FFmpeg
qsort.h
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1 /*
2  * copyright (c) 2012 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #ifndef AVUTIL_QSORT_H
22 #define AVUTIL_QSORT_H
23 
24 #include "common.h"
25 
26 
27 /**
28  * Quicksort
29  * This sort is fast, and fully inplace but not stable and it is possible
30  * to construct input that requires O(n^2) time but this is very unlikely to
31  * happen with non constructed input.
32  */
33 #define AV_QSORT(p, num, type, cmp) do {\
34  void *stack[64][2];\
35  int sp= 1;\
36  stack[0][0] = p;\
37  stack[0][1] = (p)+(num)-1;\
38  while(sp){\
39  type *start= stack[--sp][0];\
40  type *end = stack[ sp][1];\
41  while(start < end){\
42  if(start < end-1) {\
43  int checksort=0;\
44  type *right = end-2;\
45  type *left = start+1;\
46  type *mid = start + ((end-start)>>1);\
47  if(cmp(start, end) > 0) {\
48  if(cmp( end, mid) > 0) FFSWAP(type, *start, *mid);\
49  else FFSWAP(type, *start, *end);\
50  }else{\
51  if(cmp(start, mid) > 0) FFSWAP(type, *start, *mid);\
52  else checksort= 1;\
53  }\
54  if(cmp(mid, end) > 0){ \
55  FFSWAP(type, *mid, *end);\
56  checksort=0;\
57  }\
58  if(start == end-2) break;\
59  FFSWAP(type, end[-1], *mid);\
60  while(left <= right){\
61  while(left<=right && cmp(left, end-1) < 0)\
62  left++;\
63  while(left<=right && cmp(right, end-1) > 0)\
64  right--;\
65  if(left <= right){\
66  FFSWAP(type, *left, *right);\
67  left++;\
68  right--;\
69  }\
70  }\
71  FFSWAP(type, end[-1], *left);\
72  if(checksort && (mid == left-1 || mid == left)){\
73  mid= start;\
74  while(mid<end && cmp(mid, mid+1) <= 0)\
75  mid++;\
76  if(mid==end)\
77  break;\
78  }\
79  if(end-left < left-start){\
80  stack[sp ][0]= start;\
81  stack[sp++][1]= right;\
82  start = left+1;\
83  }else{\
84  stack[sp ][0]= left+1;\
85  stack[sp++][1]= end;\
86  end = right;\
87  }\
88  }else{\
89  if(cmp(start, end) > 0)\
90  FFSWAP(type, *start, *end);\
91  break;\
92  }\
93  }\
94  }\
95 } while (0)
96 
97 /**
98  * Merge sort, this sort requires a temporary buffer and is stable, its worst
99  * case time is O(n log n)
100  * @param p must be a lvalue pointer, this function may exchange it with tmp
101  * @param tmp must be a lvalue pointer, this function may exchange it with p
102  */
103 #define AV_MSORT(p, tmp, num, type, cmp) do {\
104  unsigned i, j, step;\
105  for(step=1; step<(num); step+=step){\
106  for(i=0; i<(num); i+=2*step){\
107  unsigned a[2] = {i, i+step};\
108  unsigned end = FFMIN(i+2*step, (num));\
109  for(j=i; a[0]<i+step && a[1]<end; j++){\
110  int idx= cmp(p+a[0], p+a[1]) > 0;\
111  tmp[j] = p[ a[idx]++ ];\
112  }\
113  if(a[0]>=i+step) a[0] = a[1];\
114  for(; j<end; j++){\
115  tmp[j] = p[ a[0]++ ];\
116  }\
117  }\
118  FFSWAP(type*, p, tmp);\
119  }\
120 } while (0)
121 
122 #endif /* AVUTIL_QSORT_H */
common internal and external API header