2 * Extracted 2009 from mplayer 2009-02-10 libavcodec/bitstream.h.
4 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
6 * Licensed under the GNU Lesser General Public License.
7 * For licencing details see COPYING.LIB.
10 /** \file bitstream.h Bitstream structures and inline functions. */
12 /** Structure for bistream I/O. */
13 struct getbit_context
{
14 /* Start of the internal buffer. */
15 const uint8_t *buffer
;
16 /* End of the internal buffer. */
17 const uint8_t *buffer_end
;
22 #define VLC_TYPE int16_t
24 /** A variable length code table. */
26 /** Number of bits of the table. */
28 /** The code and the bits table. */
30 /** The size of the table. */
32 /** Amount of memory allocated so far. */
36 static inline uint32_t show_bits(struct getbit_context
*gbc
, int num
)
39 const uint8_t *p
= gbc
->buffer
+ (idx
>> 3);
40 uint32_t x
= ((p
[0] << 24) | (p
[1] << 16) | (p
[2] << 8) | p
[3]);
41 return (x
<< (idx
& 7)) >> (32 - num
);
44 static inline int get_bits_count(struct getbit_context
*gbc
)
49 static inline void skip_bits(struct getbit_context
*gbc
, int n
)
54 static inline unsigned int get_bits(struct getbit_context
*gbc
, int n
)
56 unsigned int ret
= show_bits(gbc
, n
);
61 /* This is rather hot, we can do better than get_bits(gbc, 1). */
62 static inline unsigned int get_bit(struct getbit_context
*gbc
)
64 int idx
= gbc
->index
++;
65 uint8_t tmp
= gbc
->buffer
[idx
>> 3], mask
= (1 << (7 - (idx
& 7)));
66 return !!(tmp
& mask
);
70 * Initialize a getbit_context structure.
72 * \param buffer The bitstream buffer. It must be 4 bytes larger then the
73 * actual read bits because the bitstream reader might read 32 bits at once and
74 * could read over the end.
76 * \param bit_size The size of the buffer in bytes.
78 static inline void init_get_bits(struct getbit_context
*gbc
,
79 const uint8_t *buffer
, int size
)
82 gbc
->buffer_end
= buffer
+ size
;
86 void init_vlc(struct vlc
*vlc
, int nb_bits
, int nb_codes
, const void *bits
,
87 const void *codes
, int codes_size
);
88 void free_vlc(struct vlc
*vlc
);
89 int get_vlc(struct getbit_context
*gbc
, VLC_TYPE(*table
)[2], int bits
,