Replace GET_VLC by an inline funcion and kill get_vlc2().
[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 #define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
18
19 /** Structure for bistream I/O. */
20 struct getbit_context {
21 /* Start of the internal buffer. */
22 const uint8_t *buffer;
23 /* End of the internal buffer. */
24 const uint8_t *buffer_end;
25 /** Bit counter. */
26 int index;
27 };
28
29 #define VLC_TYPE int16_t
30
31 struct vlc {
32 int bits;
33 VLC_TYPE(*table)[2]; ///< code, bits
34 int table_size, table_allocated;
35 };
36
37 /** Load \a gb into local variables. */
38 #define OPEN_READER(name, gb)\
39 int name##_index= (gb)->index;\
40 int name##_cache= 0;\
41
42 /** Store local vars in gb. */
43 #define CLOSE_READER(name, gb)\
44 (gb)->index= name##_index;\
45
46 /**
47 * Refill the internal cache from the bitstream.
48 */
49 #define UPDATE_CACHE(name, gb)\
50 name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer) \
51 + (name##_index >> 3) ) << (name##_index & 0x07);\
52
53 /**
54 * Remove the next num bits from the cache.
55 *
56 * SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER).
57 */
58 #define SKIP_CACHE(name, gb, num)\
59 name##_cache <<= (num);
60
61 /**
62 * Increment the internal bit counter.
63 *
64 * \sa SKIP_CACHE, SKIP_BITS.
65 */
66 #define SKIP_COUNTER(name, gb, num)\
67 name##_index += (num);\
68
69 /**
70 * Skip over the next num bits.
71 *
72 * This is equivalent to SKIP_CACHE; SKIP_COUNTER.
73 */
74 #define SKIP_BITS(name, gb, num)\
75 {\
76 SKIP_CACHE(name, gb, num)\
77 SKIP_COUNTER(name, gb, num)\
78 }\
79
80 /** This is equivalent to SKIP_LAST_CACHE; SKIP_COUNTER. */
81 #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
82
83 /** Return the next num bits. */
84 #define SHOW_UBITS(name, gb, num)\
85 NEG_USR32(name##_cache, num)
86
87 static inline int get_bits_count(struct getbit_context *s)
88 {
89 return s->index;
90 }
91
92 /**
93 * Read 1-17 bits.
94 */
95 static inline unsigned int get_bits(struct getbit_context *s, int n)
96 {
97 register int tmp;
98 OPEN_READER(re, s)
99 UPDATE_CACHE(re, s)
100 tmp = SHOW_UBITS(re, s, n);
101 LAST_SKIP_BITS(re, s, n)
102 CLOSE_READER(re, s)
103 return tmp;
104 }
105
106 static inline void skip_bits(struct getbit_context *s, int n)
107 {
108 /* gcc seems to optimize this to s->index+=n for the ALT_READER :)) */
109 OPEN_READER(re, s)
110 UPDATE_CACHE(re, s)
111 LAST_SKIP_BITS(re, s, n)
112 CLOSE_READER(re, s)
113 }
114
115 static inline unsigned int get_bits1(struct getbit_context *s)
116 {
117 int idx = s->index;
118 uint8_t result = s->buffer[idx >> 3];
119
120 result <<= (idx & 0x07);
121 result >>= 8 - 1;
122 idx++;
123 s->index = idx;
124 return result;
125 }
126
127 /**
128 * Initialize a getbit_context structure.
129 *
130 * \param buffer The bitstream buffer. It must be FF_INPUT_BUFFER_PADDING_SIZE
131 * bytes larger then the actual read bits * because some optimized bitstream
132 * readers read 32 or 64 bit at once and could read over the end.
133 *
134 * \param bit_size The size of the buffer in bits.
135 */
136 static inline void init_get_bits(struct getbit_context *s,
137 const uint8_t *buffer, int bit_size)
138 {
139 int buffer_size = (bit_size + 7) >> 3;
140 if (buffer_size < 0 || bit_size < 0) {
141 buffer_size = bit_size = 0;
142 buffer = NULL;
143 }
144 s->buffer = buffer;
145 s->buffer_end = buffer + buffer_size;
146 s->index = 0;
147 }
148
149 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
150 const void *codes, int codes_size);
151
152 void free_vlc(struct vlc *vlc);
153
154 /**
155 * Parse a vlc code.
156 *
157 * \param bits The number of bits which will be read at once, must be
158 * identical to nb_bits in init_vlc()
159 *
160 * \param max_depth The number of times bits bits must be read to completely
161 * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
162 */
163 static inline int get_vlc(struct getbit_context *gb, VLC_TYPE(*table)[2],
164 int bits, int max_depth)
165 {
166 int n, idx, nb_bits, code;
167
168 OPEN_READER(re, gb)
169 UPDATE_CACHE(re, gb)
170 idx = SHOW_UBITS(re, gb, bits);
171 code = table[idx][0];
172 n = table[idx][1];
173 if (max_depth > 1 && n < 0) {
174 LAST_SKIP_BITS(re, gb, bits)
175 UPDATE_CACHE(re, gb)
176 nb_bits = -n;
177 idx = SHOW_UBITS(re, gb, nb_bits) + code;
178 code = table[idx][0];
179 n = table[idx][1];
180 if (max_depth > 2 && n < 0) {
181 LAST_SKIP_BITS(re, gb, nb_bits)
182 UPDATE_CACHE(re, gb)
183 nb_bits = -n;
184 idx = SHOW_UBITS(re, gb, nb_bits) + code;
185 code = table[idx][0];
186 n = table[idx][1];
187 }
188 }
189 SKIP_BITS(re, gb, n)
190 CLOSE_READER(re, gb)
191 return code;
192 }