unix4lyfe git - darkstat/blob - hosts_sort.c

   1 /* darkstat 3
   2  * copyright (c) 2001-2006 Emil Mikulic.
   3  *
   4  * hosts_sort.c: quicksort a table of buckets.
   5  *
   6  * You may use, modify and redistribute this file under the terms of the
   7  * GNU General Public License version 2. (see COPYING.GPL)
   8  */
   9
  10 #include "darkstat.h"
  11 #include "hosts_db.h"
  12 #include "err.h"
  13
  14 /* ---------------------------------------------------------------------------
  15  * comparator for sorting (biggest first)
  16  */
  17 static int
  18 cmp(const struct bucket * const *x, const struct bucket * const *y,
  19     const enum sort_dir dir)
  20 {
  21    uint64_t a, b;
  22
  23    switch (dir) {
  24    case IN:
  25       a = (*x)->in;
  26       b = (*y)->in;
  27       break;
  28    case OUT:
  29       a = (*x)->out;
  30       b = (*y)->out;
  31       break;
  32    case TOTAL:
  33       a = (*x)->total;
  34       b = (*y)->total;
  35       break;
  36    default:
  37       errx(1, "cmp: unknown direction: %d", dir);
  38    }
  39
  40    if (a < b) return (1);
  41    else if (a > b) return (-1);
  42    else return (0);
  43 }
  44
  45 /*
  46  * The quicksort code is derived from FreeBSD's
  47  * src/lib/libc/stdlib/qsort.c v1.12
  48  */
  49
  50 /*-
  51  * Copyright (c) 1992, 1993
  52  *     The Regents of the University of California.  All rights reserved.
  53  *
  54  * Redistribution and use in source and binary forms, with or without
  55  * modification, are permitted provided that the following conditions
  56  * are met:
  57  * 1. Redistributions of source code must retain the above copyright
  58  *    notice, this list of conditions and the following disclaimer.
  59  * 2. Redistributions in binary form must reproduce the above copyright
  60  *    notice, this list of conditions and the following disclaimer in the
  61  *    documentation and/or other materials provided with the distribution.
  62  * 3. All advertising materials mentioning features or use of this software
  63  *    must display the following acknowledgement:
  64  *     This product includes software developed by the University of
  65  *     California, Berkeley and its contributors.
  66  * 4. Neither the name of the University nor the names of its contributors
  67  *    may be used to endorse or promote products derived from this software
  68  *    without specific prior written permission.
  69  *
  70  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  71  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  72  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  73  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  74  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  75  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  76  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  77  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  78  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  79  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  80  * SUCH DAMAGE.
  81  */
  82
  83 static void
  84 vecswap(const struct bucket **pi, const struct bucket **pj, int n)
  85 {
  86    if (n <= 0)
  87       return;
  88
  89    do {
  90       const struct bucket *t = *pi;
  91       *pi++ = *pj;
  92       *pj++ = t;
  93    } while (--n > 0);
  94 }
  95
  96 #define swap(a, b) { \
  97    const struct bucket *t = *(const struct bucket **)(a); \
  98    *(const struct bucket **)(a) = *(const struct bucket **)(b); \
  99    *(const struct bucket **)(b) = t; \
 100 }
 101
 102 static const struct bucket **
 103 med3(const struct bucket **a,
 104      const struct bucket **b,
 105      const struct bucket **c,
 106      const enum sort_dir dir)
 107 {
 108    return (cmp(a, b, dir) < 0)
 109     ? (cmp(b, c, dir) < 0 ? b : (cmp(a, c, dir) < 0 ? c : a ))
 110     : (cmp(b, c, dir) > 0 ? b : (cmp(a, c, dir) < 0 ? a : c ));
 111 }
 112
 113 /* Partial sort - only sort elements in the range [left:right] */
 114 void
 115 qsort_buckets(const struct bucket **a, size_t n,
 116    size_t left, size_t right,
 117    const enum sort_dir dir)
 118 {
 119         const struct bucket **pa, **pb, **pc, **pd, **pl, **pm, **pn;
 120         int d, r, swap_cnt;
 121
 122 loop:
 123         swap_cnt = 0;
 124         if (n < 7) {
 125                 for (pm = a+1; pm < a+n; pm++)
 126                         for (pl = pm;
 127                              (pl > a) && (cmp(pl-1, pl, dir) > 0);
 128                              pl--)
 129                                 swap(pl, pl-1);
 130                 return;
 131         }
 132         pm = a + (n / 2);
 133         if (n > 7) {
 134                 pl = a;
 135                 pn = a + (n - 1);
 136                 if (n > 40) {
 137                         d = (n / 8);
 138                         pl = med3(pl, pl + d, pl + 2 * d, dir);
 139                         pm = med3(pm - d, pm, pm + d, dir);
 140                         pn = med3(pn - 2 * d, pn - d, pn, dir);
 141                 }
 142                 pm = med3(pl, pm, pn, dir);
 143         }
 144         swap(a, pm);
 145         pa = pb = a + 1;
 146
 147         pc = pd = a + (n - 1);
 148         for (;;) {
 149                 while (pb <= pc && (r = cmp(pb, a, dir)) <= 0) {
 150                         if (r == 0) {
 151                                 swap_cnt = 1;
 152                                 swap(pa, pb);
 153                                 pa++;
 154                         }
 155                         pb++;
 156                 }
 157                 while (pb <= pc && (r = cmp(pc, a, dir)) >= 0) {
 158                         if (r == 0) {
 159                                 swap_cnt = 1;
 160                                 swap(pc, pd);
 161                                 pd--;
 162                         }
 163                         pc--;
 164                 }
 165                 if (pb > pc)
 166                         break;
 167                 swap(pb, pc);
 168                 swap_cnt = 1;
 169                 pb++;
 170                 pc--;
 171         }
 172         if (swap_cnt == 0) {  /* Switch to insertion sort */
 173                 for (pm = a + 1; pm < a+n; pm++)
 174                         for (pl = pm;
 175                              (pl > a) && (cmp(pl-1, pl, dir) > 0);
 176                              pl--)
 177                                 swap(pl, pl-1);
 178                 return;
 179         }
 180
 181         pn = a + n;
 182         r = min(pa - a, pb - pa);
 183         vecswap(a, pb - r, r);
 184         r = min(pd - pc, pn - pd - 1);
 185         vecswap(pb, pn - r, r);
 186         if (((r = pb - pa) > 1) && ((unsigned)r >= left))
 187                 qsort_buckets(a, r, left, right, dir);
 188         if (((r = pd - pc) > 1) && (n - r <= right)) {
 189                 /* Iterate rather than recurse to save stack space */
 190                 if (n - r > left)
 191                         left = 0;
 192                 else
 193                         left -= n - r;
 194                 right -= n - r;
 195                 a += n - r;
 196                 n = r;
 197                 goto loop;
 198         }
 199 /*              qsort(pn - r, r, cmp);*/
 200 }
 201
 202 /* vim:set ts=3 sw=3 tw=78 expandtab: */