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