fs/yaffs2/yaffs_qsort.c

   1 /*
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * SPDX-License-Identifier:     BSD-3-Clause
   6  */
   7
   8 #include "yportenv.h"
   9 /* #include <linux/string.h> */
  10
  11 /*
  12  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  13  */
  14 #define swapcode(TYPE, parmi, parmj, n) do {            \
  15         long i = (n) / sizeof(TYPE);                    \
  16         register TYPE *pi = (TYPE *) (parmi);           \
  17         register TYPE *pj = (TYPE *) (parmj);           \
  18         do {                                            \
  19                 register TYPE   t = *pi;                \
  20                 *pi++ = *pj;                            \
  21                 *pj++ = t;                              \
  22         } while (--i > 0);                              \
  23 } while (0)
  24
  25 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  26         es % sizeof(long) ? 2 : es == sizeof(long) ? 0 : 1;
  27
  28 static inline void
  29 swapfunc(char *a, char *b, int n, int swaptype)
  30 {
  31         if (swaptype <= 1)
  32                 swapcode(long, a, b, n);
  33         else
  34                 swapcode(char, a, b, n);
  35 }
  36
  37 #define yswap(a, b) do {                                        \
  38         if (swaptype == 0) {                            \
  39                 long t = *(long *)(a);                  \
  40                 *(long *)(a) = *(long *)(b);            \
  41                 *(long *)(b) = t;                       \
  42         } else                                          \
  43                 swapfunc(a, b, es, swaptype);           \
  44 } while (0)
  45
  46 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  47
  48 static inline char *
  49 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
  50 {
  51         return cmp(a, b) < 0 ?
  52                 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a))
  53                 : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c));
  54 }
  55
  56 #ifndef min
  57 #define min(a, b) (((a) < (b)) ? (a) : (b))
  58 #endif
  59
  60 void
  61 yaffs_qsort(void *aa, size_t n, size_t es,
  62         int (*cmp)(const void *, const void *))
  63 {
  64         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  65         int d, r, swaptype, swap_cnt;
  66         register char *a = aa;
  67
  68 loop:   SWAPINIT(a, es);
  69         swap_cnt = 0;
  70         if (n < 7) {
  71                 for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
  72                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
  73                              pl -= es)
  74                                 yswap(pl, pl - es);
  75                 return;
  76         }
  77         pm = (char *)a + (n / 2) * es;
  78         if (n > 7) {
  79                 pl = (char *)a;
  80                 pn = (char *)a + (n - 1) * es;
  81                 if (n > 40) {
  82                         d = (n / 8) * es;
  83                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
  84                         pm = med3(pm - d, pm, pm + d, cmp);
  85                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
  86                 }
  87                 pm = med3(pl, pm, pn, cmp);
  88         }
  89         yswap(a, pm);
  90         pa = pb = (char *)a + es;
  91
  92         pc = pd = (char *)a + (n - 1) * es;
  93         for (;;) {
  94                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
  95                         if (r == 0) {
  96                                 swap_cnt = 1;
  97                                 yswap(pa, pb);
  98                                 pa += es;
  99                         }
 100                         pb += es;
 101                 }
 102                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
 103                         if (r == 0) {
 104                                 swap_cnt = 1;
 105                                 yswap(pc, pd);
 106                                 pd -= es;
 107                         }
 108                         pc -= es;
 109                 }
 110                 if (pb > pc)
 111                         break;
 112                 yswap(pb, pc);
 113                 swap_cnt = 1;
 114                 pb += es;
 115                 pc -= es;
 116         }
 117         if (swap_cnt == 0) {  /* Switch to insertion sort */
 118                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 119                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 120                              pl -= es)
 121                                 yswap(pl, pl - es);
 122                 return;
 123         }
 124
 125         pn = (char *)a + n * es;
 126         r = min(pa - (char *)a, pb - pa);
 127         vecswap(a, pb - r, r);
 128         r = min((long)(pd - pc), (long)(pn - pd - es));
 129         vecswap(pb, pn - r, r);
 130         r = pb - pa;
 131         if (r > es)
 132                 yaffs_qsort(a, r / es, es, cmp);
 133         r = pd - pc;
 134         if (r > es) {
 135                 /* Iterate rather than recurse to save stack space */
 136                 a = pn - r;
 137                 n = r / es;
 138                 goto loop;
 139         }
 140 /*              yaffs_qsort(pn - r, r / es, es, cmp);*/
 141 }