FFmpeg: libavutil/integer.c Source File

FFmpeg
integer.c
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1 /*
2  * arbitrary precision integers
3  * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * arbitrary precision integers
25  * @author Michael Niedermayer <michaelni@gmx.at>
26  */
27 
28 #include "common.h"
29 #include "integer.h"
30 #include "avassert.h"
31 
32  AVInteger av_add_i(AVInteger a, AVInteger b){
33  int i, carry=0;
34 
35  for(i=0; i<AV_INTEGER_SIZE; i++){
36  carry= (carry>>16) + a.v[i] + b.v[i];
37  a.v[i]= carry;
38  }
39  return a;
40 }
41 
42  AVInteger av_sub_i(AVInteger a, AVInteger b){
43  int i, carry=0;
44 
45  for(i=0; i<AV_INTEGER_SIZE; i++){
46  carry= (carry>>16) + a.v[i] - b.v[i];
47  a.v[i]= carry;
48  }
49  return a;
50 }
51 
52  int av_log2_i(AVInteger a){
53  int i;
54 
55  for(i=AV_INTEGER_SIZE-1; i>=0; i--){
56  if(a.v[i])
57  return av_log2_16bit(a.v[i]) + 16*i;
58  }
59  return -1;
60 }
61 
62  AVInteger av_mul_i(AVInteger a, AVInteger b){
63  AVInteger out;
64  int i, j;
65  int na= (av_log2_i(a)+16) >> 4;
66  int nb= (av_log2_i(b)+16) >> 4;
67 
68  memset(&out, 0, sizeof(out));
69 
70  for(i=0; i<na; i++){
71  unsigned int carry=0;
72 
73  if(a.v[i])
74  for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
75  carry= (carry>>16) + out.v[j] + a.v[i]*b.v[j-i];
76  out.v[j]= carry;
77  }
78  }
79 
80  return out;
81 }
82 
83  int av_cmp_i(AVInteger a, AVInteger b){
84  int i;
85  int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
86  if(v) return (v>>16)|1;
87 
88  for(i=AV_INTEGER_SIZE-2; i>=0; i--){
89  int v= a.v[i] - b.v[i];
90  if(v) return (v>>16)|1;
91  }
92  return 0;
93 }
94 
95  AVInteger av_shr_i(AVInteger a, int s){
96  AVInteger out;
97  int i;
98 
99  for(i=0; i<AV_INTEGER_SIZE; i++){
100  unsigned int index= i + (s>>4);
101  unsigned int v=0;
102  if(index+1<AV_INTEGER_SIZE) v = a.v[index+1]<<16;
103  if(index <AV_INTEGER_SIZE) v+= a.v[index ];
104  out.v[i]= v >> (s&15);
105  }
106  return out;
107 }
108 
109  AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
110  int i= av_log2_i(a) - av_log2_i(b);
111  AVInteger quot_temp;
112  if(!quot) quot = &quot_temp;
113 
114  av_assert2((int16_t)a.v[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b.v[AV_INTEGER_SIZE-1] >= 0);
115  av_assert2(av_log2_i(b)>=0);
116 
117  if(i > 0)
118  b= av_shr_i(b, -i);
119 
120  memset(quot, 0, sizeof(AVInteger));
121 
122  while(i-- >= 0){
123  *quot= av_shr_i(*quot, -1);
124  if(av_cmp_i(a, b) >= 0){
125  a= av_sub_i(a, b);
126  quot->v[0] += 1;
127  }
128  b= av_shr_i(b, 1);
129  }
130  return a;
131 }
132 
133  AVInteger av_div_i(AVInteger a, AVInteger b){
134  AVInteger quot;
135  av_mod_i(&quot, a, b);
136  return quot;
137 }
138 
139  AVInteger av_int2i(int64_t a){
140  AVInteger out;
141  int i;
142 
143  for(i=0; i<AV_INTEGER_SIZE; i++){
144  out.v[i]= a;
145  a>>=16;
146  }
147  return out;
148 }
149 
150  int64_t av_i2int(AVInteger a){
151  int i;
152  int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
153 
154  for(i= AV_INTEGER_SIZE-2; i>=0; i--){
155  out = (out<<16) + a.v[i];
156  }
157  return out;
158 }
159 
160 #ifdef TEST
161 
162 const uint8_t ff_log2_tab[256]={
163  0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
164  5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
165  6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
166  6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
167  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
168  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
169  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
170  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
171 };
172 
173 int main(void){
174  int64_t a,b;
175 
176  for(a=7; a<256*256*256; a+=13215){
177  for(b=3; b<256*256*256; b+=27118){
178  AVInteger ai= av_int2i(a);
179  AVInteger bi= av_int2i(b);
180 
181  av_assert0(av_i2int(ai) == a);
182  av_assert0(av_i2int(bi) == b);
183  av_assert0(av_i2int(av_add_i(ai,bi)) == a+b);
184  av_assert0(av_i2int(av_sub_i(ai,bi)) == a-b);
185  av_assert0(av_i2int(av_mul_i(ai,bi)) == a*b);
186  av_assert0(av_i2int(av_shr_i(ai, 9)) == a>>9);
187  av_assert0(av_i2int(av_shr_i(ai,-9)) == a<<9);
188  av_assert0(av_i2int(av_shr_i(ai, 17)) == a>>17);
189  av_assert0(av_i2int(av_shr_i(ai,-17)) == a<<17);
190  av_assert0(av_log2_i(ai) == av_log2(a));
191  av_assert0(av_i2int(av_div_i(ai,bi)) == a/b);
192  }
193  }
194  return 0;
195 }
196 #endif
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