1593b99ee5bda9fe6f7e47b6ab63c445a10ad529
[paraslash.git] / bitstream.c
1 /*
2 * Common bit I/O utils.
3 *
4 * Extracted 2009 from mplayer 2009-02-10 libavcodec/bitstream.c.
5 *
6 * Copyright (c) 2000, 2001 Fabrice Bellard
7 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
8 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
9 *
10 * Licensed under the GNU Lesser General Public License.
11 * For licencing details see COPYING.LIB.
12 */
13
14 /** \file bitstream.c Bitstream API for the wma decoder. */
15
16 #include <regex.h>
17
18 #include "para.h"
19 #include "error.h"
20 #include "string.h"
21 #include "wma.h"
22 #include "bitstream.h"
23
24 static inline uint32_t get_data(const void *table, int i, int size)
25 {
26 const uint8_t *ptr = (const uint8_t *)table + i * size;
27 uint32_t v;
28
29 switch (size) {
30 case 1:
31 v = *(const uint8_t *)ptr;
32 break;
33 case 2:
34 v = *(const uint16_t *)ptr;
35 break;
36 default:
37 v = *(const uint32_t *)ptr;
38 break;
39 }
40 return v;
41 }
42
43 static void alloc_table(struct vlc *vlc, int size)
44 {
45 vlc->table_size += size;
46 if (vlc->table_size > vlc->table_allocated) {
47 vlc->table_allocated += (1 << vlc->bits);
48 vlc->table = para_realloc(vlc->table,
49 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
50 }
51 }
52
53 static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
54 const void *bits, const void *codes, int codes_size,
55 uint32_t code_prefix, int n_prefix)
56 {
57 int i, j, k, n, table_size, table_index, nb, n1, idx;
58 uint32_t code;
59 VLC_TYPE(*table)[2];
60
61 table_size = 1 << table_nb_bits;
62 table_index = vlc->table_size;
63 alloc_table(vlc, table_size);
64 table = &vlc->table[table_index];
65
66 for (i = 0; i < table_size; i++) {
67 table[i][1] = 0; /* bits */
68 table[i][0] = -1; /* codes */
69 }
70
71 /* map codes and compute auxiliary table sizes */
72 for (i = 0; i < nb_codes; i++) {
73 n = get_data(bits, i, 1);
74 /* we accept tables with holes */
75 n -= n_prefix;
76 if (n <= 0)
77 continue;
78 code = get_data(codes, i, codes_size);
79 /* if code matches the prefix, it is in the table */
80 if ((code >> n) != code_prefix)
81 continue;
82 if (n <= table_nb_bits) {
83 /* no need to add another table */
84 j = (code << (table_nb_bits - n)) & (table_size - 1);
85 nb = 1 << (table_nb_bits - n);
86 for (k = 0; k < nb; k++) {
87 assert(table[j][1] == 0); /* incorrect code */
88 table[j][1] = n; /* bits */
89 table[j][0] = i;
90 j++;
91 }
92 } else {
93 n -= table_nb_bits;
94 j = (code >> n) & ((1 << table_nb_bits) - 1);
95 /* compute table size */
96 n1 = -table[j][1]; /* bits */
97 if (n > n1)
98 n1 = n;
99 table[j][1] = -n1; /* bits */
100 }
101 }
102
103 /* fill auxiliary tables recursively */
104 for (i = 0; i < table_size; i++) {
105 n = table[i][1]; /* bits */
106 if (n < 0) {
107 n = -n;
108 if (n > table_nb_bits) {
109 n = table_nb_bits;
110 table[i][1] = -n; /* bits */
111 }
112 idx = build_table(vlc, n, nb_codes, bits, codes,
113 codes_size, (code_prefix << table_nb_bits) | i,
114 n_prefix + table_nb_bits);
115 /* vlc->table might have changed */
116 table = &vlc->table[table_index];
117 table[i][0] = idx; /* code */
118 }
119 }
120 return table_index;
121 }
122
123 /**
124 * Build VLC decoding tables suitable for use with get_vlc().
125 *
126 * \param vlc The structure to be initialized.
127 * \param nb_bits Set the decoding table size (2^nb_bits) entries.
128 * \param nb_codes Number of vlc codes.
129 * \param bits Table which gives the size (in bits) of each vlc code.
130 * \param codes Table which gives the bit pattern of of each vlc code.
131 * \param codes_size The number of bytes of each entry of the \a codes tables.
132 *
133 * The bigger \a nb_bits is, the faster is the decoding. But it should not be
134 * too big to save memory and L1 cache. '9' is a good compromise.
135 *
136 * The wrap and size parameters allow to use any memory configuration and
137 * types (byte/word/long) to store the bits and codes tables.
138 */
139 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
140 const void *codes, int codes_size)
141 {
142 PARA_INFO_LOG("nb_codes: %d\n", nb_codes);
143 vlc->bits = nb_bits;
144 vlc->table = NULL;
145 vlc->table_allocated = 0;
146 vlc->table_size = 0;
147 build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
148 }
149
150 /**
151 * Deallocate all resources of a VLC table.
152 *
153 * \param vlc Pointer to an initialized vlc structure.
154 *
155 * The table given by \a vlc must have been initialized earlier via \ref
156 * init_vlc().
157 */
158 void free_vlc(struct vlc *vlc)
159 {
160 freep(&vlc->table);
161 }
162
163 /**
164 * Parse a vlc code.
165 *
166 * \param gbc The getbit context structure.
167 * \param table The vlc tables to use.
168 * \param bits The number of bits which will be read at once.
169 * \param max_depth The number of times \a bits bits must be read to completely
170 * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
171 *
172 * The \a bits parameter must be identical to the \a nb_bits value supplied to
173 * \ref init_vlc().
174 *
175 * \return The vlc code.
176 */
177 int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
178 int max_depth)
179 {
180 int n, idx, nb_bits, code;
181
182 idx = show_bits(gbc, bits);
183 code = table[idx][0];
184 n = table[idx][1];
185 if (max_depth > 1 && n < 0) {
186 skip_bits(gbc, bits);
187 nb_bits = -n;
188 idx = show_bits(gbc, nb_bits) + code;
189 code = table[idx][0];
190 n = table[idx][1];
191 if (max_depth > 2 && n < 0) {
192 skip_bits(gbc, nb_bits);
193 nb_bits = -n;
194 idx = show_bits(gbc, nb_bits) + code;
195 code = table[idx][0];
196 n = table[idx][1];
197 }
198 }
199 skip_bits(gbc, n);
200 return code >= 0? code : -E_VLC;
201 }