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 */
10
11
12 #include "dboolhuff.h"
13 #include "vp8/common/common.h"
14 #include "vpx_dsp/vpx_dsp_common.h"
15
vp8dx_start_decode(BOOL_DECODER * br,const unsigned char * source,unsigned int source_sz,vpx_decrypt_cb decrypt_cb,void * decrypt_state)16 int vp8dx_start_decode(BOOL_DECODER *br,
17 const unsigned char *source,
18 unsigned int source_sz,
19 vpx_decrypt_cb decrypt_cb,
20 void *decrypt_state)
21 {
22 br->user_buffer_end = source+source_sz;
23 br->user_buffer = source;
24 br->value = 0;
25 br->count = -8;
26 br->range = 255;
27 br->decrypt_cb = decrypt_cb;
28 br->decrypt_state = decrypt_state;
29
30 if (source_sz && !source)
31 return 1;
32
33 /* Populate the buffer */
34 vp8dx_bool_decoder_fill(br);
35
36 return 0;
37 }
38
vp8dx_bool_decoder_fill(BOOL_DECODER * br)39 void vp8dx_bool_decoder_fill(BOOL_DECODER *br)
40 {
41 const unsigned char *bufptr = br->user_buffer;
42 VP8_BD_VALUE value = br->value;
43 int count = br->count;
44 int shift = VP8_BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
45 size_t bytes_left = br->user_buffer_end - bufptr;
46 size_t bits_left = bytes_left * CHAR_BIT;
47 int x = (int)(shift + CHAR_BIT - bits_left);
48 int loop_end = 0;
49 unsigned char decrypted[sizeof(VP8_BD_VALUE) + 1];
50
51 if (br->decrypt_cb) {
52 size_t n = VPXMIN(sizeof(decrypted), bytes_left);
53 br->decrypt_cb(br->decrypt_state, bufptr, decrypted, (int)n);
54 bufptr = decrypted;
55 }
56
57 if(x >= 0)
58 {
59 count += VP8_LOTS_OF_BITS;
60 loop_end = x;
61 }
62
63 if (x < 0 || bits_left)
64 {
65 while(shift >= loop_end)
66 {
67 count += CHAR_BIT;
68 value |= (VP8_BD_VALUE)*bufptr << shift;
69 ++bufptr;
70 ++br->user_buffer;
71 shift -= CHAR_BIT;
72 }
73 }
74
75 br->value = value;
76 br->count = count;
77 }
78