1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
/*
* Copyright © 2018, VideoLAN and dav1d authors
* Copyright © 2018, Two Orioles, LLC
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include <limits.h>
#include "common/intops.h"
#include "src/getbits.h"
void dav1d_init_get_bits(GetBits *const c, const uint8_t *const data,
const size_t sz)
{
// If sz were 0, c->eof would need to be initialized to 1.
assert(sz);
c->ptr = c->ptr_start = data;
c->ptr_end = &c->ptr_start[sz];
c->bits_left = 0;
c->state = 0;
c->error = 0;
c->eof = 0;
}
static void refill(GetBits *const c, const unsigned n) {
assert(c->bits_left <= 56);
uint64_t state = 0;
do {
state <<= 8;
c->bits_left += 8;
if (!c->eof)
state |= *c->ptr++;
if (c->ptr >= c->ptr_end) {
c->error = c->eof;
c->eof = 1;
}
} while (n > c->bits_left);
c->state |= state << (64 - c->bits_left);
}
unsigned dav1d_get_bits(GetBits *const c, const unsigned n) {
assert(n <= 32 /* can go up to 57 if we change return type */);
assert(n /* can't shift state by 64 */);
if (n > c->bits_left) refill(c, n);
const uint64_t state = c->state;
c->bits_left -= n;
c->state <<= n;
return (unsigned) (state >> (64 - n));
}
int dav1d_get_sbits(GetBits *const c, const unsigned n) {
const int shift = 31 - n;
const int res = dav1d_get_bits(c, n + 1) << shift;
return res >> shift;
}
unsigned dav1d_get_uleb128(GetBits *const c) {
uint64_t val = 0;
unsigned i = 0, more;
do {
const int v = dav1d_get_bits(c, 8);
more = v & 0x80;
val |= ((uint64_t) (v & 0x7F)) << i;
i += 7;
} while (more && i < 56);
if (val > UINT_MAX || more) {
c->error = 1;
return 0;
}
return (unsigned) val;
}
unsigned dav1d_get_uniform(GetBits *const c, const unsigned max) {
// Output in range [0..max-1]
// max must be > 1, or else nothing is read from the bitstream
assert(max > 1);
const int l = ulog2(max) + 1;
assert(l > 1);
const unsigned m = (1U << l) - max;
const unsigned v = dav1d_get_bits(c, l - 1);
return v < m ? v : (v << 1) - m + dav1d_get_bits(c, 1);
}
unsigned dav1d_get_vlc(GetBits *const c) {
int n_bits = 0;
while (!dav1d_get_bits(c, 1))
if (++n_bits == 32)
return 0xFFFFFFFFU;
return n_bits ? ((1U << n_bits) - 1) + dav1d_get_bits(c, n_bits) : 0;
}
static unsigned get_bits_subexp_u(GetBits *const c, const unsigned ref,
const unsigned n)
{
unsigned v = 0;
for (int i = 0;; i++) {
const int b = i ? 3 + i - 1 : 3;
if (n < v + 3 * (1 << b)) {
v += dav1d_get_uniform(c, n - v + 1);
break;
}
if (!dav1d_get_bits(c, 1)) {
v += dav1d_get_bits(c, b);
break;
}
v += 1 << b;
}
return ref * 2 <= n ? inv_recenter(ref, v) : n - inv_recenter(n - ref, v);
}
int dav1d_get_bits_subexp(GetBits *const c, const int ref, const unsigned n) {
return (int) get_bits_subexp_u(c, ref + (1 << n), 2 << n) - (1 << n);
}
void dav1d_bytealign_get_bits(GetBits *c) {
// bits_left is never more than 7, because it is only incremented
// by refill(), called by dav1d_get_bits and that never reads more
// than 7 bits more than it needs.
//
// If this wasn't true, we would need to work out how many bits to
// discard (bits_left % 8), subtract that from bits_left and then
// shift state right by that amount.
assert(c->bits_left <= 7);
c->bits_left = 0;
c->state = 0;
}
|
