pqsort.c

   1 /* The following is the NetBSD libc qsort implementation modified in order to
   2  * support partial sorting of ranges for Redis.
   3  *
   4  * Copyright(C) 2009 Salvatore Sanfilippo. All rights reserved.
   5  *
   6  * The original copyright notice follows. */
   7
   8
   9 /*      $NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem Exp $ */
  10
  11 /*-
  12  * Copyright (c) 1992, 1993
  13  *      The Regents of the University of California.  All rights reserved.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions
  17  * are met:
  18  * 1. Redistributions of source code must retain the above copyright
  19  *    notice, this list of conditions and the following disclaimer.
  20  * 2. Redistributions in binary form must reproduce the above copyright
  21  *    notice, this list of conditions and the following disclaimer in the
  22  *    documentation and/or other materials provided with the distribution.
  23  * 3. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  */
  39
  40 #define __P(protos) protos
  41
  42 #include <sys/cdefs.h>
  43 #if defined(LIBC_SCCS) && !defined(lint)
  44 #if 0
  45 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  46 #else
  47 __RCSID("$NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem Exp $");
  48 #endif
  49 #endif /* LIBC_SCCS and not lint */
  50
  51 #include <sys/types.h>
  52
  53 #include <assert.h>
  54 #include <errno.h>
  55 #include <stdlib.h>
  56
  57 static inline char      *med3 __P((char *, char *, char *,
  58     int (*)(const void *, const void *)));
  59 static inline void       swapfunc __P((char *, char *, size_t, int));
  60
  61 #define min(a, b)       (a) < (b) ? a : b
  62
  63 /*
  64  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  65  */
  66 #define swapcode(TYPE, parmi, parmj, n) {               \
  67         size_t i = (n) / sizeof (TYPE);                 \
  68         TYPE *pi = (TYPE *)(void *)(parmi);             \
  69         TYPE *pj = (TYPE *)(void *)(parmj);             \
  70         do {                                            \
  71                 TYPE    t = *pi;                        \
  72                 *pi++ = *pj;                            \
  73                 *pj++ = t;                              \
  74         } while (--i > 0);                              \
  75 }
  76
  77 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  78         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  79
  80 static inline void
  81 swapfunc(char *a, char *b, size_t n, int swaptype)
  82 {
  83
  84         if (swaptype <= 1)
  85                 swapcode(long, a, b, n)
  86         else
  87                 swapcode(char, a, b, n)
  88 }
  89
  90 #define swap(a, b)                                              \
  91         if (swaptype == 0) {                                    \
  92                 long t = *(long *)(void *)(a);                  \
  93                 *(long *)(void *)(a) = *(long *)(void *)(b);    \
  94                 *(long *)(void *)(b) = t;                       \
  95         } else                                                  \
  96                 swapfunc(a, b, es, swaptype)
  97
  98 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
  99
 100 static inline char *
 101 med3(char *a, char *b, char *c,
 102     int (*cmp) __P((const void *, const void *)))
 103 {
 104
 105         return cmp(a, b) < 0 ?
 106                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
 107               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
 108 }
 109
 110 static void
 111 _pqsort(void *a, size_t n, size_t es,
 112     int (*cmp) __P((const void *, const void *)), void *lrange, void *rrange)
 113 {
 114         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 115         size_t d, r;
 116         int swaptype, swap_cnt, cmp_result;
 117
 118 loop:   SWAPINIT(a, es);
 119         swap_cnt = 0;
 120         if (n < 7) {
 121                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 122                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 123                              pl -= es)
 124                                 swap(pl, pl - es);
 125                 return;
 126         }
 127         pm = (char *) a + (n / 2) * es;
 128         if (n > 7) {
 129                 pl = (char *) a;
 130                 pn = (char *) a + (n - 1) * es;
 131                 if (n > 40) {
 132                         d = (n / 8) * es;
 133                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 134                         pm = med3(pm - d, pm, pm + d, cmp);
 135                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 136                 }
 137                 pm = med3(pl, pm, pn, cmp);
 138         }
 139         swap(a, pm);
 140         pa = pb = (char *) a + es;
 141
 142         pc = pd = (char *) a + (n - 1) * es;
 143         for (;;) {
 144                 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
 145                         if (cmp_result == 0) {
 146                                 swap_cnt = 1;
 147                                 swap(pa, pb);
 148                                 pa += es;
 149                         }
 150                         pb += es;
 151                 }
 152                 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
 153                         if (cmp_result == 0) {
 154                                 swap_cnt = 1;
 155                                 swap(pc, pd);
 156                                 pd -= es;
 157                         }
 158                         pc -= es;
 159                 }
 160                 if (pb > pc)
 161                         break;
 162                 swap(pb, pc);
 163                 swap_cnt = 1;
 164                 pb += es;
 165                 pc -= es;
 166         }
 167         if (swap_cnt == 0) {  /* Switch to insertion sort */
 168                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 169                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 170                              pl -= es)
 171                                 swap(pl, pl - es);
 172                 return;
 173         }
 174
 175         pn = (char *) a + n * es;
 176         r = min(pa - (char *) a, pb - pa);
 177         vecswap(a, pb - r, r);
 178         r = min((size_t)(pd - pc), pn - pd - es);
 179         vecswap(pb, pn - r, r);
 180         if ((r = pb - pa) > es) {
 181                 void *_l = a, *_r = ((unsigned char*)a)+r-1;
 182                 if (!((lrange < _l && rrange < _l) ||
 183                     (lrange > _r && rrange > _r)))
 184                     _pqsort(a, r / es, es, cmp, lrange, rrange);
 185         }
 186         if ((r = pd - pc) > es) {
 187                 void *_l, *_r;
 188
 189                 /* Iterate rather than recurse to save stack space */
 190                 a = pn - r;
 191                 n = r / es;
 192
 193                 _l = a;
 194                 _r = ((unsigned char*)a)+r-1;
 195                 if (!((lrange < _l && rrange < _l) ||
 196                     (lrange > _r && rrange > _r)))
 197                     goto loop;
 198         }
 199 /*              qsort(pn - r, r / es, es, cmp);*/
 200 }
 201
 202 void
 203 pqsort(void *a, size_t n, size_t es,
 204     int (*cmp) __P((const void *, const void *)), size_t lrange, size_t rrange)
 205 {
 206     _pqsort(a,n,es,cmp,((unsigned char*)a)+(lrange*es),
 207                        ((unsigned char*)a)+((rrange+1)*es)-1);
 208 }