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f87dacb27d
compared to qsort this is slower but its stable and doesnt have a O(n^2) worst case Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
118 lines
4.1 KiB
C
118 lines
4.1 KiB
C
/*
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* copyright (c) 2012 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg 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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*
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* FFmpeg 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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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "common.h"
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/**
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* Quicksort
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* This sort is fast, and fully inplace but not stable and it is possible
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* to construct input that requires O(n^2) time but this is very unlikely to
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* happen with non constructed input.
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*/
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#define AV_QSORT(p, num, type, cmp) {\
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void *stack[64][2];\
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int sp= 1;\
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stack[0][0] = p;\
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stack[0][1] = (p)+(num)-1;\
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while(sp){\
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type *start= stack[--sp][0];\
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type *end = stack[ sp][1];\
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while(start < end){\
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if(start < end-1) {\
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int checksort=0;\
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type *right = end-2;\
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type *left = start+1;\
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type *mid = start + ((end-start)>>1);\
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if(cmp(start, end) < 0) {\
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if(cmp( end, mid) < 0) FFSWAP(type, *start, *mid);\
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else FFSWAP(type, *start, *end);\
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}else{\
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if(cmp(start, mid) < 0) FFSWAP(type, *start, *mid);\
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else checksort= 1;\
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}\
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if(cmp(mid, end) < 0){ \
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FFSWAP(type, *mid, *end);\
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checksort=0;\
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}\
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if(start == end-2) break;\
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FFSWAP(type, end[-1], *mid);\
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while(left <= right){\
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while(left<=right && cmp(left, end-1) > 0)\
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left++;\
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while(left<=right && cmp(right, end-1) < 0)\
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right--;\
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if(left <= right){\
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FFSWAP(type, *left, *right);\
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left++;\
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right--;\
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}\
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}\
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FFSWAP(type, end[-1], *left);\
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if(checksort && (mid == left-1 || mid == left)){\
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mid= start;\
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while(mid<end && cmp(mid, mid+1) >= 0)\
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mid++;\
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if(mid==end)\
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break;\
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}\
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if(end-left < left-start){\
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stack[sp ][0]= start;\
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stack[sp++][1]= right;\
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start = left+1;\
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}else{\
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stack[sp ][0]= left+1;\
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stack[sp++][1]= end;\
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end = right;\
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}\
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}else{\
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if(cmp(start, end) < 0)\
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FFSWAP(type, *start, *end);\
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break;\
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}\
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}\
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}\
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}
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/**
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* Merge sort, this sort requires a temporary buffer and is stable, its worst
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* case time is O(n log n)
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* @param p must be a lvalue pointer, this function may exchange it with tmp
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* @param tmp must be a lvalue pointer, this function may exchange it with p
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*/
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#define AV_MSORT(p, tmp, num, type, cmp) {\
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unsigned i, j, step;\
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for(step=1; step<(num); step+=step){\
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for(i=0; i<(num); i+=2*step){\
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unsigned a[2] = {i, i+step};\
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unsigned end = FFMIN(i+2*step, (num));\
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for(j=i; a[0]<i+step && a[1]<end; j++){\
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int idx= cmp(p+a[0], p+a[1]) < 0;\
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tmp[j] = p[ a[idx]++ ];\
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}\
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if(a[0]>=i+step) a[0] = a[1];\
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for(; j<end; j++){\
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tmp[j] = p[ a[0]++ ];\
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}\
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}\
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FFSWAP(type*, p, tmp);\
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}\
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}
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