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Diffstat (limited to 'third_party/dav1d/src/getbits.c')
| -rw-r--r-- | third_party/dav1d/src/getbits.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/third_party/dav1d/src/getbits.c b/third_party/dav1d/src/getbits.c new file mode 100644 index 0000000000..673070be3d --- /dev/null +++ b/third_party/dav1d/src/getbits.c @@ -0,0 +1,178 @@ +/* + * Copyright © 2018, VideoLAN and dav1d authors + * Copyright © 2018, Two Orioles, LLC + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR + * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "config.h" + +#include <limits.h> + +#include "common/intops.h" + +#include "src/getbits.h" + +void dav1d_init_get_bits(GetBits *const c, const uint8_t *const data, + const size_t sz) +{ + assert(sz); + c->ptr = c->ptr_start = data; + c->ptr_end = &c->ptr_start[sz]; + c->state = 0; + c->bits_left = 0; + c->error = 0; +} + +unsigned dav1d_get_bit(GetBits *const c) { + if (!c->bits_left) { + if (c->ptr >= c->ptr_end) { + c->error = 1; + } else { + const unsigned state = *c->ptr++; + c->bits_left = 7; + c->state = (uint64_t) state << 57; + return state >> 7; + } + } + + const uint64_t state = c->state; + c->bits_left--; + c->state = state << 1; + return (unsigned) (state >> 63); +} + +static inline void refill(GetBits *const c, const int n) { + assert(c->bits_left >= 0 && c->bits_left < 32); + unsigned state = 0; + do { + if (c->ptr >= c->ptr_end) { + c->error = 1; + if (state) break; + return; + } + state = (state << 8) | *c->ptr++; + c->bits_left += 8; + } while (n > c->bits_left); + c->state |= (uint64_t) state << (64 - c->bits_left); +} + +#define GET_BITS(name, type, type64) \ +type name(GetBits *const c, const int n) { \ + assert(n > 0 && n <= 32); \ + /* Unsigned cast avoids refill after eob */ \ + if ((unsigned) n > (unsigned) c->bits_left) \ + refill(c, n); \ + const uint64_t state = c->state; \ + c->bits_left -= n; \ + c->state = state << n; \ + return (type) ((type64) state >> (64 - n)); \ +} + +GET_BITS(dav1d_get_bits, unsigned, uint64_t) +GET_BITS(dav1d_get_sbits, int, int64_t) + +unsigned dav1d_get_uleb128(GetBits *const c) { + uint64_t val = 0; + unsigned i = 0, more; + + do { + const int v = dav1d_get_bits(c, 8); + more = v & 0x80; + val |= ((uint64_t) (v & 0x7F)) << i; + i += 7; + } while (more && i < 56); + + if (val > UINT_MAX || more) { + c->error = 1; + return 0; + } + + return (unsigned) val; +} + +unsigned dav1d_get_uniform(GetBits *const c, const unsigned max) { + // Output in range [0..max-1] + // max must be > 1, or else nothing is read from the bitstream + assert(max > 1); + const int l = ulog2(max) + 1; + assert(l > 1); + const unsigned m = (1U << l) - max; + const unsigned v = dav1d_get_bits(c, l - 1); + return v < m ? v : (v << 1) - m + dav1d_get_bit(c); +} + +unsigned dav1d_get_vlc(GetBits *const c) { + if (dav1d_get_bit(c)) + return 0; + + int n_bits = 0; + do { + if (++n_bits == 32) + return 0xFFFFFFFFU; + } while (!dav1d_get_bit(c)); + + return ((1U << n_bits) - 1) + dav1d_get_bits(c, n_bits); +} + +static unsigned get_bits_subexp_u(GetBits *const c, const unsigned ref, + const unsigned n) +{ + unsigned v = 0; + + for (int i = 0;; i++) { + const int b = i ? 3 + i - 1 : 3; + + if (n < v + 3 * (1 << b)) { + v += dav1d_get_uniform(c, n - v + 1); + break; + } + + if (!dav1d_get_bit(c)) { + v += dav1d_get_bits(c, b); + break; + } + + v += 1 << b; + } + + return ref * 2 <= n ? inv_recenter(ref, v) : n - inv_recenter(n - ref, v); +} + +int dav1d_get_bits_subexp(GetBits *const c, const int ref, const unsigned n) { + return (int) get_bits_subexp_u(c, ref + (1 << n), 2 << n) - (1 << n); +} + +void dav1d_bytealign_get_bits(GetBits *c) { + // bits_left is never more than 7, because it is only incremented + // by refill(), called by dav1d_get_bits and that never reads more + // than 7 bits more than it needs. + // + // If this wasn't true, we would need to work out how many bits to + // discard (bits_left % 8), subtract that from bits_left and then + // shift state right by that amount. + assert(c->bits_left <= 7); + + c->bits_left = 0; + c->state = 0; +} |