Simplify alloc_table().
[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 #define GET_DATA(v, table, i, wrap, size) \
31 {\
32 const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
33 switch (size) { \
34 case 1: \
35 v = *(const uint8_t *)ptr; \
36 break; \
37 case 2: \
38 v = *(const uint16_t *)ptr; \
39 break; \
40 default: \
41 v = *(const uint32_t *)ptr; \
42 break; \
43 } \
44 }
45
46 static void alloc_table(struct vlc *vlc, int size)
47 {
48 vlc->table_size += size;
49 if (vlc->table_size > vlc->table_allocated) {
50 vlc->table_allocated += (1 << vlc->bits);
51 vlc->table = para_realloc(vlc->table,
52 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
53 }
54 }
55
56 static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
57 const void *bits, const void *codes, int codes_wrap,
58 int codes_size, uint32_t code_prefix, int n_prefix)
59 {
60 int ret, i, j, k, n, table_size, table_index, nb, n1, idx, code_prefix2,
61 symbol;
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 /* first pass: map codes and compute auxillary table sizes */
76 for (i = 0; i < nb_codes; i++) {
77 GET_DATA(n, bits, i, 1, 1);
78 GET_DATA(code, codes, i, codes_wrap, codes_size);
79 /* we accept tables with holes */
80 if (n <= 0)
81 continue;
82 symbol = i;
83 /* if code matches the prefix, it is in the table */
84 n -= n_prefix;
85 code_prefix2 = code >> n;
86 if (n > 0 && code_prefix2 == code_prefix) {
87 if (n <= table_nb_bits) {
88 /* no need to add another table */
89 j = (code << (table_nb_bits - n)) & (table_size - 1);
90 nb = 1 << (table_nb_bits - n);
91 for (k = 0; k < nb; k++) {
92 if (table[j][1] /* bits */ != 0)
93 return -E_BAD_CODES;
94 table[j][1] = n; //bits
95 table[j][0] = symbol;
96 j++;
97 }
98 } else {
99 n -= table_nb_bits;
100 j = (code >> n) & ((1 << table_nb_bits) - 1);
101 /* compute table size */
102 n1 = -table[j][1]; //bits
103 if (n > n1)
104 n1 = n;
105 table[j][1] = -n1; //bits
106 }
107 }
108 }
109
110 /* second pass : fill auxillary 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 ret = build_table(vlc, n, nb_codes,
120 bits, codes, codes_wrap, codes_size,
121 (code_prefix << table_nb_bits) | i,
122 n_prefix + table_nb_bits);
123 if (ret < 0)
124 return ret;
125 idx = ret;
126 /* note: realloc has been done, so reload tables */
127 table = &vlc->table[table_index];
128 table[i][0] = idx; //code
129 }
130 }
131 return table_index;
132 }
133
134 /**
135 * Build VLC decoding tables suitable for use with get_vlc().
136 *
137 * \param nb_bits Set the decoding table size (2^nb_bits)
138 * entries. The bigger it is, the faster is the decoding. But
139 * it should not be too big to save memory and L1 cache. '9'
140 * is a good compromise.
141 *
142 * \param nb_codes Number of vlcs codes.
143 *
144 * \param bits Table which gives the size (in bits) of each
145 * vlc code.
146 *
147 * \param codes Table which gives the bit pattern of of each
148 * vlc code.
149 *
150 * \param codes_wrap The number of bytes between each entry of the
151 * 'codes' tables.
152 *
153 * \param codes_size The number of bytes of each entry of the
154 * 'codes' tables.
155 *
156 * The wrap and size parameters allow to use any memory configuration and
157 * types (byte/word/long) to store the bits and codes tables.
158 */
159 int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
160 const void *bits, const void *codes, int codes_wrap,
161 int codes_size)
162 {
163 int ret;
164
165 PARA_INFO_LOG("nb_codes=%d\n", nb_codes);
166 vlc->bits = nb_bits;
167 vlc->table = NULL;
168 vlc->table_allocated = 0;
169 vlc->table_size = 0;
170 ret = build_table(vlc, nb_bits, nb_codes, bits,
171 codes, codes_wrap, codes_size, 0, 0);
172 if (ret < 0)
173 freep(&vlc->table);
174 return ret;
175 }
176
177 void free_vlc(struct vlc *vlc)
178 {
179 freep(&vlc->table);
180 }