You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 

99 lines
3.0 KiB

/* qsort -- qsort interface implemented by faster quicksort.
J. L. Bentley and M. D. McIlroy, SPE 23 (1993) 1249-1265.
Copyright 1993, John Wiley.
*/
typedef int cmp_t(const char *, const char *, unsigned int);
/*assume sizeof(long) is a power of 2 */
#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
#define swapcode(TYPE, parmi, parmj, n) { \
register TYPE *pi = (TYPE *) (parmi); \
register TYPE *pj = (TYPE *) (parmj); \
do { \
register TYPE t = *pi; \
*pi++ = *pj; \
*pj++ = t; \
} while ((n -= sizeof(TYPE)) > 0); \
}
#include <stddef.h>
static void swapfunc(char *a, char *b, size_t n, int swaptype)
{ if (swaptype <= 1) swapcode(long, a, b, n)
else swapcode(char, a, b, n)
}
#define swap(a, b) \
if (swaptype == 0) { \
t = *(long*)(a); \
*(long*)(a) = *(long*)(b); \
*(long*)(b) = t; \
} else \
swapfunc(a, b, es, swaptype)
#define vecswap(a, b, n) if (n > 0) swapfunc(a, b, n, swaptype)
#ifndef min
#define min(x, y) ((x)<=(y) ? (x) : (y))
#endif
static char *med3(char *a, char *b, char *c, cmp_t *cmp, unsigned int flag)
{ return cmp(a, b, flag) < 0 ?
(cmp(b, c, flag) < 0 ? b : cmp(a, c, flag) < 0 ? c : a)
: (cmp(b, c, flag) > 0 ? b : cmp(a, c, flag) > 0 ? c : a);
}
void quicksort(char *a, size_t n, size_t es, cmp_t *cmp, unsigned flag)
{
char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
int r, swaptype;
long t;
size_t s;
loop: SWAPINIT(a, es);
if (n < 7) { /* Insertion sort on smallest arrays */
for (pm = a + es; pm < a + n*es; pm += es)
for (pl = pm; pl > a && cmp(pl-es, pl, flag) > 0; pl -= es)
swap(pl, pl-es);
return;
}
pm = a + (n/2)*es; /* Small arrays, middle element */
if (n > 7) {
pl = a;
pn = a + (n-1)*es;
if (n > 40) { /* Big arrays, pseudomedian of 9 */
s = (n/8)*es;
pl = med3(pl, pl+s, pl+2*s, cmp, flag);
pm = med3(pm-s, pm, pm+s, cmp, flag);
pn = med3(pn-2*s, pn-s, pn, cmp, flag);
}
pm = med3(pl, pm, pn, cmp, flag); /* Mid-size, med of 3 */
}
swap(a, pm);
pa = pb = a + es;
pc = pd = a + (n-1)*es;
for (;;) {
while (pb <= pc && (r = cmp(pb, a, flag)) <= 0) {
if (r == 0) { swap(pa, pb); pa += es; }
pb += es;
}
while (pb <= pc && (r = cmp(pc, a, flag)) >= 0) {
if (r == 0) { swap(pc, pd); pd -= es; }
pc -= es;
}
if (pb > pc) break;
swap(pb, pc);
pb += es;
pc -= es;
}
pn = a + n*es;
s = min(pa-a, pb-pa ); vecswap(a, pb-s, s);
s = min(pd-pc, pn-pd-(long)es); vecswap(pb, pn-s, s);
if ((s = pb-pa) > es) quicksort(a, s/es, es, cmp, flag);
if ((s = pd-pc) > es) {
/* Iterate rather than recurse to save stack space */
a = pn - s;
n = s / es;
goto loop;
}
/* quicksort(pn-s, s/es, es, cmp, flag); */
}