blob: aa7a56a021b13a538fb924f90e15e0e8ccb233e1 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
/*
* Copyright (c) 2010 The WebM 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.
*/
#include "dboolhuff.h"
int vp8dx_start_decode(BOOL_DECODER *br,
const unsigned char *source,
unsigned int source_sz,
const unsigned char *origin,
const unsigned char *key)
{
br->user_buffer_end = source+source_sz;
br->user_buffer = source;
br->value = 0;
br->count = -8;
br->range = 255;
br->origin = origin;
br->key = key;
if (source_sz && !source)
return 1;
/* Populate the buffer */
vp8dx_bool_decoder_fill(br);
return 0;
}
void vp8dx_bool_decoder_fill(BOOL_DECODER *br)
{
const unsigned char *bufptr = br->user_buffer;
const unsigned char *bufend = br->user_buffer_end;
VP8_BD_VALUE value = br->value;
int count = br->count;
int shift = VP8_BD_VALUE_SIZE - 8 - (count + 8);
size_t bits_left = (bufend - bufptr)*CHAR_BIT;
int x = (int)(shift + CHAR_BIT - bits_left);
int loop_end = 0;
if(x >= 0)
{
count += VP8_LOTS_OF_BITS;
loop_end = x;
}
if (x < 0 || bits_left)
{
while(shift >= loop_end)
{
count += CHAR_BIT;
value |= ((VP8_BD_VALUE)decrypt_byte(bufptr, br->origin,
br->key)) << shift;
++bufptr;
shift -= CHAR_BIT;
}
}
br->user_buffer = bufptr;
br->value = value;
br->count = count;
}
|
