
 120
 121 #ifdef I_AM_QSORT_R
 122 int __heapsort_r(void *, size_t, size_t, void *, int (*)(void *, const void *, const void *));
 123 #endif
 124
 125 /*
 126  * Simple insertion sort routine.
 127  */
 128 static bool
 129 _isort(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp, int swap_limit, int swaptype_long, int swaptype_int)
 130 {
 131         int swap_cnt = 0;
 132         for (char *pm = (char *)a + es; pm < (char *)a + n * es; pm += es) {
 133                 for (char *pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 134                                 pl -= es) {
 135                         swap(pl, pl - es);
 136                         if (swap_limit && ++swap_cnt > swap_limit) return false;
 137                 }
 138         }
 139         return true;
 140 }
 141
 142 #ifdef I_AM_QSORT_R
 143 static void
 144 _qsort(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp, int depth_limit)
 145 #else
 146 #define thunk NULL
 147 static void
 148 _qsort(void *a, size_t n, size_t es, cmp_t *cmp, int depth_limit)
 149 #endif
 150 {
 151         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 152         size_t d1, d2;
 153         int cmp_result;
 154         int swaptype_long, swaptype_int, swap_cnt;
 155
 156 loop:
 157         SWAPINIT(long, a, es);
 158         SWAPINIT(int, a, es);
 159         swap_cnt = 0;
 160
 161         if (depth_limit-- <= 0) {
 162                 /*
 163                  * We've hit our recursion limit, switch to heapsort
 164                  */
 165 #ifdef I_AM_QSORT_R
 166                 __heapsort_r(a, n, es, thunk, cmp);
 167 #else
 168                 heapsort(a, n, es, cmp);
 169 #endif
 170                 return;
 171         }
 172
 173         if (n <= 7) {
 174                 /*
 175                  * For sufficiently small inputs, we'll just insertion sort.
 176                  *
 177                  * Pass 0 as swap limit, since this must complete.
 178                  */
 179                 _isort(a, n, es, thunk, cmp, 0, swaptype_long, swaptype_int);
 180                 return;
 181         }
 182
 183         /*
 184          * Compute the pseudomedian.  Small arrays use 3 samples, large ones use 9.
 185          */
 186         pl = a;
 187         pm = (char *)a + (n / 2) * es;
 188         pn = (char *)a + (n - 1) * es;
 189         if (n > 40) {
 190                 size_t d = (n / 8) * es;
 191
 192                 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
 193                 pm = med3(pm - d, pm, pm + d, cmp, thunk);
 194                 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
 195         }
 196         pm = med3(pl, pm, pn, cmp, thunk);
 197
 198         /*
 199          * Pull the median to the front, starting us with:
 200          *
 201          * +-+-------------+
 202          * |=|      ?      |
 203          * +-+-------------+
 204          * a pa,pb         pc,pd
 205          */
 206         swap(a, pm);
 207         pa = pb = (char *)a + es;
 208         pc = pd = (char *)a + (n - 1) * es;
 209
 210         for (;;) {
 211                 /*
 212                  * - Move b forward while it's less than the median
 213                  * - Move c backwards while it's greater than the median
 214                  * - When equal to the median, swap to the outside
 215                  */
 216                 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
 217                         if (cmp_result == 0) {
 218                                 swap_cnt = 1;
 219                                 swap(pa, pb);
 220                                 pa += es;
 221                         }
 222                         pb += es;
 223                 }
 224                 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
 225                         if (cmp_result == 0) {
 226                                 swap_cnt = 1;
 227                                 swap(pc, pd);
 228                                 pd -= es;
 229                         }
 230                         pc -= es;
 231                 }
 232                 if (pb > pc)
 233                         break;
 234                 swap(pb, pc);
 235                 swap_cnt = 1;
 236                 pb += es;
 237                 pc -= es;
 238         }
 239
 240         /*
 241          * Now we've got:
 242          *
 243          * +---+-----+-----+---+
 244          * | = |  <  |  >  | = |
 245          * +---+-----+-----+---+
 246          * a   pa  pc,pb   pd  pn
 247          *
 248          * So swap the '=' into the middle
 249          */
 250
 251         pn = (char *)a + n * es;
 252         d1 = MIN(pa - (char *)a, pb - pa);
 253         vecswap(a, pb - d1, d1);
 254         d1 = MIN(pd - pc, pn - pd - es);
 255         vecswap(pb, pn - d1, d1);
 256
 257         /*
 258          * +-----+---+---+-----+
 259          * |  <  |   =   |  >  |
 260          * +-----+---+---+-----+
 261          * a                   pn
 262          */
 263
 264         if (swap_cnt == 0) {  /* Switch to insertion sort */
 265                 int r = 1 + n / 4; /* n > 7, so r >= 2 */
 266                 if (!_isort(a, n, es, thunk, cmp, r, swaptype_long, swaptype_int)) {
 267                         goto nevermind;
 268                 }
 269                 return;
 270         }
 271 nevermind:
 272
 273         d1 = pb - pa;
 274         d2 = pd - pc;
 275         if (d1 <= d2) {
 276                 /* Recurse on left partition, then iterate on right partition */
 277                 if (d1 > es) {
 278 #ifdef I_AM_QSORT_R
 279                         _qsort(a, d1 / es, es, thunk, cmp, depth_limit);
 280 #else
 281                         _qsort(a, d1 / es, es, cmp, depth_limit);
 282 #endif
 283                 }
 284                 if (d2 > es) {
 285                         /* Iterate rather than recurse to save stack space */
 286                         /* qsort(pn - d2, d2 / es, es, cmp); */
 287                         a = pn - d2;
 288                         n = d2 / es;
 289                         goto loop;
 290                 }
 291         } else {
 292                 /* Recurse on right partition, then iterate on left partition */
 293                 if (d2 > es) {
 294 #ifdef I_AM_QSORT_R
 295                         _qsort(pn - d2, d2 / es, es, thunk, cmp, depth_limit);
 296 #else
 297                         _qsort(pn - d2, d2 / es, es, cmp, depth_limit);
 298 #endif
 299                 }
 300                 if (d1 > es) {
 301                         /* Iterate rather than recurse to save stack space */
 302                         /* qsort(a, d1 / es, es, cmp); */
 303                         n = d1 / es;
 304                         goto loop;
 305                 }
 306         }
 307 }
 308
 309 void
 310 #ifdef I_AM_QSORT_R
 311 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
 312 #else
 313 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 314 #endif
 315 {
 316         _qsort(a, n, es,
 317 #ifdef I_AM_QSORT_R
 318                 thunk,
 319 #endif
 320                 cmp, DEPTH(n));
 321 }