1 /*
2 * Copyright (c) 2017, 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 "aom_dsp/binary_codes_reader.h"
13 #include "aom_dsp/recenter.h"
14
15 #define read_primitive_quniform(r, n, ACCT_STR_NAME) \
16 read_primitive_quniform_(r, n ACCT_STR_ARG(ACCT_STR_NAME))
17 #define read_primitive_subexpfin(r, n, k, ACCT_STR_NAME) \
18 read_primitive_subexpfin_(r, n, k ACCT_STR_ARG(ACCT_STR_NAME))
19
read_primitive_quniform_(aom_reader * r,uint16_t n ACCT_STR_PARAM)20 static uint16_t read_primitive_quniform_(aom_reader *r,
21 uint16_t n ACCT_STR_PARAM) {
22 if (n <= 1) return 0;
23 const int l = get_msb(n) + 1;
24 const int m = (1 << l) - n;
25 const int v = aom_read_literal(r, l - 1, ACCT_STR_NAME);
26 return v < m ? v : (v << 1) - m + aom_read_bit(r, ACCT_STR_NAME);
27 }
28
29 // Decode finite subexponential code that for a symbol v in [0, n-1] with
30 // parameter k
read_primitive_subexpfin_(aom_reader * r,uint16_t n,uint16_t k ACCT_STR_PARAM)31 static uint16_t read_primitive_subexpfin_(aom_reader *r, uint16_t n,
32 uint16_t k ACCT_STR_PARAM) {
33 int i = 0;
34 int mk = 0;
35
36 while (1) {
37 int b = (i ? k + i - 1 : k);
38 int a = (1 << b);
39
40 if (n <= mk + 3 * a) {
41 return read_primitive_quniform(r, n - mk, ACCT_STR_NAME) + mk;
42 }
43
44 if (!aom_read_bit(r, ACCT_STR_NAME)) {
45 return aom_read_literal(r, b, ACCT_STR_NAME) + mk;
46 }
47
48 i = i + 1;
49 mk += a;
50 }
51
52 assert(0);
53 return 0;
54 }
55
aom_read_primitive_refsubexpfin_(aom_reader * r,uint16_t n,uint16_t k,uint16_t ref ACCT_STR_PARAM)56 uint16_t aom_read_primitive_refsubexpfin_(aom_reader *r, uint16_t n, uint16_t k,
57 uint16_t ref ACCT_STR_PARAM) {
58 return inv_recenter_finite_nonneg(
59 n, ref, read_primitive_subexpfin(r, n, k, ACCT_STR_NAME));
60 }
61