150 lines
3.6 KiB
C
150 lines
3.6 KiB
C
//
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// qsort.c
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//
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// Quick sort
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//
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// Copyright (C) 2002 Michael Ringgaard. All rights reserved.
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//
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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
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// are met:
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//
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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 the
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// documentation and/or other materials provided with the distribution.
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// 3. Neither the name of the project nor the names of its contributors
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// may be used to endorse or promote products derived from this software
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// without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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// OR 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, STRICT
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// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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//
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#define CUTOFF 8
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static void shortsort(char *lo, char *hi, unsigned width, int (*comp)(const void *, const void *));
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static void swap(char *p, char *q, unsigned int width);
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__attribute__((used))
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void qsort(void *base, unsigned num, unsigned width, int (*comp)(const void *, const void *))
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{
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char *lo, *hi;
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char *mid;
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char *loguy, *higuy;
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unsigned size;
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char *lostk[30], *histk[30];
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int stkptr;
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if (num < 2 || width == 0) return;
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stkptr = 0;
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lo = base;
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hi = (char *) base + width * (num - 1);
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recurse:
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size = (hi - lo) / width + 1;
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if (size <= CUTOFF)
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{
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shortsort(lo, hi, width, comp);
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}
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else
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{
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mid = lo + (size / 2) * width;
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swap(mid, lo, width);
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loguy = lo;
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higuy = hi + width;
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for (;;)
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{
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do { loguy += width; } while (loguy <= hi && comp(loguy, lo) <= 0);
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do { higuy -= width; } while (higuy > lo && comp(higuy, lo) >= 0);
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if (higuy < loguy) break;
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swap(loguy, higuy, width);
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}
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swap(lo, higuy, width);
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if (higuy - 1 - lo >= hi - loguy)
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{
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if (lo + width < higuy)
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{
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lostk[stkptr] = lo;
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histk[stkptr] = higuy - width;
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++stkptr;
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}
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if (loguy < hi)
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{
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lo = loguy;
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goto recurse;
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}
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}
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else
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{
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if (loguy < hi)
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{
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lostk[stkptr] = loguy;
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histk[stkptr] = hi;
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++stkptr;
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}
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if (lo + width < higuy)
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{
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hi = higuy - width;
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goto recurse;
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}
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}
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}
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--stkptr;
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if (stkptr >= 0)
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{
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lo = lostk[stkptr];
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hi = histk[stkptr];
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goto recurse;
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}
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else
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return;
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}
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static void shortsort(char *lo, char *hi, unsigned width, int (*comp)(const void *, const void *))
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{
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char *p, *max;
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while (hi > lo)
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{
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max = lo;
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for (p = lo+width; p <= hi; p += width) if (comp(p, max) > 0) max = p;
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swap(max, hi, width);
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hi -= width;
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}
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}
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static void swap(char *a, char *b, unsigned width)
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{
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char tmp;
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if (a != b)
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{
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while (width--)
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{
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tmp = *a;
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*a++ = *b;
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*b++ = tmp;
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}
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}
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}
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