src/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) 2009-2010 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/types.h>
  41
  42 #include <assert.h>
  43 #include <errno.h>
  44 #include <stdlib.h>
  45
  46 static inline char      *med3 (char *, char *, char *,
  47     int (*)(const void *, const void *));
  48 static inline void       swapfunc (char *, char *, size_t, int);
  49
  50 #define min(a, b)       (a) < (b) ? a : b
  51
  52 /*
  53  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  54  */
  55 #define swapcode(TYPE, parmi, parmj, n) {               \
  56         size_t i = (n) / sizeof (TYPE);                 \
  57         TYPE *pi = (TYPE *)(void *)(parmi);             \
  58         TYPE *pj = (TYPE *)(void *)(parmj);             \
  59         do {                                            \
  60                 TYPE    t = *pi;                        \
  61                 *pi++ = *pj;                            \
  62                 *pj++ = t;                              \
  63         } while (--i > 0);                              \
  64 }
  65
  66 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  67         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  68
  69 static inline void
  70 swapfunc(char *a, char *b, size_t n, int swaptype)
  71 {
  72
  73         if (swaptype <= 1)
  74                 swapcode(long, a, b, n)
  75         else
  76                 swapcode(char, a, b, n)
  77 }
  78
  79 #define swap(a, b)                                              \
  80         if (swaptype == 0) {                                    \
  81                 long t = *(long *)(void *)(a);                  \
  82                 *(long *)(void *)(a) = *(long *)(void *)(b);    \
  83                 *(long *)(void *)(b) = t;                       \
  84         } else                                                  \
  85                 swapfunc(a, b, es, swaptype)
  86
  87 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
  88
  89 static inline char *
  90 med3(char *a, char *b, char *c,
  91     int (*cmp) (const void *, const void *))
  92 {
  93
  94         return cmp(a, b) < 0 ?
  95                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
  96               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
  97 }
  98
  99 static void
 100 _pqsort(void *a, size_t n, size_t es,
 101     int (*cmp) (const void *, const void *), void *lrange, void *rrange)
 102 {
 103         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 104         size_t d, r;
 105         int swaptype, swap_cnt, cmp_result;
 106
 107 loop:   SWAPINIT(a, es);
 108         swap_cnt = 0;
 109         if (n < 7) {
 110                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 111                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 112                              pl -= es)
 113                                 swap(pl, pl - es);
 114                 return;
 115         }
 116         pm = (char *) a + (n / 2) * es;
 117         if (n > 7) {
 118                 pl = (char *) a;
 119                 pn = (char *) a + (n - 1) * es;
 120                 if (n > 40) {
 121                         d = (n / 8) * es;
 122                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 123                         pm = med3(pm - d, pm, pm + d, cmp);
 124                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 125                 }
 126                 pm = med3(pl, pm, pn, cmp);
 127         }
 128         swap(a, pm);
 129         pa = pb = (char *) a + es;
 130
 131         pc = pd = (char *) a + (n - 1) * es;
 132         for (;;) {
 133                 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
 134                         if (cmp_result == 0) {
 135                                 swap_cnt = 1;
 136                                 swap(pa, pb);
 137                                 pa += es;
 138                         }
 139                         pb += es;
 140                 }
 141                 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
 142                         if (cmp_result == 0) {
 143                                 swap_cnt = 1;
 144                                 swap(pc, pd);
 145                                 pd -= es;
 146                         }
 147                         pc -= es;
 148                 }
 149                 if (pb > pc)
 150                         break;
 151                 swap(pb, pc);
 152                 swap_cnt = 1;
 153                 pb += es;
 154                 pc -= es;
 155         }
 156         if (swap_cnt == 0) {  /* Switch to insertion sort */
 157                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 158                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 159                              pl -= es)
 160                                 swap(pl, pl - es);
 161                 return;
 162         }
 163
 164         pn = (char *) a + n * es;
 165         r = min(pa - (char *) a, pb - pa);
 166         vecswap(a, pb - r, r);
 167         r = min((size_t)(pd - pc), pn - pd - es);
 168         vecswap(pb, pn - r, r);
 169         if ((r = pb - pa) > es) {
 170                 void *_l = a, *_r = ((unsigned char*)a)+r-1;
 171                 if (!((lrange < _l && rrange < _l) ||
 172                     (lrange > _r && rrange > _r)))
 173                     _pqsort(a, r / es, es, cmp, lrange, rrange);
 174         }
 175         if ((r = pd - pc) > es) {
 176                 void *_l, *_r;
 177
 178                 /* Iterate rather than recurse to save stack space */
 179                 a = pn - r;
 180                 n = r / es;
 181
 182                 _l = a;
 183                 _r = ((unsigned char*)a)+r-1;
 184                 if (!((lrange < _l && rrange < _l) ||
 185                     (lrange > _r && rrange > _r)))
 186                     goto loop;
 187         }
 188 /*              qsort(pn - r, r / es, es, cmp);*/
 189 }
 190
 191 void
 192 pqsort(void *a, size_t n, size_t es,
 193     int (*cmp) (const void *, const void *), size_t lrange, size_t rrange)
 194 {
 195     _pqsort(a,n,es,cmp,((unsigned char*)a)+(lrange*es),
 196                        ((unsigned char*)a)+((rrange+1)*es)-1);
 197 }