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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/intreadwrite.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, vlc_init() 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 & VLC_INIT_USE_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 & VLC_INIT_USE_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 & VLC_INIT_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 & VLC_INIT_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 & VLC_INIT_USE_STATIC) {
if (vlc->table_size != vlc->table_allocated &&
!(flags & (VLC_INIT_STATIC_OVERLONG & ~VLC_INIT_USE_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;
}
int ff_vlc_init_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 vlc_init\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 " \
"vlc_init\n", buf[j].code, i); \
if (buf != localbuf) \
av_free(buf); \
return AVERROR(EINVAL); \
} \
if (flags & VLC_INIT_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 vlc_init, 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_vlc_init_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;
}
static void add_level(VLC_MULTI_ELEM *table, const int nb_elems,
const int num, const int numbits,
const VLCcode *buf,
uint32_t curcode, int curlen,
int curlimit, int curlevel,
const int minlen, const int max,
unsigned* levelcnt, VLC_MULTI_ELEM *info)
{
if (nb_elems > 256 && curlevel > 2)
return; // No room
for (int i = num-1; i > max; i--) {
for (int j = 0; j < 2; j++) {
int newlimit, sym;
int t = j ? i-1 : i;
int l = buf[t].bits;
uint32_t code;
sym = buf[t].symbol;
if (l > curlimit)
return;
code = curcode + (buf[t].code >> curlen);
newlimit = curlimit - l;
l += curlen;
if (nb_elems>256) AV_WN16(info->val+2*curlevel, sym);
else info->val[curlevel] = sym&0xFF;
if (curlevel) { // let's not add single entries
uint32_t val = code >> (32 - numbits);
uint32_t nb = val + (1U << (numbits - l));
info->len = l;
info->num = curlevel+1;
for (; val < nb; val++)
AV_COPY64(table+val, info);
levelcnt[curlevel-1]++;
}
if (curlevel+1 < VLC_MULTI_MAX_SYMBOLS && newlimit >= minlen) {
add_level(table, nb_elems, num, numbits, buf,
code, l, newlimit, curlevel+1,
minlen, max, levelcnt, info);
}
}
}
}
static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
const int nb_elems, const int nb_codes, const int numbits,
VLCcode *buf, void *logctx)
{
int minbits, maxbits, max = nb_codes-1;
unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
VLC_MULTI_ELEM info = { { 0, }, 0, };
minbits = buf[nb_codes-1].bits;
maxbits = FFMIN(buf[0].bits, numbits);
while (max >= nb_codes/2) {
if (buf[max].bits+minbits > maxbits)
break;
max--;
}
for (int j = 0; j < 1<<numbits; j++) {
table[j].len = single->table[j].len;
table[j].num = single->table[j].len > 0 ? 1 : 0;
AV_WN16(table[j].val, single->table[j].sym);
}
add_level(table, nb_elems, nb_codes, numbits, buf,
0, 0, FFMIN(maxbits, numbits), 0, minbits, max, count, &info);
av_log(NULL, AV_LOG_DEBUG, "Joint: %d/%d/%d/%d/%d codes min=%ubits max=%u\n",
count[0], count[1], count[2], count[3], count[4], minbits, max);
return 0;
}
int ff_vlc_init_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
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;
multi->table = av_malloc(sizeof(*multi->table) << nb_bits);
if (!multi->table)
return AVERROR(ENOMEM);
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;
}
}
ret = vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
if (ret < 0)
goto fail;
return vlc_multi_gen(multi->table, vlc, nb_elems, j, nb_bits, buf, logctx);
fail:
if (buf != localbuf)
av_free(buf);
return AVERROR_INVALIDDATA;
}
void ff_vlc_free_multi(VLC_MULTI *vlc)
{
av_freep(&vlc->table);
}
void ff_vlc_free(VLC *vlc)
{
av_freep(&vlc->table);
}
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