diff options
Diffstat (limited to 'chromium/third_party/dav1d/libdav1d/src/getbits.c')
| -rw-r--r-- | chromium/third_party/dav1d/libdav1d/src/getbits.c | 82 |
1 files changed, 49 insertions, 33 deletions
diff --git a/chromium/third_party/dav1d/libdav1d/src/getbits.c b/chromium/third_party/dav1d/libdav1d/src/getbits.c index 7bb20140e41..673070be3dd 100644 --- a/chromium/third_party/dav1d/libdav1d/src/getbits.c +++ b/chromium/third_party/dav1d/libdav1d/src/getbits.c @@ -36,51 +36,62 @@ void dav1d_init_get_bits(GetBits *const c, const uint8_t *const data, const size_t sz) { - // If sz were 0, c->eof would need to be initialized to 1. assert(sz); c->ptr = c->ptr_start = data; c->ptr_end = &c->ptr_start[sz]; - c->bits_left = 0; c->state = 0; + c->bits_left = 0; c->error = 0; - c->eof = 0; } -static void refill(GetBits *const c, const unsigned n) { - assert(c->bits_left <= 56); - uint64_t state = 0; - do { - state <<= 8; - c->bits_left += 8; - if (!c->eof) - state |= *c->ptr++; +unsigned dav1d_get_bit(GetBits *const c) { + if (!c->bits_left) { if (c->ptr >= c->ptr_end) { - c->error = c->eof; - c->eof = 1; + c->error = 1; + } else { + const unsigned state = *c->ptr++; + c->bits_left = 7; + c->state = (uint64_t) state << 57; + return state >> 7; } - } while (n > c->bits_left); - c->state |= state << (64 - c->bits_left); -} - -unsigned dav1d_get_bits(GetBits *const c, const unsigned n) { - assert(n <= 32 /* can go up to 57 if we change return type */); - assert(n /* can't shift state by 64 */); - - if (n > c->bits_left) refill(c, n); + } const uint64_t state = c->state; - c->bits_left -= n; - c->state <<= n; + c->bits_left--; + c->state = state << 1; + return (unsigned) (state >> 63); +} - return (unsigned) (state >> (64 - n)); +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); } -int dav1d_get_sbits(GetBits *const c, const unsigned n) { - const int shift = 31 - n; - const int res = dav1d_get_bits(c, n + 1) << shift; - return res >> shift; +#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; @@ -108,15 +119,20 @@ unsigned dav1d_get_uniform(GetBits *const c, const unsigned max) { 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_bits(c, 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; - while (!dav1d_get_bits(c, 1)) + do { if (++n_bits == 32) return 0xFFFFFFFFU; - return n_bits ? ((1U << n_bits) - 1) + dav1d_get_bits(c, n_bits) : 0; + } 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, @@ -132,7 +148,7 @@ static unsigned get_bits_subexp_u(GetBits *const c, const unsigned ref, break; } - if (!dav1d_get_bits(c, 1)) { + if (!dav1d_get_bit(c)) { v += dav1d_get_bits(c, b); break; } |