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 * Copyright (c) 2010 Loren Merritt 6 * 7 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at> 8 * 9 * This file is part of Libav. 10 * 11 * Libav is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU Lesser General Public 13 * License as published by the Free Software Foundation; either 14 * version 2.1 of the License, or (at your option) any later version. 15 * 16 * Libav is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 19 * Lesser General Public License for more details. 20 * 21 * You should have received a copy of the GNU Lesser General Public 22 * License along with Libav; if not, write to the Free Software 23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 24 */ 25 26/** 27 * @file 28 * bitstream api. 29 */ 30 31#include "avcodec.h" 32#include "get_bits.h" 33#include "put_bits.h" 34 35const uint8_t ff_log2_run[41]={ 36 0, 0, 0, 0, 1, 1, 1, 1, 37 2, 2, 2, 2, 3, 3, 3, 3, 38 4, 4, 5, 5, 6, 6, 7, 7, 39 8, 9,10,11,12,13,14,15, 4016,17,18,19,20,21,22,23, 4124, 42}; 43 44void avpriv_align_put_bits(PutBitContext *s) 45{ 46 put_bits(s,s->bit_left & 7,0); 47} 48 49void ff_put_string(PutBitContext *pb, const char *string, int terminate_string) 50{ 51 while(*string){ 52 put_bits(pb, 8, *string); 53 string++; 54 } 55 if(terminate_string) 56 put_bits(pb, 8, 0); 57} 58 59void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length) 60{ 61 int words= length>>4; 62 int bits= length&15; 63 int i; 64 65 if(length==0) return; 66 67 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){ 68 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i)); 69 }else{ 70 for(i=0; put_bits_count(pb)&31; i++) 71 put_bits(pb, 8, src[i]); 72 flush_put_bits(pb); 73 memcpy(put_bits_ptr(pb), src+i, 2*words-i); 74 skip_put_bytes(pb, 2*words-i); 75 } 76 77 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits)); 78} 79 80/* VLC decoding */ 81 82#define GET_DATA(v, table, i, wrap, size) \ 83{\ 84 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\ 85 switch(size) {\ 86 case 1:\ 87 v = *(const uint8_t *)ptr;\ 88 break;\ 89 case 2:\ 90 v = *(const uint16_t *)ptr;\ 91 break;\ 92 default:\ 93 v = *(const uint32_t *)ptr;\ 94 break;\ 95 }\ 96} 97 98 99static int alloc_table(VLC *vlc, int size, int use_static) 100{ 101 int index; 102 index = vlc->table_size; 103 vlc->table_size += size; 104 if (vlc->table_size > vlc->table_allocated) { 105 if(use_static) 106 abort(); // cannot do anything, init_vlc() is used with too little memory 107 vlc->table_allocated += (1 << vlc->bits); 108 vlc->table = av_realloc(vlc->table, 109 sizeof(VLC_TYPE) * 2 * vlc->table_allocated); 110 if (!vlc->table) 111 return -1; 112 } 113 return index; 114} 115 116static av_always_inline uint32_t bitswap_32(uint32_t x) { 117 return (uint32_t)av_reverse[x&0xFF]<<24 118 | (uint32_t)av_reverse[(x>>8)&0xFF]<<16 119 | (uint32_t)av_reverse[(x>>16)&0xFF]<<8 120 | (uint32_t)av_reverse[x>>24]; 121} 122 123typedef struct { 124 uint8_t bits; 125 uint16_t symbol; 126 /** codeword, with the first bit-to-be-read in the msb 127 * (even if intended for a little-endian bitstream reader) */ 128 uint32_t code; 129} VLCcode; 130 131static int compare_vlcspec(const void *a, const void *b) 132{ 133 const VLCcode *sa=a, *sb=b; 134 return (sa->code >> 1) - (sb->code >> 1); 135} 136 137/** 138 * Build VLC decoding tables suitable for use with get_vlc(). 139 * 140 * @param vlc the context to be initted 141 * 142 * @param table_nb_bits max length of vlc codes to store directly in this table 143 * (Longer codes are delegated to subtables.) 144 * 145 * @param nb_codes number of elements in codes[] 146 * 147 * @param codes descriptions of the vlc codes 148 * These must be ordered such that codes going into the same subtable are contiguous. 149 * Sorting by VLCcode.code is sufficient, though not necessary. 150 */ 151static int build_table(VLC *vlc, int table_nb_bits, int nb_codes, 152 VLCcode *codes, int flags) 153{ 154 int table_size, table_index, index, code_prefix, symbol, subtable_bits; 155 int i, j, k, n, nb, inc; 156 uint32_t code; 157 VLC_TYPE (*table)[2]; 158 159 table_size = 1 << table_nb_bits; 160 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC); 161 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size); 162 if (table_index < 0) 163 return -1; 164 table = &vlc->table[table_index]; 165 166 for (i = 0; i < table_size; i++) { 167 table[i][1] = 0; //bits 168 table[i][0] = -1; //codes 169 } 170 171 /* first pass: map codes and compute auxillary table sizes */ 172 for (i = 0; i < nb_codes; i++) { 173 n = codes[i].bits; 174 code = codes[i].code; 175 symbol = codes[i].symbol; 176 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code); 177 if (n <= table_nb_bits) { 178 /* no need to add another table */ 179 j = code >> (32 - table_nb_bits); 180 nb = 1 << (table_nb_bits - n); 181 inc = 1; 182 if (flags & INIT_VLC_LE) { 183 j = bitswap_32(code); 184 inc = 1 << n; 185 } 186 for (k = 0; k < nb; k++) { 187 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n); 188 if (table[j][1] /*bits*/ != 0) { 189 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n"); 190 return -1; 191 } 192 table[j][1] = n; //bits 193 table[j][0] = symbol; 194 j += inc; 195 } 196 } else { 197 /* fill auxiliary table recursively */ 198 n -= table_nb_bits; 199 code_prefix = code >> (32 - table_nb_bits); 200 subtable_bits = n; 201 codes[i].bits = n; 202 codes[i].code = code << table_nb_bits; 203 for (k = i+1; k < nb_codes; k++) { 204 n = codes[k].bits - table_nb_bits; 205 if (n <= 0) 206 break; 207 code = codes[k].code; 208 if (code >> (32 - table_nb_bits) != code_prefix) 209 break; 210 codes[k].bits = n; 211 codes[k].code = code << table_nb_bits; 212 subtable_bits = FFMAX(subtable_bits, n); 213 } 214 subtable_bits = FFMIN(subtable_bits, table_nb_bits); 215 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix; 216 table[j][1] = -subtable_bits; 217 av_dlog(NULL, "%4x: n=%d (subtable)\n", 218 j, codes[i].bits + table_nb_bits); 219 index = build_table(vlc, subtable_bits, k-i, codes+i, flags); 220 if (index < 0) 221 return -1; 222 /* note: realloc has been done, so reload tables */ 223 table = &vlc->table[table_index]; 224 table[j][0] = index; //code 225 i = k-1; 226 } 227 } 228 return table_index; 229} 230 231 232/* Build VLC decoding tables suitable for use with get_vlc(). 233 234 'nb_bits' set thee decoding table size (2^nb_bits) entries. The 235 bigger it is, the faster is the decoding. But it should not be too 236 big to save memory and L1 cache. '9' is a good compromise. 237 238 'nb_codes' : number of vlcs codes 239 240 'bits' : table which gives the size (in bits) of each vlc code. 241 242 'codes' : table which gives the bit pattern of of each vlc code. 243 244 'symbols' : table which gives the values to be returned from get_vlc(). 245 246 'xxx_wrap' : give the number of bytes between each entry of the 247 'bits' or 'codes' tables. 248 249 'xxx_size' : gives the number of bytes of each entry of the 'bits' 250 or 'codes' tables. 251 252 'wrap' and 'size' allows to use any memory configuration and types 253 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables. 254 255 'use_static' should be set to 1 for tables, which should be freed 256 with av_free_static(), 0 if ff_free_vlc() will be used. 257*/ 258int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes, 259 const void *bits, int bits_wrap, int bits_size, 260 const void *codes, int codes_wrap, int codes_size, 261 const void *symbols, int symbols_wrap, int symbols_size, 262 int flags) 263{ 264 VLCcode *buf; 265 int i, j, ret; 266 267 vlc->bits = nb_bits; 268 if(flags & INIT_VLC_USE_NEW_STATIC){ 269 if(vlc->table_size && vlc->table_size == vlc->table_allocated){ 270 return 0; 271 }else if(vlc->table_size){ 272 abort(); // fatal error, we are called on a partially initialized table 273 } 274 }else { 275 vlc->table = NULL; 276 vlc->table_allocated = 0; 277 vlc->table_size = 0; 278 } 279 280 av_dlog(NULL, "build table nb_codes=%d\n", nb_codes); 281 282 buf = av_malloc((nb_codes+1)*sizeof(VLCcode)); 283 284 assert(symbols_size <= 2 || !symbols); 285 j = 0; 286#define COPY(condition)\ 287 for (i = 0; i < nb_codes; i++) {\ 288 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\ 289 if (!(condition))\ 290 continue;\ 291 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\ 292 if (flags & INIT_VLC_LE)\ 293 buf[j].code = bitswap_32(buf[j].code);\ 294 else\ 295 buf[j].code <<= 32 - buf[j].bits;\ 296 if (symbols)\ 297 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\ 298 else\ 299 buf[j].symbol = i;\ 300 j++;\ 301 } 302 COPY(buf[j].bits > nb_bits); 303 // qsort is the slowest part of init_vlc, and could probably be improved or avoided 304 qsort(buf, j, sizeof(VLCcode), compare_vlcspec); 305 COPY(buf[j].bits && buf[j].bits <= nb_bits); 306 nb_codes = j; 307 308 ret = build_table(vlc, nb_bits, nb_codes, buf, flags); 309 310 av_free(buf); 311 if (ret < 0) { 312 av_freep(&vlc->table); 313 return -1; 314 } 315 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated) 316 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated); 317 return 0; 318} 319 320 321void ff_free_vlc(VLC *vlc) 322{ 323 av_freep(&vlc->table); 324} 325 326