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https://git.ffmpeg.org/ffmpeg.git
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edc50658d9
For lots of static VLCs, the number of bits is not read from VLC.bits, but rather a compile-constant that is hardcoded at the callsite of get_vlc2(). Only VLC.table is ever used and not using it directly is just an unnecessary indirection. This commit adds helper functions and macros to avoid the VLC structure when initializing VLC tables; there are 2x2 functions: Two choices for init_sparse or from_lengths and two choices for "overlong" initialization (as used when multiple VLCs are initialized that share the same underlying table). Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
329 lines
17 KiB
C
329 lines
17 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_VLC_H
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#define AVCODEC_VLC_H
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#include <stddef.h>
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#include <stdint.h>
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#include "libavutil/macros.h"
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#define VLC_MULTI_MAX_SYMBOLS 6
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// When changing this, be sure to also update tableprint_vlc.h accordingly.
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typedef int16_t VLCBaseType;
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typedef struct VLCElem {
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VLCBaseType sym, len;
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} VLCElem;
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typedef struct VLC {
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int bits;
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VLCElem *table;
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int table_size, table_allocated;
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} VLC;
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typedef struct VLC_MULTI_ELEM {
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uint8_t val[VLC_MULTI_MAX_SYMBOLS];
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int8_t len; // -31,32
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uint8_t num;
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} VLC_MULTI_ELEM;
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typedef struct VLC_MULTI {
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VLC_MULTI_ELEM *table;
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int table_size, table_allocated;
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} VLC_MULTI;
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typedef struct RL_VLC_ELEM {
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int16_t level;
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int8_t len;
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uint8_t run;
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} RL_VLC_ELEM;
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#define vlc_init(vlc, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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flags) \
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ff_vlc_init_sparse(vlc, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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NULL, 0, 0, flags)
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/**
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* Build VLC decoding tables suitable for use with get_vlc2().
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*
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* @param[in,out] vlc The VLC to be initialized; table and table_allocated
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* must have been set when initializing a static VLC,
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* otherwise this will be treated as uninitialized.
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* @param[in] nb_bits The number of bits to use for the VLC table;
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* higher values take up more memory and cache, but
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* allow to read codes with fewer reads.
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* Corresponds to the `bits` parameter of get_vlc2().
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* @param[in] nb_codes The number of provided bits, codes and (if supplied)
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* symbol entries.
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* @param[in] bits The lengths (in bits) of the codes. Entries > 0
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* correspond to valid codes; entries == 0 will be skipped.
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* @param[in] bits_wrap Stride (in bytes) of the bits table.
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* @param[in] codes_size Size of the bits. 1, 2 and 4 are supported.
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* @param[in] codes Table which gives the bit pattern of of each vlc code.
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* @param[in] codes_wrap Stride (in bytes) of the codes table.
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* @param[in] codes_size Size of the codes. 1, 2 and 4 are supported.
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* @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
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* when the corresponding code is encountered.
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* May be NULL, then 0, 1, 2, 3, 4,... will be used.
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* @param[in] symbols_wrap Stride (in bytes) of the symbols table.
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* @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
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* @param[in] flags A combination of the VLC_INIT_* flags.
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*
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* 'wrap' and 'size' make it possible to use any memory configuration and types
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* (byte/word/int) to store the 'bits', 'codes', and 'symbols' tables.
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*/
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int ff_vlc_init_sparse(VLC *vlc, int nb_bits, int nb_codes,
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const void *bits, int bits_wrap, int bits_size,
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const void *codes, int codes_wrap, int codes_size,
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const void *symbols, int symbols_wrap, int symbols_size,
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int flags);
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/**
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* Build VLC decoding tables suitable for use with get_vlc2()
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*
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* This function takes lengths and symbols and calculates the codes from them.
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* For this the input lengths and symbols have to be sorted according to "left
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* nodes in the corresponding tree first".
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*
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* @param[in,out] vlc The VLC to be initialized; table and table_allocated
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* must have been set when initializing a static VLC,
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* otherwise this will be treated as uninitialized.
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* @param[in] nb_bits The number of bits to use for the VLC table;
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* higher values take up more memory and cache, but
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* allow to read codes with fewer reads.
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* @param[in] nb_codes The number of provided length and (if supplied) symbol
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* entries.
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* @param[in] lens The lengths of the codes. Entries > 0 correspond to
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* valid codes; entries == 0 will be skipped and entries
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* with len < 0 indicate that the tree is incomplete and
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* has an open end of length -len at this position.
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* @param[in] lens_wrap Stride (in bytes) of the lengths.
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* @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
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* when the corresponding code is encountered.
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* May be NULL, then 0, 1, 2, 3, 4,... will be used.
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* @param[in] symbols_wrap Stride (in bytes) of the symbols.
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* @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
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* @param[in] offset An offset to apply to all the valid symbols.
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* @param[in] flags A combination of the VLC_INIT_* flags; notice that
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* VLC_INIT_INPUT_LE is pointless and ignored.
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*/
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int ff_vlc_init_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
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const int8_t *lens, int lens_wrap,
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const void *symbols, int symbols_wrap, int symbols_size,
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int offset, int flags, void *logctx);
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/**
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* Build VLC decoding tables suitable for use with get_vlc_multi()
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*
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* This function takes lengths and symbols and calculates the codes from them.
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* For this the input lengths and symbols have to be sorted according to "left
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* nodes in the corresponding tree first".
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*
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* @param[in,out] vlc The VLC to be initialized; table and table_allocated
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* must have been set when initializing a static VLC,
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* otherwise this will be treated as uninitialized.
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* @param[in,out] multi The VLC_MULTI to be initialized; table and table_allocated
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* must have been set when initializing a static VLC,
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* otherwise this will be treated as uninitialized.
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* @param[in] nb_bits The number of bits to use for the VLC table;
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* higher values take up more memory and cache, but
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* allow to read codes with fewer reads.
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* @param[in] nb_elems The max possible number of elements.
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* @param[in] nb_codes The number of provided length and (if supplied) symbol
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* entries.
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* @param[in] lens The lengths of the codes. Entries > 0 correspond to
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* valid codes; entries == 0 will be skipped and entries
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* with len < 0 indicate that the tree is incomplete and
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* has an open end of length -len at this position.
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* @param[in] lens_wrap Stride (in bytes) of the lengths.
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* @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
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* when the corresponding code is encountered.
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* May be NULL, then 0, 1, 2, 3, 4,... will be used.
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* @param[in] symbols_wrap Stride (in bytes) of the symbols.
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* @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
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* @param[in] offset An offset to apply to all the valid symbols.
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* @param[in] flags A combination of the VLC_INIT_* flags; notice that
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* VLC_INIT_INPUT_LE is pointless and ignored.
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*/
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int ff_vlc_init_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
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int nb_codes, const int8_t *lens, int lens_wrap,
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const void *symbols, int symbols_wrap, int symbols_size,
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int offset, int flags, void *logctx);
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void ff_vlc_free_multi(VLC_MULTI *vlc);
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void ff_vlc_free(VLC *vlc);
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#define VLC_INIT_USE_STATIC 1
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#define VLC_INIT_STATIC_OVERLONG (2 | VLC_INIT_USE_STATIC)
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/* If VLC_INIT_INPUT_LE is set, the LSB bit of the codes used to
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* initialize the VLC table is the first bit to be read. */
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#define VLC_INIT_INPUT_LE 4
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/* If set the VLC is intended for a little endian bitstream reader. */
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#define VLC_INIT_OUTPUT_LE 8
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#define VLC_INIT_LE (VLC_INIT_INPUT_LE | VLC_INIT_OUTPUT_LE)
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#define VLC_INIT_CUSTOM_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
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h, i, j, flags, static_size) \
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do { \
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static VLCElem table[static_size]; \
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(vlc)->table = table; \
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(vlc)->table_allocated = static_size; \
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ff_vlc_init_sparse(vlc, bits, a, b, c, d, e, f, g, h, i, j, \
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flags | VLC_INIT_USE_STATIC); \
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} while (0)
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#define VLC_INIT_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
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VLC_INIT_CUSTOM_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
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h, i, j, 0, static_size)
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#define VLC_INIT_LE_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
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VLC_INIT_CUSTOM_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
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h, i, j, VLC_INIT_LE, static_size)
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#define VLC_INIT_CUSTOM_STATIC(vlc, bits, a, b, c, d, e, f, g, flags, static_size) \
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VLC_INIT_CUSTOM_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
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NULL, 0, 0, flags, static_size)
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#define VLC_INIT_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
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VLC_INIT_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
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#define VLC_INIT_LE_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
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VLC_INIT_LE_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
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#define VLC_INIT_STATIC_FROM_LENGTHS(vlc, bits, nb_codes, lens, len_wrap, \
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symbols, symbols_wrap, symbols_size, \
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offset, flags, static_size) \
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do { \
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static VLCElem table[static_size]; \
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(vlc)->table = table; \
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(vlc)->table_allocated = static_size; \
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ff_vlc_init_from_lengths(vlc, bits, nb_codes, lens, len_wrap, \
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symbols, symbols_wrap, symbols_size, \
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offset, flags | VLC_INIT_USE_STATIC, \
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NULL); \
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} while (0)
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/**
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* For static VLCs, the number of bits can often be hardcoded
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* at each get_vlc2() callsite. Then using a full VLC would be uneconomical,
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* because only VLC.table would ever be accessed after initialization.
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* The following functions provide wrappers around the relevant ff_vlc_init_*
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* functions suitable for said task.
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*
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* The ff_vlc_init_tables_* functions are intended to be used for initializing
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* a series of VLCs. The user initializes a VLCInitState with the details
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* about the underlying array of VLCElem; it is automatically updated by
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* the ff_vlc_init_tables_* functions (i.e. table is incremented and size
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* decremented by the number of elements of the current table).
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* The VLC_INIT_STATIC_OVERLONG flag is also automatically added.
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* These functions return a pointer to the table just initialized,
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* potentially to be used in arrays of pointer to VLC tables.
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*
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* The ff_vlc_init_table_* functions are intended to be used for initializing
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* a single VLC table, given by table and table_size. The VLC_INIT_USE_STATIC
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* flag is automatically added.
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*/
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typedef struct VLCInitState {
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VLCElem *table; ///< points to where the next VLC table will be placed
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unsigned size; ///< remaining number of elements in table
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} VLCInitState;
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#define VLC_INIT_STATE(_table) { .table = (_table), .size = FF_ARRAY_ELEMS(_table) }
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void ff_vlc_init_table_from_lengths(VLCElem table[], int table_size,
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int nb_bits, int nb_codes,
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const int8_t *lens, int lens_wrap,
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const void *symbols, int symbols_wrap, int symbols_size,
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int offset, int flags);
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const VLCElem *ff_vlc_init_tables_from_lengths(VLCInitState *state,
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int nb_bits, int nb_codes,
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const int8_t *lens, int lens_wrap,
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const void *symbols, int symbols_wrap, int symbols_size,
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int offset, int flags);
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void ff_vlc_init_table_sparse(VLCElem table[], int table_size,
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int nb_bits, int nb_codes,
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const void *bits, int bits_wrap, int bits_size,
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const void *codes, int codes_wrap, int codes_size,
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const void *symbols, int symbols_wrap, int symbols_size,
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int flags);
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const VLCElem *ff_vlc_init_tables_sparse(VLCInitState *state,
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int nb_bits, int nb_codes,
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const void *bits, int bits_wrap, int bits_size,
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const void *codes, int codes_wrap, int codes_size,
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const void *symbols, int symbols_wrap, int symbols_size,
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int flags);
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static inline
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const VLCElem *ff_vlc_init_tables(VLCInitState *state,
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int nb_bits, int nb_codes,
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const void *bits, int bits_wrap, int bits_size,
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const void *codes, int codes_wrap, int codes_size,
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int flags)
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{
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return ff_vlc_init_tables_sparse(state, nb_bits, nb_codes,
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bits, bits_wrap, bits_size,
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codes, codes_wrap, codes_size,
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NULL, 0, 0, flags);
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}
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#define VLC_INIT_STATIC_SPARSE_TABLE(vlc_table, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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symbols, symbols_wrap, symbols_size, \
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flags) \
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ff_vlc_init_table_sparse(vlc_table, FF_ARRAY_ELEMS(vlc_table), \
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(nb_bits), (nb_codes), \
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(bits), (bits_wrap), (bits_size), \
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(codes), (codes_wrap), (codes_size), \
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(symbols), (symbols_wrap), (symbols_size), \
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(flags))
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#define VLC_INIT_STATIC_TABLE(vlc_table, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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flags) \
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ff_vlc_init_table_sparse(vlc_table, FF_ARRAY_ELEMS(vlc_table), \
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(nb_bits), (nb_codes), \
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(bits), (bits_wrap), (bits_size), \
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(codes), (codes_wrap), (codes_size), \
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NULL, 0, 0, (flags))
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#define VLC_INIT_STATIC_TABLE_FROM_LENGTHS(vlc_table, nb_bits, nb_codes, \
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lens, lens_wrap, \
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syms, syms_wrap, syms_size, \
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offset, flags) \
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ff_vlc_init_table_from_lengths(vlc_table, FF_ARRAY_ELEMS(vlc_table), \
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(nb_bits), (nb_codes), \
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(lens), (lens_wrap), \
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(syms), (syms_wrap), (syms_size), \
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(offset), (flags))
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#endif /* AVCODEC_VLC_H */
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