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/*
* 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 <assert.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)
{
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 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_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 ? ((1 << 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);
}
const uint8_t *dav1d_flush_get_bits(GetBits *c) {
c->bits_left = 0;
c->state = 0;
return c->ptr;
}
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