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
aom_read_primitive_quniform_(aom_reader * r,uint16_t n ACCT_STR_PARAM)15 uint16_t aom_read_primitive_quniform_(aom_reader *r,
16 uint16_t n ACCT_STR_PARAM) {
17 if (n <= 1) return 0;
18 const int l = get_msb(n) + 1;
19 const int m = (1 << l) - n;
20 const int v = aom_read_literal(r, l - 1, ACCT_STR_NAME);
21 return v < m ? v : (v << 1) - m + aom_read_bit(r, ACCT_STR_NAME);
22 }
23
24 // Decode finite subexponential code that for a symbol v in [0, n-1] with
25 // parameter k
aom_read_primitive_subexpfin_(aom_reader * r,uint16_t n,uint16_t k ACCT_STR_PARAM)26 uint16_t aom_read_primitive_subexpfin_(aom_reader *r, uint16_t n,
27 uint16_t k ACCT_STR_PARAM) {
28 int i = 0;
29 int mk = 0;
30
31 while (1) {
32 int b = (i ? k + i - 1 : k);
33 int a = (1 << b);
34
35 if (n <= mk + 3 * a) {
36 return aom_read_primitive_quniform(r, n - mk, ACCT_STR_NAME) + mk;
37 }
38
39 if (!aom_read_bit(r, ACCT_STR_NAME)) {
40 return aom_read_literal(r, b, ACCT_STR_NAME) + mk;
41 }
42
43 i = i + 1;
44 mk += a;
45 }
46
47 assert(0);
48 return 0;
49 }
50
aom_read_primitive_refsubexpfin_(aom_reader * r,uint16_t n,uint16_t k,uint16_t ref ACCT_STR_PARAM)51 uint16_t aom_read_primitive_refsubexpfin_(aom_reader *r, uint16_t n, uint16_t k,
52 uint16_t ref ACCT_STR_PARAM) {
53 return inv_recenter_finite_nonneg(
54 n, ref, aom_read_primitive_subexpfin(r, n, k, ACCT_STR_NAME));
55 }
56