/
mergesort.c
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/
mergesort.c
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/*
* mergesort() implementation for systems that don't have it.
*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Peter McIlroy.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 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. 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
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "util.h"
/*@unused@*/ RCSID("$Id$");
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)merge.c 8.2 (Berkeley) 2/14/94";
#endif /* LIBC_SCCS and not lint */
#ifdef HAVE_MERGESORT
#undef yasm__mergesort
#endif
#ifndef HAVE_MERGESORT
/*
* Hybrid exponential search/linear search merge sort with hybrid
* natural/pairwise first pass. Requires about .3% more comparisons
* for random data than LSMS with pairwise first pass alone.
* It works for objects as small as two bytes.
*/
#define NATURAL
#define THRESHOLD 16 /* Best choice for natural merge cut-off. */
/* #define NATURAL to get hybrid natural merge.
* (The default is pairwise merging.)
*/
#include <errno.h>
#include <string.h>
static void setup(unsigned char *, unsigned char *, size_t, size_t,
int (*)(const void *, const void *));
static void insertionsort(unsigned char *, size_t, size_t,
int (*)(const void *, const void *));
#define ISIZE sizeof(int)
#define PSIZE sizeof(unsigned char *)
#define ICOPY_LIST(src, dst, last) \
do \
*(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
while(src < last)
#define ICOPY_ELT(src, dst, i) \
do \
*(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
while (i -= ISIZE)
#define CCOPY_LIST(src, dst, last) \
do \
*dst++ = *src++; \
while (src < last)
#define CCOPY_ELT(src, dst, i) \
do \
*dst++ = *src++; \
while (i -= 1)
/*
* Find the next possible pointer head. (Trickery for forcing an array
* to do double duty as a linked list when objects do not align with word
* boundaries.
*/
/* Assumption: PSIZE is a power of 2. */
#define EVAL(p) (unsigned char **) \
((unsigned char *)0 + \
(((unsigned char *)p + PSIZE - 1 - (unsigned char *) 0) & ~(PSIZE - 1)))
#endif /*HAVE_MERGESORT*/
/*
* Arguments are as for qsort.
*/
int
yasm__mergesort(void *base, size_t nmemb, size_t size,
int (*cmp)(const void *, const void *))
{
#ifdef HAVE_MERGESORT
return mergesort(base, nmemb, size, cmp);
#else
size_t i;
int sense;
int big, iflag;
unsigned char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
unsigned char *list2, *list1, *p2, *p, *last, **p1;
if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
#ifdef EINVAL
errno = EINVAL;
#endif
return (-1);
}
if (nmemb == 0)
return (0);
/*
* XXX
* Stupid subtraction for the Cray.
*/
iflag = 0;
if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
iflag = 1;
if ((list2 = yasm_xmalloc(nmemb * size + PSIZE)) == NULL)
return (-1);
list1 = base;
setup(list1, list2, nmemb, size, cmp);
last = list2 + nmemb * size;
i = 0;
big = 0;
while (*EVAL(list2) != last) {
l2 = list1;
p1 = EVAL(list1);
for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
p2 = *EVAL(p2);
f1 = l2;
f2 = l1 = list1 + (p2 - list2);
if (p2 != last)
p2 = *EVAL(p2);
l2 = list1 + (p2 - list2);
while (f1 < l1 && f2 < l2) {
if ((*cmp)(f1, f2) <= 0) {
q = f2;
b = f1, t = l1;
sense = -1;
} else {
q = f1;
b = f2, t = l2;
sense = 0;
}
if (!big) { /* here i = 0 */
while ((b += size) < t && cmp(q, b) >sense)
if (++i == 6) {
big = 1;
goto EXPONENTIAL;
}
} else {
EXPONENTIAL: for (i = size; ; i <<= 1)
if ((p = (b + i)) >= t) {
if ((p = t - size) > b &&
(*cmp)(q, p) <= sense)
t = p;
else
b = p;
break;
} else if ((*cmp)(q, p) <= sense) {
t = p;
if (i == size)
big = 0;
goto FASTCASE;
} else
b = p;
while (t > b+size) {
i = (((t - b) / size) >> 1) * size;
if ((*cmp)(q, p = b + i) <= sense)
t = p;
else
b = p;
}
goto COPY;
FASTCASE: while (i > size)
if ((*cmp)(q,
p = b + (i >>= 1)) <= sense)
t = p;
else
b = p;
COPY: b = t;
}
i = size;
if (q == f1) {
if (iflag) {
ICOPY_LIST(f2, tp2, b);
ICOPY_ELT(f1, tp2, i);
} else {
CCOPY_LIST(f2, tp2, b);
CCOPY_ELT(f1, tp2, i);
}
} else {
if (iflag) {
ICOPY_LIST(f1, tp2, b);
ICOPY_ELT(f2, tp2, i);
} else {
CCOPY_LIST(f1, tp2, b);
CCOPY_ELT(f2, tp2, i);
}
}
}
if (f2 < l2) {
if (iflag)
ICOPY_LIST(f2, tp2, l2);
else
CCOPY_LIST(f2, tp2, l2);
} else if (f1 < l1) {
if (iflag)
ICOPY_LIST(f1, tp2, l1);
else
CCOPY_LIST(f1, tp2, l1);
}
*p1 = l2;
}
tp2 = list1; /* swap list1, list2 */
list1 = list2;
list2 = tp2;
last = list2 + nmemb*size;
}
if (base == list2) {
memmove(list2, list1, nmemb*size);
list2 = list1;
}
yasm_xfree(list2);
return (0);
#endif /*HAVE_MERGESORT*/
}
#ifndef HAVE_MERGESORT
#define swap(a, b) { \
s = b; \
i = size; \
do { \
tmp = *a; *a++ = *s; *s++ = tmp; \
} while (--i); \
a -= size; \
}
#define reverse(bot, top) { \
s = top; \
do { \
i = size; \
do { \
tmp = *bot; *bot++ = *s; *s++ = tmp; \
} while (--i); \
s -= size2; \
} while(bot < s); \
}
/*
* Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
* increasing order, list2 in a corresponding linked list. Checks for runs
* when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
* is defined. Otherwise simple pairwise merging is used.)
*/
void
setup(unsigned char *list1, unsigned char *list2, size_t n, size_t size,
int (*cmp)(const void *, const void *))
{
size_t i;
unsigned int tmp;
int length, sense;
size_t size2;
unsigned char *f1, *f2, *s, *l2, *last, *p2;
size2 = size*2;
if (n <= 5) {
insertionsort(list1, n, size, cmp);
*EVAL(list2) = (unsigned char*) list2 + n*size;
return;
}
/*
* Avoid running pointers out of bounds; limit n to evens
* for simplicity.
*/
i = 4 + (n & 1);
insertionsort(list1 + (n - i) * size, i, size, cmp);
last = list1 + size * (n - i);
*EVAL(list2 + (last - list1)) = list2 + n * size;
#ifdef NATURAL
p2 = list2;
f1 = list1;
sense = (cmp(f1, f1 + size) > 0);
for (; f1 < last; sense = !sense) {
length = 2;
/* Find pairs with same sense. */
for (f2 = f1 + size2; f2 < last; f2 += size2) {
if ((cmp(f2, f2+ size) > 0) != sense)
break;
length += 2;
}
if (length < THRESHOLD) { /* Pairwise merge */
do {
p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
if (sense > 0)
swap (f1, f1 + size);
} while ((f1 += size2) < f2);
} else { /* Natural merge */
l2 = f2;
for (f2 = f1 + size2; f2 < l2; f2 += size2) {
if ((cmp(f2-size, f2) > 0) != sense) {
p2 = *EVAL(p2) = f2 - list1 + list2;
if (sense > 0)
reverse(f1, f2-size);
f1 = f2;
}
}
if (sense > 0)
reverse (f1, f2-size);
f1 = f2;
if (f2 < last || cmp(f2 - size, f2) > 0)
p2 = *EVAL(p2) = f2 - list1 + list2;
else
p2 = *EVAL(p2) = list2 + n*size;
}
}
#else /* pairwise merge only. */
for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
p2 = *EVAL(p2) = p2 + size2;
if (cmp (f1, f1 + size) > 0)
swap(f1, f1 + size);
}
#endif /* NATURAL */
}
/*
* This is to avoid out-of-bounds addresses in sorting the
* last 4 elements.
*/
static void
insertionsort(unsigned char *a, size_t n, size_t size,
int (*cmp)(const void *, const void *))
{
unsigned char *ai, *s, *t, *u, tmp;
size_t i;
for (ai = a+size; --n >= 1; ai += size)
for (t = ai; t > a; t -= size) {
u = t - size;
if (cmp(u, t) <= 0)
break;
swap(u, t);
}
}
#endif /*HAVE_MERGESORT*/