109 lines
3.1 KiB
C
109 lines
3.1 KiB
C
/* sort.c -- Sort without allocating memory
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Copyright (C) 2012-2020 Free Software Foundation, Inc.
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Written by Ian Lance Taylor, Google.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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(1) Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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(2) Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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(3) The name of the author may not be used to
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endorse or promote products derived from this software without
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specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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#include "config.h"
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#include <stddef.h>
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#include <sys/types.h>
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#include "backtrace.h"
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#include "internal.h"
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/* The GNU glibc version of qsort allocates memory, which we must not
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do if we are invoked by a signal handler. So provide our own
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sort. */
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static void
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swap (char *a, char *b, size_t size)
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{
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size_t i;
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for (i = 0; i < size; i++, a++, b++)
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{
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char t;
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t = *a;
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*a = *b;
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*b = t;
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}
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}
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void
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backtrace_qsort (void *basearg, size_t count, size_t size,
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int (*compar) (const void *, const void *))
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{
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char *base = (char *) basearg;
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size_t i;
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size_t mid;
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tail_recurse:
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if (count < 2)
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return;
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/* The symbol table and DWARF tables, which is all we use this
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routine for, tend to be roughly sorted. Pick the middle element
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in the array as our pivot point, so that we are more likely to
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cut the array in half for each recursion step. */
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swap (base, base + (count / 2) * size, size);
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mid = 0;
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for (i = 1; i < count; i++)
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{
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if ((*compar) (base, base + i * size) > 0)
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{
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++mid;
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if (i != mid)
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swap (base + mid * size, base + i * size, size);
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}
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}
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if (mid > 0)
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swap (base, base + mid * size, size);
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/* Recurse with the smaller array, loop with the larger one. That
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ensures that our maximum stack depth is log count. */
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if (2 * mid < count)
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{
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backtrace_qsort (base, mid, size, compar);
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base += (mid + 1) * size;
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count -= mid + 1;
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goto tail_recurse;
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}
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else
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{
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backtrace_qsort (base + (mid + 1) * size, count - (mid + 1),
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size, compar);
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count = mid;
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goto tail_recurse;
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}
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}
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