mirror of git://sourceware.org/git/glibc.git
310 lines
6.9 KiB
C
310 lines
6.9 KiB
C
/* 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) 1992-2013 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 Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <alloca.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <memcopy.h>
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#include <errno.h>
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#include <atomic.h>
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struct msort_param
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{
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size_t s;
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size_t var;
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__compar_d_fn_t cmp;
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void *arg;
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char *t;
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};
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static void msort_with_tmp (const struct msort_param *p, void *b, size_t n);
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static void
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msort_with_tmp (const struct msort_param *p, void *b, size_t n)
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{
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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 * p->s);
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msort_with_tmp (p, b1, n1);
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msort_with_tmp (p, b2, n2);
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char *tmp = p->t;
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const size_t s = p->s;
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__compar_d_fn_t cmp = p->cmp;
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void *arg = p->arg;
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switch (p->var)
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{
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case 0:
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2, arg) <= 0)
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{
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*(uint32_t *) tmp = *(uint32_t *) b1;
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b1 += sizeof (uint32_t);
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--n1;
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}
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else
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{
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*(uint32_t *) tmp = *(uint32_t *) b2;
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b2 += sizeof (uint32_t);
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--n2;
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}
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tmp += sizeof (uint32_t);
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}
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break;
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case 1:
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2, arg) <= 0)
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{
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*(uint64_t *) tmp = *(uint64_t *) b1;
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b1 += sizeof (uint64_t);
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--n1;
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}
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else
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{
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*(uint64_t *) tmp = *(uint64_t *) b2;
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b2 += sizeof (uint64_t);
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--n2;
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}
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tmp += sizeof (uint64_t);
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}
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break;
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case 2:
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while (n1 > 0 && n2 > 0)
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{
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unsigned long *tmpl = (unsigned long *) tmp;
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unsigned long *bl;
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tmp += s;
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if ((*cmp) (b1, b2, arg) <= 0)
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{
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bl = (unsigned long *) b1;
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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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bl = (unsigned long *) b2;
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b2 += s;
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--n2;
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}
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while (tmpl < (unsigned long *) tmp)
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*tmpl++ = *bl++;
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}
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break;
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case 3:
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (*(const void **) b1, *(const void **) b2, arg) <= 0)
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{
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*(void **) tmp = *(void **) b1;
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b1 += sizeof (void *);
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--n1;
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}
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else
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{
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*(void **) tmp = *(void **) b2;
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b2 += sizeof (void *);
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--n2;
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}
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tmp += sizeof (void *);
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}
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break;
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default:
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2, arg) <= 0)
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{
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tmp = (char *) __mempcpy (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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tmp = (char *) __mempcpy (tmp, b2, s);
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b2 += s;
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--n2;
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}
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}
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break;
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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, p->t, (n - n2) * s);
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}
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void
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qsort_r (void *b, size_t n, size_t s, __compar_d_fn_t cmp, void *arg)
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{
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size_t size = n * s;
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char *tmp = NULL;
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struct msort_param p;
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/* For large object sizes use indirect sorting. */
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if (s > 32)
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size = 2 * n * sizeof (void *) + 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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p.t = __alloca (size);
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else
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{
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/* We should avoid allocating too much memory since this might
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have to be backed up by swap space. */
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static long int phys_pages;
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static int pagesize;
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if (pagesize == 0)
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{
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phys_pages = __sysconf (_SC_PHYS_PAGES);
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if (phys_pages == -1)
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/* Error while determining the memory size. So let's
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assume there is enough memory. Otherwise the
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implementer should provide a complete implementation of
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the `sysconf' function. */
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phys_pages = (long int) (~0ul >> 1);
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/* The following determines that we will never use more than
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a quarter of the physical memory. */
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phys_pages /= 4;
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/* Make sure phys_pages is written to memory. */
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atomic_write_barrier ();
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pagesize = __sysconf (_SC_PAGESIZE);
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}
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/* Just a comment here. We cannot compute
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phys_pages * pagesize
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and compare the needed amount of memory against this value.
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The problem is that some systems might have more physical
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memory then can be represented with a `size_t' value (when
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measured in bytes. */
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/* If the memory requirements are too high don't allocate memory. */
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if (size / pagesize > (size_t) phys_pages)
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{
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_quicksort (b, n, s, cmp, arg);
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return;
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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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tmp = malloc (size);
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__set_errno (save);
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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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_quicksort (b, n, s, cmp, arg);
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return;
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}
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p.t = tmp;
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}
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p.s = s;
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p.var = 4;
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p.cmp = cmp;
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p.arg = arg;
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if (s > 32)
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{
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/* Indirect sorting. */
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char *ip = (char *) b;
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void **tp = (void **) (p.t + n * sizeof (void *));
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void **t = tp;
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void *tmp_storage = (void *) (tp + n);
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while ((void *) t < tmp_storage)
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{
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*t++ = ip;
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ip += s;
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}
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p.s = sizeof (void *);
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p.var = 3;
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msort_with_tmp (&p, p.t + n * sizeof (void *), n);
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/* tp[0] .. tp[n - 1] is now sorted, copy around entries of
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the original array. Knuth vol. 3 (2nd ed.) exercise 5.2-10. */
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char *kp;
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size_t i;
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for (i = 0, ip = (char *) b; i < n; i++, ip += s)
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if ((kp = tp[i]) != ip)
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{
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size_t j = i;
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char *jp = ip;
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memcpy (tmp_storage, ip, s);
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do
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{
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size_t k = (kp - (char *) b) / s;
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tp[j] = jp;
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memcpy (jp, kp, s);
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j = k;
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jp = kp;
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kp = tp[k];
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}
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while (kp != ip);
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tp[j] = jp;
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memcpy (jp, tmp_storage, s);
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}
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}
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else
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{
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if ((s & (sizeof (uint32_t) - 1)) == 0
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&& ((char *) b - (char *) 0) % __alignof__ (uint32_t) == 0)
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{
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if (s == sizeof (uint32_t))
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p.var = 0;
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else if (s == sizeof (uint64_t)
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&& ((char *) b - (char *) 0) % __alignof__ (uint64_t) == 0)
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p.var = 1;
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else if ((s & (sizeof (unsigned long) - 1)) == 0
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&& ((char *) b - (char *) 0)
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% __alignof__ (unsigned long) == 0)
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p.var = 2;
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}
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msort_with_tmp (&p, b, n);
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}
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free (tmp);
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}
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libc_hidden_def (qsort_r)
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void
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qsort (void *b, size_t n, size_t s, __compar_fn_t cmp)
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{
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return qsort_r (b, n, s, (__compar_d_fn_t) cmp, NULL);
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}
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libc_hidden_def (qsort)
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