7f99c3c59a
Removing redundant 'extern' keywords, fixing formatting and #include order, code simplification. Change-Id: I0e5fdc8009010f3f885f13b5d76859b9da511758
124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/*
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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 VP9_BD_VALUE_SIZE ((int)sizeof(VP9_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 VP9_LOTS_OF_BITS (0x40000000)
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typedef struct {
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const unsigned char *user_buffer_end;
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const unsigned char *user_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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} BOOL_DECODER;
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DECLARE_ALIGNED(16, extern const uint8_t, vp9_norm[256]);
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int vp9_start_decode(BOOL_DECODER *br,
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const unsigned char *source,
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unsigned int source_sz);
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void vp9_bool_decoder_fill(BOOL_DECODER *br);
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int vp9_decode_uniform(BOOL_DECODER *br, int n);
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int vp9_decode_term_subexp(BOOL_DECODER *br, int k, int num_syms);
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int vp9_inv_recenter_nonneg(int v, int m);
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static int decode_bool(BOOL_DECODER *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 = 1 + (((br->range - 1) * probability) >> 8);
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if (br->count < 0)
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vp9_bool_decoder_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 << (VP9_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 decode_value(BOOL_DECODER *br, int bits) {
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int z = 0;
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int bit;
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for (bit = bits - 1; bit >= 0; bit--) {
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z |= (decode_bool(br, 0x80) << bit);
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}
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return z;
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}
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static int bool_error(BOOL_DECODER *br) {
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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 VP9_LOTS_OF_BITS. So when
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* count == VP9_LOTS_OF_BITS - 1, the user's data has been exhausted.
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*/
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if ((br->count > VP9_BD_VALUE_SIZE) && (br->count < VP9_LOTS_OF_BITS)) {
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/* We have tried to decode bits after the end of
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* stream was encountered.
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*/
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return 1;
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}
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/* No error. */
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return 0;
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}
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int vp9_decode_unsigned_max(BOOL_DECODER *br, int max);
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#endif // VP9_DECODER_VP9_DBOOLHUFF_H_
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