125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/* msort -- an alternative to qsort, with an identical interface.
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This file is part of the GNU C Library.
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Copyright (C) 1992, 1995, 1996, 1997 Free Software Foundation, Inc.
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Written by Mike Haertel, September 1988.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <stdlib.h>
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#include <string.h>
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#include <memcopy.h>
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#include <errno.h>
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static void msort_with_tmp __P ((void *b, size_t n, size_t s,
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__compar_fn_t cmp, char *t));
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static void
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msort_with_tmp (b, n, s, cmp, t)
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void *b;
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size_t n;
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size_t s;
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__compar_fn_t cmp;
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char *t;
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{
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char *tmp;
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char *b1, *b2;
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size_t n1, n2;
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if (n <= 1)
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return;
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n1 = n / 2;
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n2 = n - n1;
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b1 = b;
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b2 = (char *) b + (n1 * s);
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msort_with_tmp (b1, n1, s, cmp, t);
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msort_with_tmp (b2, n2, s, cmp, t);
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tmp = t;
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if (s == OPSIZ && (b1 - (char *) 0) % OPSIZ == 0)
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/* We are operating on aligned words. Use direct word stores. */
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2) <= 0)
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{
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--n1;
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*((op_t *) tmp)++ = *((op_t *) b1)++;
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}
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else
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{
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--n2;
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*((op_t *) tmp)++ = *((op_t *) b2)++;
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}
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}
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else
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2) <= 0)
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{
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memcpy (tmp, b1, s);
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b1 += s;
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--n1;
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}
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else
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{
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memcpy (tmp, b2, s);
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b2 += s;
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--n2;
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}
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tmp += s;
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}
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if (n1 > 0)
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memcpy (tmp, b1, n1 * s);
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memcpy (b, t, (n - n2) * s);
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}
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void
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qsort (b, n, s, cmp)
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void *b;
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size_t n;
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size_t s;
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__compar_fn_t cmp;
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{
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const size_t size = n * s;
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if (size < 1024)
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/* The temporary array is small, so put it on the stack. */
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msort_with_tmp (b, n, s, cmp, __alloca (size));
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else
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{
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/* It's somewhat large, so malloc it. */
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int save = errno;
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char *tmp = malloc (size);
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if (tmp == NULL)
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{
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/* Couldn't get space, so use the slower algorithm
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that doesn't need a temporary array. */
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extern void _quicksort __P ((void *__base,
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size_t __nmemb, size_t __size,
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__compar_fn_t __compar));
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_quicksort (b, n, s, cmp);
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}
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else
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{
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msort_with_tmp (b, n, s, cmp, tmp);
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free (tmp);
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}
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__set_errno (save);
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}
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}
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