blob: 4bed56a97942fea615e6ceb40d3188a40aa9836d [file] [log] [blame]
* Copyright (c) 2016, 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 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
#include <stddef.h>
#include <limits.h>
#include "./aom_config.h"
#include "aom_ports/mem.h"
#include "aom/aomdx.h"
#include "aom/aom_integer.h"
#include "aom_dsp/prob.h"
#ifdef __cplusplus
extern "C" {
typedef size_t BD_VALUE;
#define BD_VALUE_SIZE ((int)sizeof(BD_VALUE) * CHAR_BIT)
// This is meant to be a large, positive constant that can still be efficiently
// loaded as an immediate (on platforms like ARM, for example).
// Even relatively modest values like 100 would work fine.
#define LOTS_OF_BITS 0x40000000
struct aom_dk_reader {
// Be careful when reordering this struct, it may impact the cache negatively.
BD_VALUE value;
unsigned int range;
int count;
const uint8_t *buffer_end;
const uint8_t *buffer;
aom_decrypt_cb decrypt_cb;
void *decrypt_state;
uint8_t clear_buffer[sizeof(BD_VALUE) + 1];
int aom_dk_reader_init(struct aom_dk_reader *r, const uint8_t *buffer,
size_t size, aom_decrypt_cb decrypt_cb,
void *decrypt_state);
void aom_dk_reader_fill(struct aom_dk_reader *r);
const uint8_t *aom_dk_reader_find_end(struct aom_dk_reader *r);
static INLINE int aom_dk_reader_has_error(struct aom_dk_reader *r) {
// Check if we have reached the end of the buffer.
// Variable 'count' stores the number of bits in the 'value' buffer, minus
// 8. The top byte is part of the algorithm, and the remainder is buffered
// to be shifted into it. So if count == 8, the top 16 bits of 'value' are
// occupied, 8 for the algorithm and 8 in the buffer.
// When reading a byte from the user's buffer, count is filled with 8 and
// one byte is filled into the value buffer. When we reach the end of the
// data, count is additionally filled with LOTS_OF_BITS. So when
// count == LOTS_OF_BITS - 1, the user's data has been exhausted.
// 1 if we have tried to decode bits after the end of stream was encountered.
// 0 No error.
return r->count > BD_VALUE_SIZE && r->count < LOTS_OF_BITS;
static INLINE int aom_dk_read(struct aom_dk_reader *r, int prob) {
unsigned int bit = 0;
BD_VALUE value;
BD_VALUE bigsplit;
int count;
unsigned int range;
unsigned int split = (r->range * prob + (256 - prob)) >> CHAR_BIT;
if (r->count < 0) aom_dk_reader_fill(r);
value = r->value;
count = r->count;
bigsplit = (BD_VALUE)split << (BD_VALUE_SIZE - CHAR_BIT);
range = split;
if (value >= bigsplit) {
range = r->range - split;
value = value - bigsplit;
bit = 1;
register int shift = aom_norm[range];
range <<= shift;
value <<= shift;
count -= shift;
r->value = value;
r->count = count;
r->range = range;
return bit;
#ifdef __cplusplus
} // extern "C"