143 строки
4.1 KiB
C
143 строки
4.1 KiB
C
/*
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* Copyright (c) 2016, Alliance for Open Media. All rights reserved
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*
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* This source code is subject to the terms of the BSD 2 Clause License and
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* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
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* was not distributed with this source code in the LICENSE file, you can
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* obtain it at www.aomedia.org/license/software. If the Alliance for Open
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* Media Patent License 1.0 was not distributed with this source code in the
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* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
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*/
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#ifndef AOM_DSP_DKBOOLREADER_H_
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#define AOM_DSP_DKBOOLREADER_H_
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#include <stddef.h>
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#include <limits.h>
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#include "./aom_config.h"
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#if CONFIG_BITSTREAM_DEBUG
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#include <assert.h>
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#include <stdio.h>
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#include "aom_util/debug_util.h"
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#endif // CONFIG_BITSTREAM_DEBUG
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#include "aom_ports/mem.h"
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#include "aom/aomdx.h"
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#include "aom/aom_integer.h"
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#include "aom_dsp/prob.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef size_t BD_VALUE;
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#define BD_VALUE_SIZE ((int)sizeof(BD_VALUE) * CHAR_BIT)
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// This is meant to be a large, positive constant that can still be efficiently
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// loaded as an immediate (on platforms like ARM, for example).
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// Even relatively modest values like 100 would work fine.
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#define LOTS_OF_BITS 0x40000000
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struct aom_dk_reader {
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// Be careful when reordering this struct, it may impact the cache negatively.
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BD_VALUE value;
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unsigned int range;
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int count;
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const uint8_t *buffer_end;
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const uint8_t *buffer;
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aom_decrypt_cb decrypt_cb;
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void *decrypt_state;
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uint8_t clear_buffer[sizeof(BD_VALUE) + 1];
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};
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int aom_dk_reader_init(struct aom_dk_reader *r, const uint8_t *buffer,
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size_t size, aom_decrypt_cb decrypt_cb,
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void *decrypt_state);
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void aom_dk_reader_fill(struct aom_dk_reader *r);
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const uint8_t *aom_dk_reader_find_end(struct aom_dk_reader *r);
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static INLINE int aom_dk_reader_has_error(struct aom_dk_reader *r) {
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// Check if we have reached the end of the buffer.
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//
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// Variable 'count' stores the number of bits in the 'value' buffer, minus
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// 8. The top byte is part of the algorithm, and the remainder is buffered
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// to be shifted into it. So if count == 8, the top 16 bits of 'value' are
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// occupied, 8 for the algorithm and 8 in the buffer.
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//
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// When reading a byte from the user's buffer, count is filled with 8 and
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// one byte is filled into the value buffer. When we reach the end of the
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// data, count is additionally filled with LOTS_OF_BITS. So when
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// count == LOTS_OF_BITS - 1, the user's data has been exhausted.
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//
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// 1 if we have tried to decode bits after the end of stream was encountered.
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// 0 No error.
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return r->count > BD_VALUE_SIZE && r->count < LOTS_OF_BITS;
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}
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static INLINE int aom_dk_read(struct aom_dk_reader *r, int prob) {
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unsigned int bit = 0;
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BD_VALUE value;
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BD_VALUE bigsplit;
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int count;
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unsigned int range;
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unsigned int split = (r->range * prob + (256 - prob)) >> CHAR_BIT;
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if (r->count < 0) aom_dk_reader_fill(r);
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value = r->value;
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count = r->count;
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bigsplit = (BD_VALUE)split << (BD_VALUE_SIZE - CHAR_BIT);
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range = split;
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if (value >= bigsplit) {
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range = r->range - split;
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value = value - bigsplit;
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bit = 1;
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}
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{
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register int shift = aom_norm[range];
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range <<= shift;
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value <<= shift;
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count -= shift;
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}
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r->value = value;
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r->count = count;
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r->range = range;
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#if CONFIG_BITSTREAM_DEBUG
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{
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int ref_bit, ref_prob;
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const int queue_r = bitstream_queue_get_read();
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const int frame_idx = bitstream_queue_get_frame_read();
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bitstream_queue_pop(&ref_bit, &ref_prob);
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if (prob != ref_prob) {
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fprintf(
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stderr,
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"\n *** prob error, frame_idx_r %d prob %d ref_prob %d queue_r %d\n",
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frame_idx, prob, ref_prob, queue_r);
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assert(0);
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}
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if ((int)bit != ref_bit) {
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fprintf(stderr, "\n *** bit error, frame_idx_r %d bit %d ref_bit %d\n",
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frame_idx, bit, ref_bit);
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assert(0);
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}
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}
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#endif // CONFIG_BITSTREAM_DEBUG
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return bit;
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}
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif // AOM_DSP_DKBOOLREADER_H_
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