2d764069be
In C, qualifiers for arrays are broken: const VLC_TYPE (*foo)[2] is a pointer to an array of two const VLC_TYPE elements and unfortunately this is not compatible with a pointer to a const array of two VLC_TYPE, because the latter does not exist as array types are never qualified (the qualifier applies to the base type instead). This is the reason why get_vlc2() doesn't accept a const VLC table despite not modifying the table at all, as there is no automatic conversion from VLC_TYPE (*)[2] to const VLC_TYPE (*)[2]. Fix this by using a structure VLCElem for the VLC table. This also has the advantage of making it clear which element is which. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
145 lines
6.9 KiB
C
145 lines
6.9 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 <stdint.h>
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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 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 init_vlc(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_init_vlc_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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int ff_init_vlc_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 INIT_VLC_* flags; notice that
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* INIT_VLC_INPUT_LE is pointless and ignored.
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*/
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int ff_init_vlc_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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void ff_free_vlc(VLC *vlc);
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/* If INIT_VLC_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 INIT_VLC_INPUT_LE 2
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/* If set the VLC is intended for a little endian bitstream reader. */
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#define INIT_VLC_OUTPUT_LE 8
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#define INIT_VLC_LE (INIT_VLC_INPUT_LE | INIT_VLC_OUTPUT_LE)
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#define INIT_VLC_USE_NEW_STATIC 4
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#define INIT_VLC_STATIC_OVERLONG (1 | INIT_VLC_USE_NEW_STATIC)
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#define INIT_CUSTOM_VLC_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_init_vlc_sparse(vlc, bits, a, b, c, d, e, f, g, h, i, j, \
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flags | INIT_VLC_USE_NEW_STATIC); \
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} while (0)
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#define INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
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INIT_CUSTOM_VLC_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 INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
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INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
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h, i, j, INIT_VLC_LE, static_size)
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#define INIT_CUSTOM_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, flags, static_size) \
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INIT_CUSTOM_VLC_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 INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
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INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
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#define INIT_LE_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
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INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
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#define INIT_VLC_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_init_vlc_from_lengths(vlc, bits, nb_codes, lens, len_wrap, \
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symbols, symbols_wrap, symbols_size, \
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offset, flags | INIT_VLC_USE_NEW_STATIC, \
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NULL); \
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} while (0)
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#endif /* AVCODEC_VLC_H */
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