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/*
* Copyright (c) 2017, Alliance for Open Media. All rights reserved
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*/
#include "aom_dsp/bitreader.h"
#include "av1/common/common.h"
// Inverse recenters a non-negative literal v around a reference r
static uint16_t inv_recenter_nonneg(uint16_t r, uint16_t v) {
if (v > (r << 1))
return v;
else if ((v & 1) == 0)
return (v >> 1) + r;
else
return r - ((v + 1) >> 1);
}
// Inverse recenters a non-negative literal v in [0, n-1] around a
// reference r also in [0, n-1]
static uint16_t inv_recenter_finite_nonneg(uint16_t n, uint16_t r, uint16_t v) {
if ((r << 1) <= n) {
return inv_recenter_nonneg(r, v);
} else {
return n - 1 - inv_recenter_nonneg(n - 1 - r, v);
}
}
int16_t aom_read_primitive_symmetric(aom_reader *r, unsigned int mag_bits) {
if (aom_read_bit(r, NULL)) {
int s = aom_read_bit(r, NULL);
int16_t x = aom_read_literal(r, mag_bits, NULL) + 1;
return (s > 0 ? -x : x);
} else {
return 0;
}
}
uint16_t aom_read_primitive_quniform(aom_reader *r, uint16_t n) {
if (n <= 1) return 0;
const int l = get_msb(n - 1) + 1;
const int m = (1 << l) - n;
const int v = aom_read_literal(r, l - 1, NULL);
return v < m ? v : (v << 1) - m + aom_read_bit(r, NULL);
}
uint16_t aom_read_primitive_refbilevel(aom_reader *r, uint16_t n, uint16_t p,
uint16_t ref) {
if (n <= 1) return 0;
assert(p > 0 && p <= n);
assert(ref < n);
int lolimit = ref - p / 2;
const int hilimit = lolimit + p - 1;
if (lolimit < 0) {
lolimit = 0;
} else if (hilimit >= n) {
lolimit = n - p;
}
int v;
if (aom_read_bit(r, NULL)) {
v = aom_read_primitive_quniform(r, p) + lolimit;
} else {
v = aom_read_primitive_quniform(r, n - p);
if (v >= lolimit) v += p;
}
return v;
}
// Decode finite subexponential code that for a symbol v in [0, n-1] with
// parameter k
uint16_t aom_read_primitive_subexpfin(aom_reader *r, uint16_t n, uint16_t k) {
int i = 0;
int mk = 0;
uint16_t v;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (n <= mk + 3 * a) {
v = aom_read_primitive_quniform(r, n - mk) + mk;
break;
} else {
if (aom_read_bit(r, NULL)) {
i = i + 1;
mk += a;
} else {
v = aom_read_literal(r, b, NULL) + mk;
break;
}
}
}
return v;
}
// Decode finite subexponential code that for a symbol v in [0, n-1] with
// parameter k
// based on a reference ref also in [0, n-1].
uint16_t aom_read_primitive_refsubexpfin(aom_reader *r, uint16_t n, uint16_t k,
uint16_t ref) {
return inv_recenter_finite_nonneg(n, ref,
aom_read_primitive_subexpfin(r, n, k));
}
// Decode finite subexponential code that for a symbol v in [-(n-1), n-1] with
// parameter k based on a reference ref also in [-(n-1), n-1].
int16_t aom_read_signed_primitive_refsubexpfin(aom_reader *r, uint16_t n,
uint16_t k, int16_t ref) {
ref += n - 1;
const uint16_t scaled_n = (n << 1) - 1;
return aom_read_primitive_refsubexpfin(r, scaled_n, k, ref) - n + 1;
}
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