зеркало из https://github.com/mozilla/gecko-dev.git
94 строки
2.1 KiB
C
94 строки
2.1 KiB
C
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/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef VP9_DECODER_VP9_DBOOLHUFF_H_
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#define VP9_DECODER_VP9_DBOOLHUFF_H_
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#include <stddef.h>
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#include <limits.h>
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#include "./vpx_config.h"
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#include "vpx_ports/mem.h"
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#include "vpx/vpx_integer.h"
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typedef size_t VP9_BD_VALUE;
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#define BD_VALUE_SIZE ((int)sizeof(VP9_BD_VALUE)*CHAR_BIT)
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typedef struct {
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const uint8_t *buffer_end;
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const uint8_t *buffer;
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VP9_BD_VALUE value;
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int count;
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unsigned int range;
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} vp9_reader;
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DECLARE_ALIGNED(16, extern const uint8_t, vp9_norm[256]);
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int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size);
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void vp9_reader_fill(vp9_reader *r);
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const uint8_t *vp9_reader_find_end(vp9_reader *r);
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static int vp9_read(vp9_reader *br, int probability) {
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unsigned int bit = 0;
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VP9_BD_VALUE value;
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VP9_BD_VALUE bigsplit;
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int count;
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unsigned int range;
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unsigned int split = ((br->range * probability) + (256 - probability)) >> 8;
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if (br->count < 0)
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vp9_reader_fill(br);
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value = br->value;
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count = br->count;
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bigsplit = (VP9_BD_VALUE)split << (BD_VALUE_SIZE - 8);
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range = split;
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if (value >= bigsplit) {
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range = br->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 unsigned int shift = vp9_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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br->value = value;
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br->count = count;
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br->range = range;
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return bit;
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}
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static int vp9_read_bit(vp9_reader *r) {
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return vp9_read(r, 128); // vp9_prob_half
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}
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static int vp9_read_literal(vp9_reader *br, int bits) {
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int z = 0, bit;
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for (bit = bits - 1; bit >= 0; bit--)
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z |= vp9_read_bit(br) << bit;
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return z;
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}
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int vp9_reader_has_error(vp9_reader *r);
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#endif // VP9_DECODER_VP9_DBOOLHUFF_H_
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