The Tor Browser: media/libvpx/vp9/decoder/vp9

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /*

     2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.

     3  *

     4  *  Use of this source code is governed by a BSD-style license

     5  *  that can be found in the LICENSE file in the root of the source

     6  *  tree. An additional intellectual property rights grant can be found

     7  *  in the file PATENTS.  All contributing project authors may

     8  *  be found in the AUTHORS file in the root of the source tree.

     9  */

    11 #ifndef VP9_DECODER_VP9_DBOOLHUFF_H_

    12 #define VP9_DECODER_VP9_DBOOLHUFF_H_

    14 #include <stddef.h>

    15 #include <limits.h>

    17 #include "./vpx_config.h"

    18 #include "vpx_ports/mem.h"

    19 #include "vpx/vpx_integer.h"

    21 typedef size_t VP9_BD_VALUE;

    23 #define BD_VALUE_SIZE ((int)sizeof(VP9_BD_VALUE)*CHAR_BIT)

    25 typedef struct {

    26   const uint8_t *buffer_end;

    27   const uint8_t *buffer;

    28   VP9_BD_VALUE value;

    29   int count;

    30   unsigned int range;

    31 } vp9_reader;

    33 DECLARE_ALIGNED(16, extern const uint8_t, vp9_norm[256]);

    35 int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size);

    37 void vp9_reader_fill(vp9_reader *r);

    39 const uint8_t *vp9_reader_find_end(vp9_reader *r);

    41 static int vp9_read(vp9_reader *br, int probability) {

    42   unsigned int bit = 0;

    43   VP9_BD_VALUE value;

    44   VP9_BD_VALUE bigsplit;

    45   int count;

    46   unsigned int range;

    47   unsigned int split = ((br->range * probability) + (256 - probability)) >> 8;

    49   if (br->count < 0)

    50     vp9_reader_fill(br);

    52   value = br->value;

    53   count = br->count;

    55   bigsplit = (VP9_BD_VALUE)split << (BD_VALUE_SIZE - 8);

    57   range = split;

    59   if (value >= bigsplit) {

    60     range = br->range - split;

    61     value = value - bigsplit;

    62     bit = 1;

    63   }

    65   {

    66     register unsigned int shift = vp9_norm[range];

    67     range <<= shift;

    68     value <<= shift;

    69     count -= shift;

    70   }

    71   br->value = value;

    72   br->count = count;

    73   br->range = range;

    75   return bit;

    76 }

    78 static int vp9_read_bit(vp9_reader *r) {

    79   return vp9_read(r, 128);  // vp9_prob_half

    80 }

    82 static int vp9_read_literal(vp9_reader *br, int bits) {

    83   int z = 0, bit;

    85   for (bit = bits - 1; bit >= 0; bit--)

    86     z |= vp9_read_bit(br) << bit;

    88   return z;

    89 }

    91 int vp9_reader_has_error(vp9_reader *r);

    93 #endif  // VP9_DECODER_VP9_DBOOLHUFF_H_

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