lib/qsort.c

   1 /*
   2  * Code adapted from uClibc-0.9.30.3
   3  *
   4  * It is therefore covered by the GNU LESSER GENERAL PUBLIC LICENSE
   5  * Version 2.1, February 1999
   6  *
   7  * Wolfgang Denk <wd@denx.de>
   8  */
   9
  10 /* This code is derived from a public domain shell sort routine by
  11  * Ray Gardner and found in Bob Stout's snippets collection.  The
  12  * original code is included below in an #if 0/#endif block.
  13  *
  14  * I modified it to avoid the possibility of overflow in the wgap
  15  * calculation, as well as to reduce the generated code size with
  16  * bcc and gcc. */
  17
  18 #include <linux/types.h>
  19 #include <exports.h>
  20
  21 void qsort(void  *base,
  22            size_t nel,
  23            size_t width,
  24            int (*comp)(const void *, const void *))
  25 {
  26         size_t wgap, i, j, k;
  27         char tmp;
  28
  29         if ((nel > 1) && (width > 0)) {
  30                 assert(nel <= ((size_t)(-1)) / width); /* check for overflow */
  31                 wgap = 0;
  32                 do {
  33                         wgap = 3 * wgap + 1;
  34                 } while (wgap < (nel-1)/3);
  35                 /* From the above, we know that either wgap == 1 < nel or */
  36                 /* ((wgap-1)/3 < (int) ((nel-1)/3) <= (nel-1)/3 ==> wgap <  nel. */
  37                 wgap *= width;                  /* So this can not overflow if wnel doesn't. */
  38                 nel *= width;                   /* Convert nel to 'wnel' */
  39                 do {
  40                         i = wgap;
  41                         do {
  42                                 j = i;
  43                                 do {
  44                                         register char *a;
  45                                         register char *b;
  46
  47                                         j -= wgap;
  48                                         a = j + ((char *)base);
  49                                         b = a + wgap;
  50                                         if ((*comp)(a, b) <= 0) {
  51                                                 break;
  52                                         }
  53                                         k = width;
  54                                         do {
  55                                                 tmp = *a;
  56                                                 *a++ = *b;
  57                                                 *b++ = tmp;
  58                                         } while (--k);
  59                                 } while (j >= wgap);
  60                                 i += width;
  61                         } while (i < nel);
  62                         wgap = (wgap - width)/3;
  63                 } while (wgap);
  64         }
  65 }
  66
  67 int strcmp_compar(const void *p1, const void *p2)
  68 {
  69         return strcmp(*(const char **)p1, *(const char **)p2);
  70 }