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/*
* Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef tree_reader_h
#define tree_reader_h 1
#include "treecoder.h"
#include "dboolhuff.h"
typedef BOOL_DECODER vp8_reader;
#define vp8_read vp8dx_decode_bool
#define vp8_read_literal vp8_decode_value
#define vp8_read_bit( R) vp8_read( R, vp8_prob_half)
/* Intent of tree data structure is to make decoding trivial. */
static int vp8_treed_read(
vp8_reader *const r, /* !!! must return a 0 or 1 !!! */
vp8_tree t,
const vp8_prob *const p
)
{
register vp8_tree_index i = 0;
while ((i = t[ i + vp8_read(r, p[i>>1])]) > 0) ;
return -i;
}
/* Variant reads a binary number given distributions on each bit.
Note that tree is arbitrary; probability of decoding a zero
may or may not depend on previously decoded bits. */
static int vp8_treed_read_num(
vp8_reader *const r, /* !!! must return a 0 or 1 !!! */
vp8_tree t,
const vp8_prob *const p
)
{
vp8_tree_index i = 0;
int v = 0, b;
do
{
b = vp8_read(r, p[i>>1]);
v = (v << 1) + b;
}
while ((i = t[i+b]) > 0);
return v;
}
#endif /* tree_reader_h */
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