bitstream: Remove pointless variable "code_prefix2".
[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 /**
15 * \file bitstream.c Bitstream API.
16 */
17
18 #include <stdlib.h>
19 #include <inttypes.h>
20 #include <stdio.h>
21 #include <string.h>
22 #include <regex.h>
23
24 #include "para.h"
25 #include "error.h"
26 #include "string.h"
27 #include "wma.h"
28 #include "bitstream.h"
29
30 /** Read an 8, 16, or 32 bit entity from a VLC table. */
31 #define GET_DATA(v, table, i, size) \
32 {\
33 const uint8_t *ptr = (const uint8_t *)table + i * size; \
34 switch (size) { \
35 case 1: \
36 v = *(const uint8_t *)ptr; \
37 break; \
38 case 2: \
39 v = *(const uint16_t *)ptr; \
40 break; \
41 default: \
42 v = *(const uint32_t *)ptr; \
43 break; \
44 } \
45 }
46
47 static void alloc_table(struct vlc *vlc, int size)
48 {
49 vlc->table_size += size;
50 if (vlc->table_size > vlc->table_allocated) {
51 vlc->table_allocated += (1 << vlc->bits);
52 vlc->table = para_realloc(vlc->table,
53 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
54 }
55 }
56
57 static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
58 const void *bits, const void *codes, int codes_size,
59 uint32_t code_prefix, int n_prefix)
60 {
61 int i, j, k, n, table_size, table_index, nb, n1, idx;
62 uint32_t code;
63 VLC_TYPE(*table)[2];
64
65 table_size = 1 << table_nb_bits;
66 table_index = vlc->table_size;
67 alloc_table(vlc, table_size);
68 table = &vlc->table[table_index];
69
70 for (i = 0; i < table_size; i++) {
71 table[i][1] = 0; /* bits */
72 table[i][0] = -1; /* codes */
73 }
74
75 /* map codes and compute auxiliary table sizes */
76 for (i = 0; i < nb_codes; i++) {
77 GET_DATA(n, bits, i, 1);
78 /* we accept tables with holes */
79 n -= n_prefix;
80 if (n <= 0)
81 continue;
82 GET_DATA(code, codes, i, codes_size);
83 /* if code matches the prefix, it is in the table */
84 if ((code >> n) != code_prefix)
85 continue;
86 if (n <= table_nb_bits) {
87 /* no need to add another table */
88 j = (code << (table_nb_bits - n)) & (table_size - 1);
89 nb = 1 << (table_nb_bits - n);
90 for (k = 0; k < nb; k++) {
91 if (table[j][1] /* bits */ != 0) {
92 PARA_EMERG_LOG("incorrect code\n");
93 exit(EXIT_FAILURE);
94 }
95 table[j][1] = n; /* bits */
96 table[j][0] = i;
97 j++;
98 }
99 } else {
100 n -= table_nb_bits;
101 j = (code >> n) & ((1 << table_nb_bits) - 1);
102 /* compute table size */
103 n1 = -table[j][1]; /* bits */
104 if (n > n1)
105 n1 = n;
106 table[j][1] = -n1; /* bits */
107 }
108 }
109
110 /* fill auxiliary tables recursively */
111 for (i = 0; i < table_size; i++) {
112 n = table[i][1]; /* bits */
113 if (n < 0) {
114 n = -n;
115 if (n > table_nb_bits) {
116 n = table_nb_bits;
117 table[i][1] = -n; /* bits */
118 }
119 idx = build_table(vlc, n, nb_codes, bits, codes,
120 codes_size, (code_prefix << table_nb_bits) | i,
121 n_prefix + table_nb_bits);
122 /* vlc->table might have changed */
123 table = &vlc->table[table_index];
124 table[i][0] = idx; /* code */
125 }
126 }
127 return table_index;
128 }
129
130 /**
131 * Build VLC decoding tables suitable for use with get_vlc().
132 *
133 * \param vlc The structure to be initialized.
134 *
135 * \param nb_bits Set the decoding table size (2^nb_bits) entries. The bigger
136 * it is, the faster is the decoding. But it should not be too big to save
137 * memory and L1 cache. '9' is a good compromise.
138 *
139 * \param nb_codes Number of vlcs codes.
140 *
141 * \param bits Table which gives the size (in bits) of each vlc code.
142 *
143 * \param codes Table which gives the bit pattern of of each vlc code.
144 *
145 * \param codes_size The number of bytes of each entry of the \a codes tables.
146 *
147 * The wrap and size parameters allow to use any memory configuration and
148 * types (byte/word/long) to store the bits and codes tables.
149 */
150 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
151 const void *codes, int codes_size)
152 {
153 PARA_INFO_LOG("nb_codes: %d\n", nb_codes);
154 vlc->bits = nb_bits;
155 vlc->table = NULL;
156 vlc->table_allocated = 0;
157 vlc->table_size = 0;
158 build_table(vlc, nb_bits, nb_codes, bits, codes, codes_size, 0, 0);
159 }
160
161 /**
162 * Deallocate all resources of a VLC table.
163 *
164 * \param vlc Pointer to an initialized vlc structure.
165 *
166 * The table given by \a vlc must have been initialized earlier via \ref
167 * init_vlc().
168 */
169 void free_vlc(struct vlc *vlc)
170 {
171 freep(&vlc->table);
172 }
173
174 /**
175 * Parse a vlc code.
176 *
177 * \param gbc The getbit context structure.
178 *
179 * \param table The vlc tables to use.
180 *
181 * \param bits The number of bits which will be read at once, must be
182 * identical to nb_bits in init_vlc().
183 *
184 * \param max_depth The number of times bits bits must be read to completely
185 * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
186 *
187 * \return The vlc code.
188 */
189 int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
190 int max_depth)
191 {
192 int n, idx, nb_bits, code;
193
194 idx = show_bits(gbc, bits);
195 code = table[idx][0];
196 n = table[idx][1];
197 if (max_depth > 1 && n < 0) {
198 skip_bits(gbc, bits);
199 nb_bits = -n;
200 idx = show_bits(gbc, nb_bits) + code;
201 code = table[idx][0];
202 n = table[idx][1];
203 if (max_depth > 2 && n < 0) {
204 skip_bits(gbc, nb_bits);
205 nb_bits = -n;
206 idx = show_bits(gbc, nb_bits) + code;
207 code = table[idx][0];
208 n = table[idx][1];
209 }
210 }
211 skip_bits(gbc, n);
212 return code >= 0? code : -E_VLC;
213 }