Merge branch 'maint'
[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 <stdlib.h>
17 #include <inttypes.h>
18 #include <stdio.h>
19 #include <string.h>
20 #include <regex.h>
21
22 #include "para.h"
23 #include "error.h"
24 #include "string.h"
25 #include "wma.h"
26 #include "bitstream.h"
27
28 /** Read an 8, 16, or 32 bit entity from a VLC table. */
29 #define GET_DATA(v, table, i, size) \
30 {\
31 const uint8_t *ptr = (const uint8_t *)table + i * size; \
32 switch (size) { \
33 case 1: \
34 v = *(const uint8_t *)ptr; \
35 break; \
36 case 2: \
37 v = *(const uint16_t *)ptr; \
38 break; \
39 default: \
40 v = *(const uint32_t *)ptr; \
41 break; \
42 } \
43 }
44
45 static void alloc_table(struct vlc *vlc, int size)
46 {
47 vlc->table_size += size;
48 if (vlc->table_size > vlc->table_allocated) {
49 vlc->table_allocated += (1 << vlc->bits);
50 vlc->table = para_realloc(vlc->table,
51 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
52 }
53 }
54
55 static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
56 const void *bits, const void *codes, int codes_size,
57 uint32_t code_prefix, int n_prefix)
58 {
59 int i, j, k, n, table_size, table_index, nb, n1, idx;
60 uint32_t code;
61 VLC_TYPE(*table)[2];
62
63 table_size = 1 << table_nb_bits;
64 table_index = vlc->table_size;
65 alloc_table(vlc, table_size);
66 table = &vlc->table[table_index];
67
68 for (i = 0; i < table_size; i++) {
69 table[i][1] = 0; /* bits */
70 table[i][0] = -1; /* codes */
71 }
72
73 /* map codes and compute auxiliary table sizes */
74 for (i = 0; i < nb_codes; i++) {
75 GET_DATA(n, bits, i, 1);
76 /* we accept tables with holes */
77 n -= n_prefix;
78 if (n <= 0)
79 continue;
80 GET_DATA(code, codes, i, codes_size);
81 /* if code matches the prefix, it is in the table */
82 if ((code >> n) != code_prefix)
83 continue;
84 if (n <= table_nb_bits) {
85 /* no need to add another table */
86 j = (code << (table_nb_bits - n)) & (table_size - 1);
87 nb = 1 << (table_nb_bits - n);
88 for (k = 0; k < nb; k++) {
89 assert(table[j][1] == 0); /* incorrect code */
90 table[j][1] = n; /* bits */
91 table[j][0] = i;
92 j++;
93 }
94 } else {
95 n -= table_nb_bits;
96 j = (code >> n) & ((1 << table_nb_bits) - 1);
97 /* compute table size */
98 n1 = -table[j][1]; /* bits */
99 if (n > n1)
100 n1 = n;
101 table[j][1] = -n1; /* bits */
102 }
103 }
104
105 /* fill auxiliary tables recursively */
106 for (i = 0; i < table_size; i++) {
107 n = table[i][1]; /* bits */
108 if (n < 0) {
109 n = -n;
110 if (n > table_nb_bits) {
111 n = table_nb_bits;
112 table[i][1] = -n; /* bits */
113 }
114 idx = build_table(vlc, n, nb_codes, bits, codes,
115 codes_size, (code_prefix << table_nb_bits) | i,
116 n_prefix + table_nb_bits);
117 /* vlc->table might have changed */
118 table = &vlc->table[table_index];
119 table[i][0] = idx; /* code */
120 }
121 }
122 return table_index;
123 }
124
125 /**
126 * Build VLC decoding tables suitable for use with get_vlc().
127 *
128 * \param vlc The structure to be initialized.
129 * \param nb_bits Set the decoding table size (2^nb_bits) entries.
130 * \param nb_codes Number of vlc codes.
131 * \param bits Table which gives the size (in bits) of each vlc code.
132 * \param codes Table which gives the bit pattern of of each vlc code.
133 * \param codes_size The number of bytes of each entry of the \a codes tables.
134 *
135 * The bigger \a nb_bits is, the faster is the decoding. But it should not be
136 * too big to save memory and L1 cache. '9' is a good compromise.
137 *
138 * The wrap and size parameters allow to use any memory configuration and
139 * types (byte/word/long) to store the bits and codes tables.
140 */
141 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
142 const void *codes, int codes_size)
143 {
144 PARA_INFO_LOG("nb_codes: %d\n", nb_codes);
145 vlc->bits = nb_bits;
146 vlc->table = NULL;
147 vlc->table_allocated = 0;
148 vlc->table_size = 0;
149 build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
150 }
151
152 /**
153 * Deallocate all resources of a VLC table.
154 *
155 * \param vlc Pointer to an initialized vlc structure.
156 *
157 * The table given by \a vlc must have been initialized earlier via \ref
158 * init_vlc().
159 */
160 void free_vlc(struct vlc *vlc)
161 {
162 freep(&vlc->table);
163 }
164
165 /**
166 * Parse a vlc code.
167 *
168 * \param gbc The getbit context structure.
169 * \param table The vlc tables to use.
170 * \param bits The number of bits which will be read at once.
171 * \param max_depth The number of times \a bits bits must be read to completely
172 * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
173 *
174 * The \a bits parameter must be identical to the \a nb_bits value supplied to
175 * \ref init_vlc().
176 *
177 * \return The vlc code.
178 */
179 int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
180 int max_depth)
181 {
182 int n, idx, nb_bits, code;
183
184 idx = show_bits(gbc, bits);
185 code = table[idx][0];
186 n = table[idx][1];
187 if (max_depth > 1 && n < 0) {
188 skip_bits(gbc, bits);
189 nb_bits = -n;
190 idx = show_bits(gbc, nb_bits) + code;
191 code = table[idx][0];
192 n = table[idx][1];
193 if (max_depth > 2 && n < 0) {
194 skip_bits(gbc, nb_bits);
195 nb_bits = -n;
196 idx = show_bits(gbc, nb_bits) + code;
197 code = table[idx][0];
198 n = table[idx][1];
199 }
200 }
201 skip_bits(gbc, n);
202 return code >= 0? code : -E_VLC;
203 }