1 /*****************************************************************************
2 * bits.h : Bit handling helpers
3 *****************************************************************************
4 * Copyright (C) 2003 VLC authors and VideoLAN
7 * Authors: Laurent Aimar <fenrir@via.ecp.fr>
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU Lesser General Public License as published by
11 * the Free Software Foundation; either version 2.1 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public License
20 * along with this program; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
22 *****************************************************************************/
29 * This file defines functions, structures for handling streams of bits in vlc
38 ssize_t i_left
; /* i_count number of available bits */
41 static inline void bs_init( bs_t
*s
, const void *p_data
, size_t i_data
)
43 s
->p_start
= (void *)p_data
;
45 s
->p_end
= s
->p_start
+ i_data
;
49 static inline int bs_pos( const bs_t
*s
)
51 return( 8 * ( s
->p
- s
->p_start
) + 8 - s
->i_left
);
54 static inline int bs_eof( const bs_t
*s
)
56 return( s
->p
>= s
->p_end
? 1: 0 );
59 static inline uint32_t bs_read( bs_t
*s
, int i_count
)
61 static const uint32_t i_mask
[33] =
63 0x01, 0x03, 0x07, 0x0f,
64 0x1f, 0x3f, 0x7f, 0xff,
65 0x1ff, 0x3ff, 0x7ff, 0xfff,
66 0x1fff, 0x3fff, 0x7fff, 0xffff,
67 0x1ffff, 0x3ffff, 0x7ffff, 0xfffff,
68 0x1fffff, 0x3fffff, 0x7fffff, 0xffffff,
69 0x1ffffff, 0x3ffffff, 0x7ffffff, 0xfffffff,
70 0x1fffffff,0x3fffffff,0x7fffffff,0xffffffff};
72 uint32_t i_result
= 0;
76 if( s
->p
>= s
->p_end
)
81 if( ( i_shr
= s
->i_left
- i_count
) >= 0 )
83 /* more in the buffer than requested */
84 i_result
|= ( *s
->p
>> i_shr
)&i_mask
[i_count
];
95 /* less in the buffer than requested */
96 i_result
|= (*s
->p
&i_mask
[s
->i_left
]) << -i_shr
;
106 static inline uint32_t bs_read1( bs_t
*s
)
108 if( s
->p
< s
->p_end
)
110 unsigned int i_result
;
113 i_result
= ( *s
->p
>> s
->i_left
)&0x01;
125 static inline uint32_t bs_show( bs_t
*s
, int i_count
)
128 return bs_read( &s_tmp
, i_count
);
131 static inline void bs_skip( bs_t
*s
, ssize_t i_count
)
133 s
->i_left
-= i_count
;
137 const int i_bytes
= ( -s
->i_left
+ 8 ) / 8;
140 s
->i_left
+= 8 * i_bytes
;
144 static inline void bs_write( bs_t
*s
, int i_count
, uint32_t i_bits
)
148 if( s
->p
>= s
->p_end
)
155 if( ( i_bits
>> i_count
)&0x01 )
157 *s
->p
|= 1 << ( s
->i_left
- 1 );
161 *s
->p
&= ~( 1 << ( s
->i_left
- 1 ) );
172 static inline void bs_align( bs_t
*s
)
181 static inline void bs_align_0( bs_t
*s
)
185 bs_write( s
, s
->i_left
, 0 );
189 static inline void bs_align_1( bs_t
*s
)
191 while( s
->i_left
!= 8 )