157 lines
3.7 KiB
C
157 lines
3.7 KiB
C
/* Sort a vector of pointers to data.
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Copyright (C) 2007, 2009-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Paul Eggert. */
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#include <config.h>
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#include "mpsort.h"
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#include <string.h>
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/* The type of qsort-style comparison functions. */
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typedef int (*comparison_function) (void const *, void const *);
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static void mpsort_with_tmp (void const **restrict, size_t,
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void const **restrict, comparison_function);
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/* Sort a vector BASE containing N pointers, placing the sorted array
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into TMP. Compare pointers with CMP. N must be at least 2. */
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static void
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mpsort_into_tmp (void const **restrict base, size_t n,
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void const **restrict tmp,
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comparison_function cmp)
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{
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size_t n1 = n / 2;
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size_t n2 = n - n1;
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size_t a = 0;
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size_t alim = n1;
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size_t b = n1;
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size_t blim = n;
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void const *ba;
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void const *bb;
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mpsort_with_tmp (base + n1, n2, tmp, cmp);
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mpsort_with_tmp (base, n1, tmp, cmp);
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ba = base[a];
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bb = base[b];
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for (;;)
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if (cmp (ba, bb) <= 0)
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{
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*tmp++ = ba;
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a++;
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if (a == alim)
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{
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a = b;
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alim = blim;
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break;
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}
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ba = base[a];
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}
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else
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{
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*tmp++ = bb;
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b++;
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if (b == blim)
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break;
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bb = base[b];
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}
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memcpy (tmp, base + a, (alim - a) * sizeof *base);
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}
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/* Sort a vector BASE containing N pointers, in place. Use TMP
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(containing N / 2 pointers) for temporary storage. Compare
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pointers with CMP. */
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static void
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mpsort_with_tmp (void const **restrict base, size_t n,
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void const **restrict tmp,
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comparison_function cmp)
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{
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if (n <= 2)
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{
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if (n == 2)
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{
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void const *p0 = base[0];
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void const *p1 = base[1];
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if (! (cmp (p0, p1) <= 0))
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{
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base[0] = p1;
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base[1] = p0;
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}
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}
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}
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else
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{
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size_t n1 = n / 2;
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size_t n2 = n - n1;
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size_t i;
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size_t t = 0;
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size_t tlim = n1;
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size_t b = n1;
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size_t blim = n;
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void const *bb;
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void const *tt;
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mpsort_with_tmp (base + n1, n2, tmp, cmp);
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if (n1 < 2)
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tmp[0] = base[0];
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else
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mpsort_into_tmp (base, n1, tmp, cmp);
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tt = tmp[t];
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bb = base[b];
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for (i = 0; ; )
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if (cmp (tt, bb) <= 0)
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{
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base[i++] = tt;
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t++;
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if (t == tlim)
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break;
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tt = tmp[t];
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}
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else
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{
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base[i++] = bb;
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b++;
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if (b == blim)
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{
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memcpy (base + i, tmp + t, (tlim - t) * sizeof *base);
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break;
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}
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bb = base[b];
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}
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}
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}
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/* Sort a vector BASE containing N pointers, in place. BASE must
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contain enough storage to hold N + N / 2 vectors; the trailing
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vectors are used for temporaries. Compare pointers with CMP. */
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void
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mpsort (void const **base, size_t n, comparison_function cmp)
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{
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mpsort_with_tmp (base, n, base + n, cmp);
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}
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