71 lines
2.8 KiB
C
71 lines
2.8 KiB
C
/*
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* Copyright © 2018, VideoLAN and dav1d authors
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* Copyright © 2018, Two Orioles, LLC
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef DAV1D_SRC_GETBITS_H
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#define DAV1D_SRC_GETBITS_H
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#include <stddef.h>
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#include <stdint.h>
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typedef struct GetBits {
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uint64_t state;
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int bits_left, error;
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const uint8_t *ptr, *ptr_start, *ptr_end;
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} GetBits;
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void dav1d_init_get_bits(GetBits *c, const uint8_t *data, size_t sz);
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unsigned dav1d_get_bit(GetBits *c);
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unsigned dav1d_get_bits(GetBits *c, int n);
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int dav1d_get_sbits(GetBits *c, int n);
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unsigned dav1d_get_uleb128(GetBits *c);
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// Output in range 0..max-1
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unsigned dav1d_get_uniform(GetBits *c, unsigned max);
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unsigned dav1d_get_vlc(GetBits *c);
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int dav1d_get_bits_subexp(GetBits *c, int ref, unsigned n);
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// Discard bits from the buffer until we're next byte-aligned.
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static inline void dav1d_bytealign_get_bits(GetBits *c) {
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// bits_left is never more than 7, because it is only incremented
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// by refill(), called by dav1d_get_bits and that never reads more
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// than 7 bits more than it needs.
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//
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// If this wasn't true, we would need to work out how many bits to
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// discard (bits_left % 8), subtract that from bits_left and then
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// shift state right by that amount.
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assert(c->bits_left <= 7);
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c->bits_left = 0;
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c->state = 0;
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}
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// Return the current bit position relative to the start of the buffer.
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static inline unsigned dav1d_get_bits_pos(const GetBits *c) {
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return (unsigned) (c->ptr - c->ptr_start) * 8 - c->bits_left;
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}
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#endif /* DAV1D_SRC_GETBITS_H */
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