/* * 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); }