stdlib/qsort.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  * Redistribution and use in source and binary forms, with or without
  27  * modification, are permitted provided that the following conditions
  28  * are met:
  29  * 1. Redistributions of source code must retain the above copyright
  30  *    notice, this list of conditions and the following disclaimer.
  31  * 2. Redistributions in binary form must reproduce the above copyright
  32  *    notice, this list of conditions and the following disclaimer in the
  33  *    documentation and/or other materials provided with the distribution.
  34  * 3. All advertising materials mentioning features or use of this software
  35  *    must display the following acknowledgement:
  36  *      This product includes software developed by the University of
  37  *      California, Berkeley and its contributors.
  38  * 4. Neither the name of the University nor the names of its contributors
  39  *    may be used to endorse or promote products derived from this software
  40  *    without specific prior written permission.
  41  *
  42  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  43  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  44  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  45  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  46  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  47  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  48  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  49  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  50  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  51  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  52  * SUCH DAMAGE.
  53  */
  54
  55
  56 #include <sys/types.h>
  57 #include <stdlib.h>
  58
  59 static inline char      *med3 __P((char *, char *, char *, int (*)()));
  60 static inline void       swapfunc __P((char *, char *, int, int));
  61
  62 #define min(a, b)       (a) < (b) ? a : b
  63
  64 /*
  65  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  66  */
  67 #define swapcode(TYPE, parmi, parmj, n) {               \
  68         long i = (n) / sizeof (TYPE);                   \
  69         register TYPE *pi = (TYPE *) (parmi);           \
  70         register TYPE *pj = (TYPE *) (parmj);           \
  71         do {                                            \
  72                 register TYPE   t = *pi;                \
  73                 *pi++ = *pj;                            \
  74                 *pj++ = t;                              \
  75         } while (--i > 0);                              \
  76 }
  77
  78 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  79         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  80
  81 static inline void
  82 swapfunc(a, b, n, swaptype)
  83         char *a, *b;
  84         int n, swaptype;
  85 {
  86         if(swaptype <= 1)
  87                 swapcode(long, a, b, n)
  88         else
  89                 swapcode(char, a, b, n)
  90 }
  91
  92 #define swap(a, b)                                      \
  93         if (swaptype == 0) {                            \
  94                 long t = *(long *)(a);                  \
  95                 *(long *)(a) = *(long *)(b);            \
  96                 *(long *)(b) = t;                       \
  97         } else                                          \
  98                 swapfunc(a, b, es, swaptype)
  99
 100 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
 101
 102 static inline char *
 103 med3(a, b, c, cmp)
 104         char *a, *b, *c;
 105         int (*cmp)();
 106 {
 107         return cmp(a, b) < 0 ?
 108                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
 109               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
 110 }
 111
 112 void
 113 qsort(a, n, es, cmp)
 114         void *a;
 115         size_t n, es;
 116         int (*cmp)();
 117 {
 118         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 119         int d, r, swaptype, swap_cnt;
 120
 121 loop:   SWAPINIT(a, es);
 122         swap_cnt = 0;
 123         if (n < 7) {
 124                 for (pm = a + es; pm < (char *) a + n * es; pm += es)
 125                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 126                              pl -= es)
 127                                 swap(pl, pl - es);
 128                 return;
 129         }
 130         pm = a + (n / 2) * es;
 131         if (n > 7) {
 132                 pl = a;
 133                 pn = a + (n - 1) * es;
 134                 if (n > 40) {
 135                         d = (n / 8) * es;
 136                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 137                         pm = med3(pm - d, pm, pm + d, cmp);
 138                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 139                 }
 140                 pm = med3(pl, pm, pn, cmp);
 141         }
 142         swap(a, pm);
 143         pa = pb = a + es;
 144
 145         pc = pd = a + (n - 1) * es;
 146         for (;;) {
 147                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
 148                         if (r == 0) {
 149                                 swap_cnt = 1;
 150                                 swap(pa, pb);
 151                                 pa += es;
 152                         }
 153                         pb += es;
 154                 }
 155                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
 156                         if (r == 0) {
 157                                 swap_cnt = 1;
 158                                 swap(pc, pd);
 159                                 pd -= es;
 160                         }
 161                         pc -= es;
 162                 }
 163                 if (pb > pc)
 164                         break;
 165                 swap(pb, pc);
 166                 swap_cnt = 1;
 167                 pb += es;
 168                 pc -= es;
 169         }
 170         if (swap_cnt == 0) {  /* Switch to insertion sort */
 171                 for (pm = a + es; pm < (char *) a + n * es; pm += es)
 172                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 173                              pl -= es)
 174                                 swap(pl, pl - es);
 175                 return;
 176         }
 177
 178         pn = a + n * es;
 179         r = min(pa - (char *)a, pb - pa);
 180         vecswap(a, pb - r, r);
 181         r = min(pd - pc, pn - pd - es);
 182         vecswap(pb, pn - r, r);
 183         if ((r = pb - pa) > es)
 184                 qsort(a, r / es, es, cmp);
 185         if ((r = pd - pc) > es) {
 186                 /* Iterate rather than recurse to save stack space */
 187                 a = pn - r;
 188                 n = r / es;
 189                 goto loop;
 190         }
 191 /*              qsort(pn - r, r / es, es, cmp);*/
 192 }