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/* Sort a vector of pointers to data.
Copyright (C) 2007, 2009-2023 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <config.h>
#include "mpsort.h"
#include <string.h>
/* The type of qsort-style comparison functions. */
typedef int (*comparison_function) (void const *, void const *);
static void mpsort_with_tmp (void const **restrict, size_t,
void const **restrict, comparison_function);
/* Sort a vector BASE containing N pointers, placing the sorted array
into TMP. Compare pointers with CMP. N must be at least 2. */
static void
mpsort_into_tmp (void const **restrict base, size_t n,
void const **restrict tmp,
comparison_function cmp)
{
size_t n1 = n / 2;
size_t n2 = n - n1;
size_t a = 0;
size_t alim = n1;
size_t b = n1;
size_t blim = n;
void const *ba;
void const *bb;
mpsort_with_tmp (base + n1, n2, tmp, cmp);
mpsort_with_tmp (base, n1, tmp, cmp);
ba = base[a];
bb = base[b];
for (;;)
if (cmp (ba, bb) <= 0)
{
*tmp++ = ba;
a++;
if (a == alim)
{
a = b;
alim = blim;
break;
}
ba = base[a];
}
else
{
*tmp++ = bb;
b++;
if (b == blim)
break;
bb = base[b];
}
memcpy (tmp, base + a, (alim - a) * sizeof *base);
}
/* Sort a vector BASE containing N pointers, in place. Use TMP
(containing N / 2 pointers) for temporary storage. Compare
pointers with CMP. */
static void
mpsort_with_tmp (void const **restrict base, size_t n,
void const **restrict tmp,
comparison_function cmp)
{
if (n <= 2)
{
if (n == 2)
{
void const *p0 = base[0];
void const *p1 = base[1];
if (! (cmp (p0, p1) <= 0))
{
base[0] = p1;
base[1] = p0;
}
}
}
else
{
size_t n1 = n / 2;
size_t n2 = n - n1;
size_t i;
size_t t = 0;
size_t tlim = n1;
size_t b = n1;
size_t blim = n;
void const *bb;
void const *tt;
mpsort_with_tmp (base + n1, n2, tmp, cmp);
if (n1 < 2)
tmp[0] = base[0];
else
mpsort_into_tmp (base, n1, tmp, cmp);
tt = tmp[t];
bb = base[b];
for (i = 0; ; )
if (cmp (tt, bb) <= 0)
{
base[i++] = tt;
t++;
if (t == tlim)
break;
tt = tmp[t];
}
else
{
base[i++] = bb;
b++;
if (b == blim)
{
memcpy (base + i, tmp + t, (tlim - t) * sizeof *base);
break;
}
bb = base[b];
}
}
}
/* Sort a vector BASE containing N pointers, in place. BASE must
contain enough storage to hold N + N / 2 vectors; the trailing
vectors are used for temporaries. Compare pointers with CMP. */
void
mpsort (void const **base, size_t n, comparison_function cmp)
{
mpsort_with_tmp (base, n, base + n, cmp);
}
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