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ffmpeg/libavcodec/vlc.c

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/*
* API for creating VLC trees
* Copyright (c) 2000, 2001 Fabrice Bellard
* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2010 Loren Merritt
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <inttypes.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "libavutil/attributes.h"
#include "libavutil/avassert.h"
#include "libavutil/error.h"
#include "libavutil/internal.h"
#include "libavutil/log.h"
#include "libavutil/macros.h"
#include "libavutil/mem.h"
#include "libavutil/qsort.h"
#include "libavutil/reverse.h"
#include "vlc.h"
#define GET_DATA(v, table, i, wrap, size) \
{ \
const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
switch(size) { \
case 1: \
v = *(const uint8_t *)ptr; \
break; \
case 2: \
v = *(const uint16_t *)ptr; \
break; \
case 4: \
default: \
av_assert1(size == 4); \
v = *(const uint32_t *)ptr; \
break; \
} \
}
static int alloc_table(VLC *vlc, int size, int use_static)
{
int index = vlc->table_size;
vlc->table_size += size;
if (vlc->table_size > vlc->table_allocated) {
if (use_static)
abort(); // cannot do anything, init_vlc() is used with too little memory
vlc->table_allocated += (1 << vlc->bits);
vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(*vlc->table));
if (!vlc->table) {
vlc->table_allocated = 0;
vlc->table_size = 0;
return AVERROR(ENOMEM);
}
memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(*vlc->table) << vlc->bits);
}
return index;
}
#define LOCALBUF_ELEMS 1500 // the maximum currently needed is 1296 by rv34
static av_always_inline uint32_t bitswap_32(uint32_t x)
{
return (uint32_t)ff_reverse[ x & 0xFF] << 24 |
(uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |
(uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |
(uint32_t)ff_reverse[ x >> 24];
}
typedef struct VLCcode {
uint8_t bits;
VLCBaseType symbol;
/** codeword, with the first bit-to-be-read in the msb
* (even if intended for a little-endian bitstream reader) */
uint32_t code;
} VLCcode;
static int vlc_common_init(VLC *vlc, int nb_bits, int nb_codes,
VLCcode **buf, int flags)
{
vlc->bits = nb_bits;
vlc->table_size = 0;
if (flags & INIT_VLC_USE_NEW_STATIC) {
av_assert0(nb_codes <= LOCALBUF_ELEMS);
} else {
vlc->table = NULL;
vlc->table_allocated = 0;
}
if (nb_codes > LOCALBUF_ELEMS) {
*buf = av_malloc_array(nb_codes, sizeof(VLCcode));
if (!*buf)
return AVERROR(ENOMEM);
}
return 0;
}
static int compare_vlcspec(const void *a, const void *b)
{
const VLCcode *sa = a, *sb = b;
return (sa->code >> 1) - (sb->code >> 1);
}
/**
* Build VLC decoding tables suitable for use with get_vlc().
*
* @param vlc the context to be initialized
*
* @param table_nb_bits max length of vlc codes to store directly in this table
* (Longer codes are delegated to subtables.)
*
* @param nb_codes number of elements in codes[]
*
* @param codes descriptions of the vlc codes
* These must be ordered such that codes going into the same subtable are contiguous.
* Sorting by VLCcode.code is sufficient, though not necessary.
*/
static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
VLCcode *codes, int flags)
{
int table_size, table_index;
VLCElem *table;
if (table_nb_bits > 30)
return AVERROR(EINVAL);
table_size = 1 << table_nb_bits;
table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
if (table_index < 0)
return table_index;
table = &vlc->table[table_index];
/* first pass: map codes and compute auxiliary table sizes */
for (int i = 0; i < nb_codes; i++) {
int n = codes[i].bits;
uint32_t code = codes[i].code;
int symbol = codes[i].symbol;
ff_dlog(NULL, "i=%d n=%d code=0x%"PRIx32"\n", i, n, code);
if (n <= table_nb_bits) {
/* no need to add another table */
int j = code >> (32 - table_nb_bits);
int nb = 1 << (table_nb_bits - n);
int inc = 1;
if (flags & INIT_VLC_OUTPUT_LE) {
j = bitswap_32(code);
inc = 1 << n;
}
for (int k = 0; k < nb; k++) {
int bits = table[j].len;
int oldsym = table[j].sym;
ff_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
if ((bits || oldsym) && (bits != n || oldsym != symbol)) {
av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
return AVERROR_INVALIDDATA;
}
table[j].len = n;
table[j].sym = symbol;
j += inc;
}
} else {
/* fill auxiliary table recursively */
uint32_t code_prefix;
int index, subtable_bits, j, k;
n -= table_nb_bits;
code_prefix = code >> (32 - table_nb_bits);
subtable_bits = n;
codes[i].bits = n;
codes[i].code = code << table_nb_bits;
for (k = i + 1; k < nb_codes; k++) {
n = codes[k].bits - table_nb_bits;
if (n <= 0)
break;
code = codes[k].code;
if (code >> (32 - table_nb_bits) != code_prefix)
break;
codes[k].bits = n;
codes[k].code = code << table_nb_bits;
subtable_bits = FFMAX(subtable_bits, n);
}
subtable_bits = FFMIN(subtable_bits, table_nb_bits);
j = (flags & INIT_VLC_OUTPUT_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
table[j].len = -subtable_bits;
ff_dlog(NULL, "%4x: n=%d (subtable)\n",
j, codes[i].bits + table_nb_bits);
index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
if (index < 0)
return index;
/* note: realloc has been done, so reload tables */
table = &vlc->table[table_index];
table[j].sym = index;
if (table[j].sym != index) {
avpriv_request_sample(NULL, "strange codes");
return AVERROR_PATCHWELCOME;
}
i = k-1;
}
}
for (int i = 0; i < table_size; i++) {
if (table[i].len == 0)
table[i].sym = -1;
}
return table_index;
}
static int vlc_common_end(VLC *vlc, int nb_bits, int nb_codes, VLCcode *codes,
int flags, VLCcode localbuf[LOCALBUF_ELEMS])
{
int ret = build_table(vlc, nb_bits, nb_codes, codes, flags);
if (flags & INIT_VLC_USE_NEW_STATIC) {
if (vlc->table_size != vlc->table_allocated &&
!(flags & (INIT_VLC_STATIC_OVERLONG & ~INIT_VLC_USE_NEW_STATIC)))
av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
av_assert0(ret >= 0);
} else {
if (codes != localbuf)
av_free(codes);
if (ret < 0) {
av_freep(&vlc->table);
return ret;
}
}
return 0;
}
/* Build VLC decoding tables suitable for use with get_vlc().
'nb_bits' sets the decoding table size (2^nb_bits) entries. The
bigger it is, the faster is the decoding. But it should not be too
big to save memory and L1 cache. '9' is a good compromise.
'nb_codes' : number of vlcs codes
'bits' : table which gives the size (in bits) of each vlc code.
'codes' : table which gives the bit pattern of of each vlc code.
'symbols' : table which gives the values to be returned from get_vlc().
'xxx_wrap' : give the number of bytes between each entry of the
'bits' or 'codes' tables.
'xxx_size' : gives the number of bytes of each entry of the 'bits'
or 'codes' tables. Currently 1,2 and 4 are supported.
'wrap' and 'size' make it possible to use any memory configuration and types
(byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
*/
int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size,
const void *symbols, int symbols_wrap, int symbols_size,
int flags)
{
VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
int j, ret;
ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
if (ret < 0)
return ret;
av_assert0(symbols_size <= 2 || !symbols);
j = 0;
#define COPY(condition)\
for (int i = 0; i < nb_codes; i++) { \
unsigned len; \
GET_DATA(len, bits, i, bits_wrap, bits_size); \
if (!(condition)) \
continue; \
if (len > 3*nb_bits || len > 32) { \
av_log(NULL, AV_LOG_ERROR, "Too long VLC (%u) in init_vlc\n", len);\
if (buf != localbuf) \
av_free(buf); \
return AVERROR(EINVAL); \
} \
buf[j].bits = len; \
GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
if (buf[j].code >= (1LL<<buf[j].bits)) { \
av_log(NULL, AV_LOG_ERROR, "Invalid code %"PRIx32" for %d in " \
"init_vlc\n", buf[j].code, i); \
if (buf != localbuf) \
av_free(buf); \
return AVERROR(EINVAL); \
} \
if (flags & INIT_VLC_INPUT_LE) \
buf[j].code = bitswap_32(buf[j].code); \
else \
buf[j].code <<= 32 - buf[j].bits; \
if (symbols) \
GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
else \
buf[j].symbol = i; \
j++; \
}
COPY(len > nb_bits);
// qsort is the slowest part of init_vlc, and could probably be improved or avoided
AV_QSORT(buf, j, struct VLCcode, compare_vlcspec);
COPY(len && len <= nb_bits);
nb_codes = j;
return vlc_common_end(vlc, nb_bits, nb_codes, buf,
flags, localbuf);
}
int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
const int8_t *lens, int lens_wrap,
const void *symbols, int symbols_wrap, int symbols_size,
int offset, int flags, void *logctx)
{
VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
uint64_t code;
int ret, j, len_max = FFMIN(32, 3 * nb_bits);
ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
if (ret < 0)
return ret;
j = code = 0;
for (int i = 0; i < nb_codes; i++, lens += lens_wrap) {
int len = *lens;
if (len > 0) {
unsigned sym;
buf[j].bits = len;
if (symbols)
GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
else
sym = i;
buf[j].symbol = sym + offset;
buf[j++].code = code;
} else if (len < 0) {
len = -len;
} else
continue;
if (len > len_max || code & ((1U << (32 - len)) - 1)) {
av_log(logctx, AV_LOG_ERROR, "Invalid VLC (length %u)\n", len);
goto fail;
}
code += 1U << (32 - len);
if (code > UINT32_MAX + 1ULL) {
av_log(logctx, AV_LOG_ERROR, "Overdetermined VLC tree\n");
goto fail;
}
}
return vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
fail:
if (buf != localbuf)
av_free(buf);
return AVERROR_INVALIDDATA;
}
void ff_free_vlc(VLC *vlc)
{
av_freep(&vlc->table);
}
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