1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/libvpx/vp8/decoder/dboolhuff.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,138 @@
1.4 +/*
1.5 + * Copyright (c) 2010 The WebM project authors. All Rights Reserved.
1.6 + *
1.7 + * Use of this source code is governed by a BSD-style license
1.8 + * that can be found in the LICENSE file in the root of the source
1.9 + * tree. An additional intellectual property rights grant can be found
1.10 + * in the file PATENTS. All contributing project authors may
1.11 + * be found in the AUTHORS file in the root of the source tree.
1.12 + */
1.13 +
1.14 +
1.15 +#ifndef DBOOLHUFF_H_
1.16 +#define DBOOLHUFF_H_
1.17 +
1.18 +#include <stddef.h>
1.19 +#include <limits.h>
1.20 +
1.21 +#include "vpx_config.h"
1.22 +#include "vpx_ports/mem.h"
1.23 +#include "vpx/vpx_integer.h"
1.24 +
1.25 +typedef size_t VP8_BD_VALUE;
1.26 +
1.27 +#define VP8_BD_VALUE_SIZE ((int)sizeof(VP8_BD_VALUE)*CHAR_BIT)
1.28 +
1.29 +/*This is meant to be a large, positive constant that can still be efficiently
1.30 + loaded as an immediate (on platforms like ARM, for example).
1.31 + Even relatively modest values like 100 would work fine.*/
1.32 +#define VP8_LOTS_OF_BITS (0x40000000)
1.33 +
1.34 +/*Decrypt n bytes of data from input -> output, using the decrypt_state
1.35 + passed in VP8D_SET_DECRYPTOR.
1.36 +*/
1.37 +typedef void (vp8_decrypt_cb)(void *decrypt_state, const unsigned char *input,
1.38 + unsigned char *output, int count);
1.39 +
1.40 +typedef struct
1.41 +{
1.42 + const unsigned char *user_buffer_end;
1.43 + const unsigned char *user_buffer;
1.44 + VP8_BD_VALUE value;
1.45 + int count;
1.46 + unsigned int range;
1.47 + vp8_decrypt_cb *decrypt_cb;
1.48 + void *decrypt_state;
1.49 +} BOOL_DECODER;
1.50 +
1.51 +DECLARE_ALIGNED(16, extern const unsigned char, vp8_norm[256]);
1.52 +
1.53 +int vp8dx_start_decode(BOOL_DECODER *br,
1.54 + const unsigned char *source,
1.55 + unsigned int source_sz,
1.56 + vp8_decrypt_cb *decrypt_cb,
1.57 + void *decrypt_state);
1.58 +
1.59 +void vp8dx_bool_decoder_fill(BOOL_DECODER *br);
1.60 +
1.61 +
1.62 +static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
1.63 + unsigned int bit = 0;
1.64 + VP8_BD_VALUE value;
1.65 + unsigned int split;
1.66 + VP8_BD_VALUE bigsplit;
1.67 + int count;
1.68 + unsigned int range;
1.69 +
1.70 + split = 1 + (((br->range - 1) * probability) >> 8);
1.71 +
1.72 + if(br->count < 0)
1.73 + vp8dx_bool_decoder_fill(br);
1.74 +
1.75 + value = br->value;
1.76 + count = br->count;
1.77 +
1.78 + bigsplit = (VP8_BD_VALUE)split << (VP8_BD_VALUE_SIZE - 8);
1.79 +
1.80 + range = split;
1.81 +
1.82 + if (value >= bigsplit)
1.83 + {
1.84 + range = br->range - split;
1.85 + value = value - bigsplit;
1.86 + bit = 1;
1.87 + }
1.88 +
1.89 + {
1.90 + register unsigned int shift = vp8_norm[range];
1.91 + range <<= shift;
1.92 + value <<= shift;
1.93 + count -= shift;
1.94 + }
1.95 + br->value = value;
1.96 + br->count = count;
1.97 + br->range = range;
1.98 +
1.99 + return bit;
1.100 +}
1.101 +
1.102 +static int vp8_decode_value(BOOL_DECODER *br, int bits)
1.103 +{
1.104 + int z = 0;
1.105 + int bit;
1.106 +
1.107 + for (bit = bits - 1; bit >= 0; bit--)
1.108 + {
1.109 + z |= (vp8dx_decode_bool(br, 0x80) << bit);
1.110 + }
1.111 +
1.112 + return z;
1.113 +}
1.114 +
1.115 +static int vp8dx_bool_error(BOOL_DECODER *br)
1.116 +{
1.117 + /* Check if we have reached the end of the buffer.
1.118 + *
1.119 + * Variable 'count' stores the number of bits in the 'value' buffer, minus
1.120 + * 8. The top byte is part of the algorithm, and the remainder is buffered
1.121 + * to be shifted into it. So if count == 8, the top 16 bits of 'value' are
1.122 + * occupied, 8 for the algorithm and 8 in the buffer.
1.123 + *
1.124 + * When reading a byte from the user's buffer, count is filled with 8 and
1.125 + * one byte is filled into the value buffer. When we reach the end of the
1.126 + * data, count is additionally filled with VP8_LOTS_OF_BITS. So when
1.127 + * count == VP8_LOTS_OF_BITS - 1, the user's data has been exhausted.
1.128 + */
1.129 + if ((br->count > VP8_BD_VALUE_SIZE) && (br->count < VP8_LOTS_OF_BITS))
1.130 + {
1.131 + /* We have tried to decode bits after the end of
1.132 + * stream was encountered.
1.133 + */
1.134 + return 1;
1.135 + }
1.136 +
1.137 + /* No error. */
1.138 + return 0;
1.139 +}
1.140 +
1.141 +#endif // DBOOLHUFF_H_
