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 #include <sys/cdefs.h>
  41 #if defined(LIBC_SCCS) && !defined(lint)
  42 #if 0
  43 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  44 #else
  45 __RCSID("$NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem Exp $");
  46 #endif
  47 #endif /* LIBC_SCCS and not lint */
  48
  49 #include <sys/types.h>
  50
  51 #include <assert.h>
  52 #include <errno.h>
  53 #include <stdlib.h>
  54
  55 static inline char      *med3 __P((char *, char *, char *,
  56     int (*)(const void *, const void *)));
  57 static inline void       swapfunc __P((char *, char *, size_t, int));
  58
  59 #define min(a, b)       (a) < (b) ? a : b
  60
  61 /*
  62  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  63  */
  64 #define swapcode(TYPE, parmi, parmj, n) {               \
  65         size_t i = (n) / sizeof (TYPE);                 \
  66         TYPE *pi = (TYPE *)(void *)(parmi);             \
  67         TYPE *pj = (TYPE *)(void *)(parmj);             \
  68         do {                                            \
  69                 TYPE    t = *pi;                        \
  70                 *pi++ = *pj;                            \
  71                 *pj++ = t;                              \
  72         } while (--i > 0);                              \
  73 }
  74
  75 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  76         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  77
  78 static inline void
  79 swapfunc(char *a, char *b, size_t n, int swaptype)
  80 {
  81
  82         if (swaptype <= 1)
  83                 swapcode(long, a, b, n)
  84         else
  85                 swapcode(char, a, b, n)
  86 }
  87
  88 #define swap(a, b)                                              \
  89         if (swaptype == 0) {                                    \
  90                 long t = *(long *)(void *)(a);                  \
  91                 *(long *)(void *)(a) = *(long *)(void *)(b);    \
  92                 *(long *)(void *)(b) = t;                       \
  93         } else                                                  \
  94                 swapfunc(a, b, es, swaptype)
  95
  96 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
  97
  98 static inline char *
  99 med3(char *a, char *b, char *c,
 100     int (*cmp) __P((const void *, const void *)))
 101 {
 102
 103         return cmp(a, b) < 0 ?
 104                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
 105               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
 106 }
 107
 108 static void
 109 _pqsort(void *a, size_t n, size_t es,
 110     int (*cmp) __P((const void *, const void *)), void *lrange, void *rrange)
 111 {
 112         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 113         size_t d, r;
 114         int swaptype, swap_cnt, cmp_result;
 115
 116 loop:   SWAPINIT(a, es);
 117         swap_cnt = 0;
 118         if (n < 7) {
 119                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 120                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 121                              pl -= es)
 122                                 swap(pl, pl - es);
 123                 return;
 124         }
 125         pm = (char *) a + (n / 2) * es;
 126         if (n > 7) {
 127                 pl = (char *) a;
 128                 pn = (char *) a + (n - 1) * es;
 129                 if (n > 40) {
 130                         d = (n / 8) * es;
 131                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 132                         pm = med3(pm - d, pm, pm + d, cmp);
 133                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 134                 }
 135                 pm = med3(pl, pm, pn, cmp);
 136         }
 137         swap(a, pm);
 138         pa = pb = (char *) a + es;
 139
 140         pc = pd = (char *) a + (n - 1) * es;
 141         for (;;) {
 142                 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
 143                         if (cmp_result == 0) {
 144                                 swap_cnt = 1;
 145                                 swap(pa, pb);
 146                                 pa += es;
 147                         }
 148                         pb += es;
 149                 }
 150                 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
 151                         if (cmp_result == 0) {
 152                                 swap_cnt = 1;
 153                                 swap(pc, pd);
 154                                 pd -= es;
 155                         }
 156                         pc -= es;
 157                 }
 158                 if (pb > pc)
 159                         break;
 160                 swap(pb, pc);
 161                 swap_cnt = 1;
 162                 pb += es;
 163                 pc -= es;
 164         }
 165         if (swap_cnt == 0) {  /* Switch to insertion sort */
 166                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 167                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 168                              pl -= es)
 169                                 swap(pl, pl - es);
 170                 return;
 171         }
 172
 173         pn = (char *) a + n * es;
 174         r = min(pa - (char *) a, pb - pa);
 175         vecswap(a, pb - r, r);
 176         r = min((size_t)(pd - pc), pn - pd - es);
 177         vecswap(pb, pn - r, r);
 178         if ((r = pb - pa) > es) {
 179                 void *_l = a, *_r = ((unsigned char*)a)+r-1;
 180                 if (!((lrange < _l && rrange < _l) ||
 181                     (lrange > _r && rrange > _r)))
 182                     _pqsort(a, r / es, es, cmp, lrange, rrange);
 183         }
 184         if ((r = pd - pc) > es) {
 185                 void *_l, *_r;
 186
 187                 /* Iterate rather than recurse to save stack space */
 188                 a = pn - r;
 189                 n = r / es;
 190
 191                 _l = a;
 192                 _r = ((unsigned char*)a)+r-1;
 193                 if (!((lrange < _l && rrange < _l) ||
 194                     (lrange > _r && rrange > _r)))
 195                     goto loop;
 196         }
 197 /*              qsort(pn - r, r / es, es, cmp);*/
 198 }
 199
 200 void
 201 pqsort(void *a, size_t n, size_t es,
 202     int (*cmp) __P((const void *, const void *)), size_t lrange, size_t rrange)
 203 {
 204     _pqsort(a,n,es,cmp,((unsigned char*)a)+(lrange*es),
 205                        ((unsigned char*)a)+((rrange+1)*es)-1);
 206 }