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1 /*
2  * Copyright (c) 2016, Alliance for Open Media. All rights reserved
3  *
4  * This source code is subject to the terms of the BSD 2 Clause License and
5  * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
6  * was not distributed with this source code in the LICENSE file, you can
7  * obtain it at www.aomedia.org/license/software. If the Alliance for Open
8  * Media Patent License 1.0 was not distributed with this source code in the
9  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
10  */
11 
12 #include <assert.h>
13 
14 #include "config/aom_config.h"
15 
16 #include "aom_dsp/bitreader_buffer.h"
17 #include "aom_dsp/recenter.h"
18 #include "aom_ports/bitops.h"
19 
aom_rb_bytes_read(const struct aom_read_bit_buffer * rb)20 size_t aom_rb_bytes_read(const struct aom_read_bit_buffer *rb) {
21   return (rb->bit_offset + 7) >> 3;
22 }
23 
aom_rb_read_bit(struct aom_read_bit_buffer * rb)24 int aom_rb_read_bit(struct aom_read_bit_buffer *rb) {
25   const uint32_t off = rb->bit_offset;
26   const uint32_t p = off >> 3;
27   const int q = 7 - (int)(off & 0x7);
28   if (rb->bit_buffer + p < rb->bit_buffer_end) {
29     const int bit = (rb->bit_buffer[p] >> q) & 1;
30     rb->bit_offset = off + 1;
31     return bit;
32   } else {
33     if (rb->error_handler) rb->error_handler(rb->error_handler_data);
34     return 0;
35   }
36 }
37 
aom_rb_read_literal(struct aom_read_bit_buffer * rb,int bits)38 int aom_rb_read_literal(struct aom_read_bit_buffer *rb, int bits) {
39   assert(bits <= 31);
40   int value = 0, bit;
41   for (bit = bits - 1; bit >= 0; bit--) value |= aom_rb_read_bit(rb) << bit;
42   return value;
43 }
44 
aom_rb_read_unsigned_literal(struct aom_read_bit_buffer * rb,int bits)45 uint32_t aom_rb_read_unsigned_literal(struct aom_read_bit_buffer *rb,
46                                       int bits) {
47   assert(bits <= 32);
48   uint32_t value = 0;
49   int bit;
50   for (bit = bits - 1; bit >= 0; bit--)
51     value |= (uint32_t)aom_rb_read_bit(rb) << bit;
52   return value;
53 }
54 
aom_rb_read_inv_signed_literal(struct aom_read_bit_buffer * rb,int bits)55 int aom_rb_read_inv_signed_literal(struct aom_read_bit_buffer *rb, int bits) {
56   const int nbits = sizeof(unsigned) * 8 - bits - 1;
57   const unsigned value = (unsigned)aom_rb_read_literal(rb, bits + 1) << nbits;
58   return ((int)value) >> nbits;
59 }
60 
aom_rb_read_uvlc(struct aom_read_bit_buffer * rb)61 uint32_t aom_rb_read_uvlc(struct aom_read_bit_buffer *rb) {
62   int leading_zeros = 0;
63   while (leading_zeros < 32 && !aom_rb_read_bit(rb)) ++leading_zeros;
64   // Maximum 32 bits.
65   if (leading_zeros == 32) return UINT32_MAX;
66   const uint32_t base = (1u << leading_zeros) - 1;
67   const uint32_t value = aom_rb_read_literal(rb, leading_zeros);
68   return base + value;
69 }
70 
aom_rb_read_primitive_quniform(struct aom_read_bit_buffer * rb,uint16_t n)71 static uint16_t aom_rb_read_primitive_quniform(struct aom_read_bit_buffer *rb,
72                                                uint16_t n) {
73   if (n <= 1) return 0;
74   const int l = get_msb(n) + 1;
75   const int m = (1 << l) - n;
76   const int v = aom_rb_read_literal(rb, l - 1);
77   return v < m ? v : (v << 1) - m + aom_rb_read_bit(rb);
78 }
79 
aom_rb_read_primitive_subexpfin(struct aom_read_bit_buffer * rb,uint16_t n,uint16_t k)80 static uint16_t aom_rb_read_primitive_subexpfin(struct aom_read_bit_buffer *rb,
81                                                 uint16_t n, uint16_t k) {
82   int i = 0;
83   int mk = 0;
84 
85   while (1) {
86     int b = (i ? k + i - 1 : k);
87     int a = (1 << b);
88 
89     if (n <= mk + 3 * a) {
90       return aom_rb_read_primitive_quniform(rb, n - mk) + mk;
91     }
92 
93     if (!aom_rb_read_bit(rb)) {
94       return aom_rb_read_literal(rb, b) + mk;
95     }
96 
97     i = i + 1;
98     mk += a;
99   }
100 
101   assert(0);
102   return 0;
103 }
104 
aom_rb_read_primitive_refsubexpfin(struct aom_read_bit_buffer * rb,uint16_t n,uint16_t k,uint16_t ref)105 static uint16_t aom_rb_read_primitive_refsubexpfin(
106     struct aom_read_bit_buffer *rb, uint16_t n, uint16_t k, uint16_t ref) {
107   return inv_recenter_finite_nonneg(n, ref,
108                                     aom_rb_read_primitive_subexpfin(rb, n, k));
109 }
110 
aom_rb_read_signed_primitive_refsubexpfin(struct aom_read_bit_buffer * rb,uint16_t n,uint16_t k,int16_t ref)111 int16_t aom_rb_read_signed_primitive_refsubexpfin(
112     struct aom_read_bit_buffer *rb, uint16_t n, uint16_t k, int16_t ref) {
113   ref += n - 1;
114   const uint16_t scaled_n = (n << 1) - 1;
115   return aom_rb_read_primitive_refsubexpfin(rb, scaled_n, k, ref) - n + 1;
116 }
117