open code NEG_USR32
[paraslash.git] / bitstream.h
1 /*
2 * Extracted 2009 from mplayer 2009-02-10 libavcodec/bitstream.h.
3 *
4 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
5 *
6 * Licensed under the GNU Lesser General Public License.
7 * For licencing details see COPYING.LIB.
8 */
9
10 /** \file bitstream.h Bitstream structures and inline functions. */
11
12 #define AV_RB32(x) ((((const uint8_t*)(x))[0] << 24) | \
13 (((const uint8_t*)(x))[1] << 16) | \
14 (((const uint8_t*)(x))[2] << 8) | \
15 ((const uint8_t*)(x))[3])
16
17 /** Structure for bistream I/O. */
18 struct getbit_context {
19 /* Start of the internal buffer. */
20 const uint8_t *buffer;
21 /* End of the internal buffer. */
22 const uint8_t *buffer_end;
23 /** Bit counter. */
24 int index;
25 };
26
27 #define VLC_TYPE int16_t
28
29 struct vlc {
30 int bits;
31 VLC_TYPE(*table)[2]; ///< code, bits
32 int table_size, table_allocated;
33 };
34
35 /** Load \a gb into local variables. */
36 #define OPEN_READER(name, gb)\
37 int name##_index= (gb)->index;\
38 int name##_cache= 0;\
39
40 /** Store local vars in gb. */
41 #define CLOSE_READER(name, gb)\
42 (gb)->index= name##_index;\
43
44 /**
45 * Refill the internal cache from the bitstream.
46 */
47 #define UPDATE_CACHE(name, gb)\
48 name##_cache= AV_RB32( ((gb)->buffer) \
49 + (name##_index >> 3) ) << (name##_index & 0x07);\
50
51 /**
52 * Remove the next num bits from the cache.
53 *
54 * SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER).
55 */
56 #define SKIP_CACHE(name, gb, num)\
57 name##_cache <<= (num);
58
59 /**
60 * Increment the internal bit counter.
61 *
62 * \sa SKIP_CACHE.
63 */
64 #define SKIP_COUNTER(name, gb, num)\
65 name##_index += (num);\
66
67 /** Return the next num bits. */
68 #define SHOW_UBITS(name, gb, num) \
69 (((uint32_t)(name##_cache)) >> (32 - (num)))
70
71 static inline int get_bits_count(struct getbit_context *s)
72 {
73 return s->index;
74 }
75
76 /**
77 * Read 1-17 bits.
78 */
79 static inline unsigned int get_bits(struct getbit_context *s, int n)
80 {
81 register int tmp;
82 OPEN_READER(re, s)
83 UPDATE_CACHE(re, s)
84 tmp = SHOW_UBITS(re, s, n);
85 SKIP_COUNTER(re, s, n)
86 CLOSE_READER(re, s)
87 return tmp;
88 }
89
90 static inline void skip_bits(struct getbit_context *s, int n)
91 {
92 s->index += n;
93 }
94
95 static inline unsigned int get_bits1(struct getbit_context *s)
96 {
97 int idx = s->index;
98 uint8_t result = s->buffer[idx >> 3];
99
100 result <<= (idx & 0x07);
101 result >>= 8 - 1;
102 idx++;
103 s->index = idx;
104 return result;
105 }
106
107 /**
108 * Initialize a getbit_context structure.
109 *
110 * \param buffer The bitstream buffer. It must be FF_INPUT_BUFFER_PADDING_SIZE
111 * bytes larger then the actual read bits * because some optimized bitstream
112 * readers read 32 or 64 bit at once and could read over the end.
113 *
114 * \param bit_size The size of the buffer in bytes.
115 */
116 static inline void init_get_bits(struct getbit_context *s,
117 const uint8_t *buffer, int size)
118 {
119 s->buffer = buffer;
120 s->buffer_end = buffer + size;
121 s->index = 0;
122 }
123
124 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
125 const void *codes, int codes_size);
126
127 void free_vlc(struct vlc *vlc);
128
129 /**
130 * Parse a vlc code.
131 *
132 * \param bits The number of bits which will be read at once, must be
133 * identical to nb_bits in init_vlc()
134 *
135 * \param max_depth The number of times bits bits must be read to completely
136 * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
137 */
138 static inline int get_vlc(struct getbit_context *gb, VLC_TYPE(*table)[2],
139 int bits, int max_depth)
140 {
141 int n, idx, nb_bits, code;
142
143 OPEN_READER(re, gb)
144 UPDATE_CACHE(re, gb)
145 idx = SHOW_UBITS(re, gb, bits);
146 code = table[idx][0];
147 n = table[idx][1];
148 if (max_depth > 1 && n < 0) {
149 SKIP_COUNTER(re, gb, bits)
150 UPDATE_CACHE(re, gb)
151 nb_bits = -n;
152 idx = SHOW_UBITS(re, gb, nb_bits) + code;
153 code = table[idx][0];
154 n = table[idx][1];
155 if (max_depth > 2 && n < 0) {
156 SKIP_COUNTER(re, gb, nb_bits)
157 UPDATE_CACHE(re, gb)
158 nb_bits = -n;
159 idx = SHOW_UBITS(re, gb, nb_bits) + code;
160 code = table[idx][0];
161 n = table[idx][1];
162 }
163 }
164 SKIP_CACHE(re, gb, n)
165 SKIP_COUNTER(re, gb, n)
166 CLOSE_READER(re, gb)
167 return code;
168 }