intmath.h
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1 /*
2  * Copyright (c) 2010 Mans Rullgard <mans@mansr.com>
3  *
4  * This file is part of Libav.
5  *
6  * Libav 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  * Libav 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 Libav; 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_INTMATH_H
22 #define AVUTIL_INTMATH_H
23 
24 #include <stdint.h>
25 #include "config.h"
26 #include "attributes.h"
27 
33 extern const uint32_t ff_inverse[257];
34 
35 #if ARCH_ARM
36 # include "arm/intmath.h"
37 #elif ARCH_X86
38 # include "x86/intmath.h"
39 #endif
40 
41 #if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)
42 
43 #ifndef av_log2
44 # define av_log2(x) (31 - __builtin_clz((x)|1))
45 # ifndef av_log2_16bit
46 # define av_log2_16bit av_log2
47 # endif
48 #endif /* av_log2 */
49 
50 #endif /* AV_GCC_VERSION_AT_LEAST(3,4) */
51 
52 #ifndef FASTDIV
53 # if CONFIG_FASTDIV
54 # define FASTDIV(a,b) ((uint32_t)((((uint64_t)a) * ff_inverse[b]) >> 32))
55 # else
56 # define FASTDIV(a,b) ((a) / (b))
57 # endif
58 #endif /* FASTDIV */
59 
60 #include "common.h"
61 
62 extern const uint8_t ff_sqrt_tab[256];
63 
64 static inline av_const unsigned int ff_sqrt(unsigned int a)
65 {
66  unsigned int b;
67 
68  if (a < 255) return (ff_sqrt_tab[a + 1] - 1) >> 4;
69  else if (a < (1 << 12)) b = ff_sqrt_tab[a >> 4] >> 2;
70 #if !CONFIG_SMALL
71  else if (a < (1 << 14)) b = ff_sqrt_tab[a >> 6] >> 1;
72  else if (a < (1 << 16)) b = ff_sqrt_tab[a >> 8] ;
73 #endif
74  else {
75  int s = av_log2_16bit(a >> 16) >> 1;
76  unsigned int c = a >> (s + 2);
77  b = ff_sqrt_tab[c >> (s + 8)];
78  b = FASTDIV(c,b) + (b << s);
79  }
80 
81  return b - (a < b * b);
82 }
83 
87 #endif /* AVUTIL_INTMATH_H */