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 FFmpeg.
10 *
11 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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[32]={
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
40};
41
42void align_put_bits(PutBitContext *s)
43{
44#ifdef ALT_BITSTREAM_WRITER
45    put_bits(s,(  - s->index) & 7,0);
46#else
47    put_bits(s,s->bit_left & 7,0);
48#endif
49}
50
51void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
52{
53    while(*string){
54        put_bits(pb, 8, *string);
55        string++;
56    }
57    if(terminate_string)
58        put_bits(pb, 8, 0);
59}
60
61void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
62{
63    int words= length>>4;
64    int bits= length&15;
65    int i;
66
67    if(length==0) return;
68
69    if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
70        for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
71    }else{
72        for(i=0; put_bits_count(pb)&31; i++)
73            put_bits(pb, 8, src[i]);
74        flush_put_bits(pb);
75        memcpy(put_bits_ptr(pb), src+i, 2*words-i);
76        skip_put_bytes(pb, 2*words-i);
77    }
78
79    put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
80}
81
82/* VLC decoding */
83
84//#define DEBUG_VLC
85
86#define GET_DATA(v, table, i, wrap, size) \
87{\
88    const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
89    switch(size) {\
90    case 1:\
91        v = *(const uint8_t *)ptr;\
92        break;\
93    case 2:\
94        v = *(const uint16_t *)ptr;\
95        break;\
96    default:\
97        v = *(const uint32_t *)ptr;\
98        break;\
99    }\
100}
101
102
103static int alloc_table(VLC *vlc, int size, int use_static)
104{
105    int index;
106    index = vlc->table_size;
107    vlc->table_size += size;
108    if (vlc->table_size > vlc->table_allocated) {
109        if(use_static)
110            abort(); //cant do anything, init_vlc() is used with too little memory
111        vlc->table_allocated += (1 << vlc->bits);
112        vlc->table = av_realloc(vlc->table,
113                                sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
114        if (!vlc->table)
115            return -1;
116    }
117    return index;
118}
119
120static av_always_inline uint32_t bitswap_32(uint32_t x) {
121    return av_reverse[x&0xFF]<<24
122         | av_reverse[(x>>8)&0xFF]<<16
123         | av_reverse[(x>>16)&0xFF]<<8
124         | av_reverse[x>>24];
125}
126
127typedef struct {
128    uint8_t bits;
129    uint16_t symbol;
130    /** codeword, with the first bit-to-be-read in the msb
131     * (even if intended for a little-endian bitstream reader) */
132    uint32_t code;
133} VLCcode;
134
135static int compare_vlcspec(const void *a, const void *b)
136{
137    const VLCcode *sa=a, *sb=b;
138    return (sa->code >> 1) - (sb->code >> 1);
139}
140
141/**
142 * Build VLC decoding tables suitable for use with get_vlc().
143 *
144 * @param vlc            the context to be initted
145 *
146 * @param table_nb_bits  max length of vlc codes to store directly in this table
147 *                       (Longer codes are delegated to subtables.)
148 *
149 * @param nb_codes       number of elements in codes[]
150 *
151 * @param codes          descriptions of the vlc codes
152 *                       These must be ordered such that codes going into the same subtable are contiguous.
153 *                       Sorting by VLCcode.code is sufficient, though not necessary.
154 */
155static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
156                       VLCcode *codes, int flags)
157{
158    int table_size, table_index, index, code_prefix, symbol, subtable_bits;
159    int i, j, k, n, nb, inc;
160    uint32_t code;
161    VLC_TYPE (*table)[2];
162
163    table_size = 1 << table_nb_bits;
164    table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
165#ifdef DEBUG_VLC
166    av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d\n",
167           table_index, table_size);
168#endif
169    if (table_index < 0)
170        return -1;
171    table = &vlc->table[table_index];
172
173    for (i = 0; i < table_size; i++) {
174        table[i][1] = 0; //bits
175        table[i][0] = -1; //codes
176    }
177
178    /* first pass: map codes and compute auxillary table sizes */
179    for (i = 0; i < nb_codes; i++) {
180        n = codes[i].bits;
181        code = codes[i].code;
182        symbol = codes[i].symbol;
183#if defined(DEBUG_VLC) && 0
184        av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
185#endif
186        if (n <= table_nb_bits) {
187            /* no need to add another table */
188            j = code >> (32 - table_nb_bits);
189            nb = 1 << (table_nb_bits - n);
190            inc = 1;
191            if (flags & INIT_VLC_LE) {
192                j = bitswap_32(code);
193                inc = 1 << n;
194            }
195            for (k = 0; k < nb; k++) {
196#ifdef DEBUG_VLC
197                av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
198                       j, i, n);
199#endif
200                if (table[j][1] /*bits*/ != 0) {
201                    av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
202                    return -1;
203                }
204                table[j][1] = n; //bits
205                table[j][0] = symbol;
206                j += inc;
207            }
208        } else {
209            /* fill auxiliary table recursively */
210            n -= table_nb_bits;
211            code_prefix = code >> (32 - table_nb_bits);
212            subtable_bits = n;
213            codes[i].bits = n;
214            codes[i].code = code << table_nb_bits;
215            for (k = i+1; k < nb_codes; k++) {
216                n = codes[k].bits - table_nb_bits;
217                if (n <= 0)
218                    break;
219                code = codes[k].code;
220                if (code >> (32 - table_nb_bits) != code_prefix)
221                    break;
222                codes[k].bits = n;
223                codes[k].code = code << table_nb_bits;
224                subtable_bits = FFMAX(subtable_bits, n);
225            }
226            subtable_bits = FFMIN(subtable_bits, table_nb_bits);
227            j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
228            table[j][1] = -subtable_bits;
229#ifdef DEBUG_VLC
230            av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
231                   j, codes[i].bits + table_nb_bits);
232#endif
233            index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
234            if (index < 0)
235                return -1;
236            /* note: realloc has been done, so reload tables */
237            table = &vlc->table[table_index];
238            table[j][0] = index; //code
239            i = k-1;
240        }
241    }
242    return table_index;
243}
244
245
246/* Build VLC decoding tables suitable for use with get_vlc().
247
248   'nb_bits' set thee decoding table size (2^nb_bits) entries. The
249   bigger it is, the faster is the decoding. But it should not be too
250   big to save memory and L1 cache. '9' is a good compromise.
251
252   'nb_codes' : number of vlcs codes
253
254   'bits' : table which gives the size (in bits) of each vlc code.
255
256   'codes' : table which gives the bit pattern of of each vlc code.
257
258   'symbols' : table which gives the values to be returned from get_vlc().
259
260   'xxx_wrap' : give the number of bytes between each entry of the
261   'bits' or 'codes' tables.
262
263   'xxx_size' : gives the number of bytes of each entry of the 'bits'
264   or 'codes' tables.
265
266   'wrap' and 'size' allows to use any memory configuration and types
267   (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
268
269   'use_static' should be set to 1 for tables, which should be freed
270   with av_free_static(), 0 if free_vlc() will be used.
271*/
272int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
273             const void *bits, int bits_wrap, int bits_size,
274             const void *codes, int codes_wrap, int codes_size,
275             const void *symbols, int symbols_wrap, int symbols_size,
276             int flags)
277{
278    VLCcode buf[nb_codes];
279    int i, j;
280
281    vlc->bits = nb_bits;
282    if(flags & INIT_VLC_USE_NEW_STATIC){
283        if(vlc->table_size && vlc->table_size == vlc->table_allocated){
284            return 0;
285        }else if(vlc->table_size){
286            abort(); // fatal error, we are called on a partially initialized table
287        }
288    }else {
289        vlc->table = NULL;
290        vlc->table_allocated = 0;
291        vlc->table_size = 0;
292    }
293
294#ifdef DEBUG_VLC
295    av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
296#endif
297
298    assert(symbols_size <= 2 || !symbols);
299    j = 0;
300#define COPY(condition)\
301    for (i = 0; i < nb_codes; i++) {\
302        GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\
303        if (!(condition))\
304            continue;\
305        GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
306        if (flags & INIT_VLC_LE)\
307            buf[j].code = bitswap_32(buf[j].code);\
308        else\
309            buf[j].code <<= 32 - buf[j].bits;\
310        if (symbols)\
311            GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
312        else\
313            buf[j].symbol = i;\
314        j++;\
315    }
316    COPY(buf[j].bits > nb_bits);
317    // qsort is the slowest part of init_vlc, and could probably be improved or avoided
318    qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
319    COPY(buf[j].bits && buf[j].bits <= nb_bits);
320    nb_codes = j;
321
322    if (build_table(vlc, nb_bits, nb_codes, buf, flags) < 0) {
323        av_freep(&vlc->table);
324        return -1;
325    }
326    if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
327        av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
328    return 0;
329}
330
331
332void free_vlc(VLC *vlc)
333{
334    av_freep(&vlc->table);
335}
336
337