FFmpeg
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
qsort.h
Go to the documentation of this file.
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 #include "common.h"
22 
23 
24 /**
25  * Quicksort
26  * This sort is fast, and fully inplace but not stable and it is possible
27  * to construct input that requires O(n^2) time but this is very unlikely to
28  * happen with non constructed input.
29  */
30 #define AV_QSORT(p, num, type, cmp) {\
31  void *stack[64][2];\
32  int sp= 1;\
33  stack[0][0] = p;\
34  stack[0][1] = (p)+(num)-1;\
35  while(sp){\
36  type *start= stack[--sp][0];\
37  type *end = stack[ sp][1];\
38  while(start < end){\
39  if(start < end-1) {\
40  int checksort=0;\
41  type *right = end-2;\
42  type *left = start+1;\
43  type *mid = start + ((end-start)>>1);\
44  if(cmp(start, end) > 0) {\
45  if(cmp( end, mid) > 0) FFSWAP(type, *start, *mid);\
46  else FFSWAP(type, *start, *end);\
47  }else{\
48  if(cmp(start, mid) > 0) FFSWAP(type, *start, *mid);\
49  else checksort= 1;\
50  }\
51  if(cmp(mid, end) > 0){ \
52  FFSWAP(type, *mid, *end);\
53  checksort=0;\
54  }\
55  if(start == end-2) break;\
56  FFSWAP(type, end[-1], *mid);\
57  while(left <= right){\
58  while(left<=right && cmp(left, end-1) < 0)\
59  left++;\
60  while(left<=right && cmp(right, end-1) > 0)\
61  right--;\
62  if(left <= right){\
63  FFSWAP(type, *left, *right);\
64  left++;\
65  right--;\
66  }\
67  }\
68  FFSWAP(type, end[-1], *left);\
69  if(checksort && (mid == left-1 || mid == left)){\
70  mid= start;\
71  while(mid<end && cmp(mid, mid+1) <= 0)\
72  mid++;\
73  if(mid==end)\
74  break;\
75  }\
76  if(end-left < left-start){\
77  stack[sp ][0]= start;\
78  stack[sp++][1]= right;\
79  start = left+1;\
80  }else{\
81  stack[sp ][0]= left+1;\
82  stack[sp++][1]= end;\
83  end = right;\
84  }\
85  }else{\
86  if(cmp(start, end) > 0)\
87  FFSWAP(type, *start, *end);\
88  break;\
89  }\
90  }\
91  }\
92 }
93 
94 /**
95  * Merge sort, this sort requires a temporary buffer and is stable, its worst
96  * case time is O(n log n)
97  * @param p must be a lvalue pointer, this function may exchange it with tmp
98  * @param tmp must be a lvalue pointer, this function may exchange it with p
99  */
100 #define AV_MSORT(p, tmp, num, type, cmp) {\
101  unsigned i, j, step;\
102  for(step=1; step<(num); step+=step){\
103  for(i=0; i<(num); i+=2*step){\
104  unsigned a[2] = {i, i+step};\
105  unsigned end = FFMIN(i+2*step, (num));\
106  for(j=i; a[0]<i+step && a[1]<end; j++){\
107  int idx= cmp(p+a[0], p+a[1]) > 0;\
108  tmp[j] = p[ a[idx]++ ];\
109  }\
110  if(a[0]>=i+step) a[0] = a[1];\
111  for(; j<end; j++){\
112  tmp[j] = p[ a[0]++ ];\
113  }\
114  }\
115  FFSWAP(type*, p, tmp);\
116  }\
117 }