* Copyright (c) 1991 The Regents of the University of California.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid
[] = "@(#)heapsort.c 5.1 (Berkeley) 6/4/91";
#endif /* LIBC_SCCS and not lint */
* Swap two areas of size number of bytes. Although qsort(3) permits random
* blocks of memory to be sorted, sorting pointers is almost certainly the
* common case (and, were it not, could easily be made so). Regardless, it
* isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
* arithmetic gets lost in the time required for comparison function calls.
* Build the list into a heap, where a heap is defined such that for
* the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
* There two cases. If j == nmemb, select largest of Ki and Kj. If
* j < nmemb, select largest of Ki, Kj and Kj+1.
* The initial value depends on if we're building the initial heap or
* reconstructing it after saving a value.
#define HEAP(initval) { \
for (i = initval; (j = i * 2) <= nmemb; i = j) { \
p = (char *)bot + j * size; \
if (j < nmemb && compar(p, p + size) < 0) { \
t = (char *)bot + i * size; \
* Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
* and worst. While heapsort is faster than the worst case of quicksort,
* the BSD quicksort does median selection so that the chance of finding
* a data set that will trigger the worst case is nonexistent. Heapsort's
* only advantage over quicksort is that it requires no additional memory.
heapsort(bot
, nmemb
, size
, compar
)
register size_t nmemb
, size
;
int (*compar
) __P((const void *, const void *));
register char *p
, *t
, ch
;
register int cnt
, i
, j
, l
;
* Items are numbered from 1 to nmemb, so offset from size bytes
* below the starting address.
for (l
= nmemb
/ 2 + 1; --l
;)
* For each element of the heap, save the largest element into its
* final slot, then recreate the heap.
t
= (char *)bot
+ nmemb
* size
;