Avoid negative shifts in build_table()
[libav.git] / libavcodec / bitstream.c
1 /*
2 * Common bit i/o utils
3 * Copyright (c) 2000, 2001 Fabrice Bellard
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5 *
6 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
7 *
8 * This file is part of FFmpeg.
9 *
10 * FFmpeg is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU Lesser General Public
12 * License as published by the Free Software Foundation; either
13 * version 2.1 of the License, or (at your option) any later version.
14 *
15 * FFmpeg is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * Lesser General Public License for more details.
19 *
20 * You should have received a copy of the GNU Lesser General Public
21 * License along with FFmpeg; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 */
24
25 /**
26 * @file libavcodec/bitstream.c
27 * bitstream api.
28 */
29
30 #include "avcodec.h"
31 #include "get_bits.h"
32 #include "put_bits.h"
33
34 const uint8_t ff_log2_run[32]={
35 0, 0, 0, 0, 1, 1, 1, 1,
36 2, 2, 2, 2, 3, 3, 3, 3,
37 4, 4, 5, 5, 6, 6, 7, 7,
38 8, 9,10,11,12,13,14,15
39 };
40
41 void align_put_bits(PutBitContext *s)
42 {
43 #ifdef ALT_BITSTREAM_WRITER
44 put_bits(s,( - s->index) & 7,0);
45 #else
46 put_bits(s,s->bit_left & 7,0);
47 #endif
48 }
49
50 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
51 {
52 while(*string){
53 put_bits(pb, 8, *string);
54 string++;
55 }
56 if(terminate_string)
57 put_bits(pb, 8, 0);
58 }
59
60 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
61 {
62 int words= length>>4;
63 int bits= length&15;
64 int i;
65
66 if(length==0) return;
67
68 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
69 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
70 }else{
71 for(i=0; put_bits_count(pb)&31; i++)
72 put_bits(pb, 8, src[i]);
73 flush_put_bits(pb);
74 memcpy(put_bits_ptr(pb), src+i, 2*words-i);
75 skip_put_bytes(pb, 2*words-i);
76 }
77
78 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
79 }
80
81 /* VLC decoding */
82
83 //#define DEBUG_VLC
84
85 #define GET_DATA(v, table, i, wrap, size) \
86 {\
87 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
88 switch(size) {\
89 case 1:\
90 v = *(const uint8_t *)ptr;\
91 break;\
92 case 2:\
93 v = *(const uint16_t *)ptr;\
94 break;\
95 default:\
96 v = *(const uint32_t *)ptr;\
97 break;\
98 }\
99 }
100
101
102 static int alloc_table(VLC *vlc, int size, int use_static)
103 {
104 int index;
105 index = vlc->table_size;
106 vlc->table_size += size;
107 if (vlc->table_size > vlc->table_allocated) {
108 if(use_static)
109 abort(); //cant do anything, init_vlc() is used with too little memory
110 vlc->table_allocated += (1 << vlc->bits);
111 vlc->table = av_realloc(vlc->table,
112 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
113 if (!vlc->table)
114 return -1;
115 }
116 return index;
117 }
118
119 static int build_table(VLC *vlc, int table_nb_bits,
120 int nb_codes,
121 const void *bits, int bits_wrap, int bits_size,
122 const void *codes, int codes_wrap, int codes_size,
123 const void *symbols, int symbols_wrap, int symbols_size,
124 uint32_t code_prefix, int n_prefix, int flags)
125 {
126 int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
127 uint32_t code;
128 VLC_TYPE (*table)[2];
129
130 table_size = 1 << table_nb_bits;
131 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
132 #ifdef DEBUG_VLC
133 av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
134 table_index, table_size, code_prefix, n_prefix);
135 #endif
136 if (table_index < 0)
137 return -1;
138 table = &vlc->table[table_index];
139
140 for(i=0;i<table_size;i++) {
141 table[i][1] = 0; //bits
142 table[i][0] = -1; //codes
143 }
144
145 /* first pass: map codes and compute auxillary table sizes */
146 for(i=0;i<nb_codes;i++) {
147 GET_DATA(n, bits, i, bits_wrap, bits_size);
148 GET_DATA(code, codes, i, codes_wrap, codes_size);
149 /* we accept tables with holes */
150 if (n <= 0)
151 continue;
152 if (!symbols)
153 symbol = i;
154 else
155 GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
156 #if defined(DEBUG_VLC) && 0
157 av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
158 #endif
159 /* if code matches the prefix, it is in the table */
160 n -= n_prefix;
161 if (n > 0) {
162 if(flags & INIT_VLC_LE)
163 code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
164 else
165 code_prefix2= code >> n;
166 if (code_prefix2 == code_prefix) {
167 if (n <= table_nb_bits) {
168 /* no need to add another table */
169 j = (code << (table_nb_bits - n)) & (table_size - 1);
170 nb = 1 << (table_nb_bits - n);
171 for(k=0;k<nb;k++) {
172 if(flags & INIT_VLC_LE)
173 j = (code >> n_prefix) + (k<<n);
174 #ifdef DEBUG_VLC
175 av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
176 j, i, n);
177 #endif
178 if (table[j][1] /*bits*/ != 0) {
179 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
180 return -1;
181 }
182 table[j][1] = n; //bits
183 table[j][0] = symbol;
184 j++;
185 }
186 } else {
187 n -= table_nb_bits;
188 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
189 #ifdef DEBUG_VLC
190 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
191 j, n);
192 #endif
193 /* compute table size */
194 n1 = -table[j][1]; //bits
195 if (n > n1)
196 n1 = n;
197 table[j][1] = -n1; //bits
198 }
199 }
200 }
201 }
202
203 /* second pass : fill auxillary tables recursively */
204 for(i=0;i<table_size;i++) {
205 n = table[i][1]; //bits
206 if (n < 0) {
207 n = -n;
208 if (n > table_nb_bits) {
209 n = table_nb_bits;
210 table[i][1] = -n; //bits
211 }
212 index = build_table(vlc, n, nb_codes,
213 bits, bits_wrap, bits_size,
214 codes, codes_wrap, codes_size,
215 symbols, symbols_wrap, symbols_size,
216 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
217 n_prefix + table_nb_bits, flags);
218 if (index < 0)
219 return -1;
220 /* note: realloc has been done, so reload tables */
221 table = &vlc->table[table_index];
222 table[i][0] = index; //code
223 }
224 }
225 return table_index;
226 }
227
228
229 /* Build VLC decoding tables suitable for use with get_vlc().
230
231 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
232 bigger it is, the faster is the decoding. But it should not be too
233 big to save memory and L1 cache. '9' is a good compromise.
234
235 'nb_codes' : number of vlcs codes
236
237 'bits' : table which gives the size (in bits) of each vlc code.
238
239 'codes' : table which gives the bit pattern of of each vlc code.
240
241 'symbols' : table which gives the values to be returned from get_vlc().
242
243 'xxx_wrap' : give the number of bytes between each entry of the
244 'bits' or 'codes' tables.
245
246 'xxx_size' : gives the number of bytes of each entry of the 'bits'
247 or 'codes' tables.
248
249 'wrap' and 'size' allows to use any memory configuration and types
250 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
251
252 'use_static' should be set to 1 for tables, which should be freed
253 with av_free_static(), 0 if free_vlc() will be used.
254 */
255 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
256 const void *bits, int bits_wrap, int bits_size,
257 const void *codes, int codes_wrap, int codes_size,
258 const void *symbols, int symbols_wrap, int symbols_size,
259 int flags)
260 {
261 vlc->bits = nb_bits;
262 if(flags & INIT_VLC_USE_NEW_STATIC){
263 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
264 return 0;
265 }else if(vlc->table_size){
266 abort(); // fatal error, we are called on a partially initialized table
267 }
268 }else {
269 vlc->table = NULL;
270 vlc->table_allocated = 0;
271 vlc->table_size = 0;
272 }
273
274 #ifdef DEBUG_VLC
275 av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
276 #endif
277
278 if (build_table(vlc, nb_bits, nb_codes,
279 bits, bits_wrap, bits_size,
280 codes, codes_wrap, codes_size,
281 symbols, symbols_wrap, symbols_size,
282 0, 0, flags) < 0) {
283 av_freep(&vlc->table);
284 return -1;
285 }
286 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
287 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
288 return 0;
289 }
290
291
292 void free_vlc(VLC *vlc)
293 {
294 av_freep(&vlc->table);
295 }
296