diff options
Diffstat (limited to 'third_party/libwebp/utils/bit_reader.c')
| -rw-r--r-- | third_party/libwebp/utils/bit_reader.c | 107 |
1 files changed, 45 insertions, 62 deletions
diff --git a/third_party/libwebp/utils/bit_reader.c b/third_party/libwebp/utils/bit_reader.c index 1afb1db..d6cfd86 100644 --- a/third_party/libwebp/utils/bit_reader.c +++ b/third_party/libwebp/utils/bit_reader.c @@ -15,7 +15,11 @@ extern "C" { #endif -#define MK(X) (((bit_t)(X) << (BITS)) | (MASK)) +#ifndef USE_RIGHT_JUSTIFY +#define MK(X) (((range_t)(X) << (BITS)) | (MASK)) +#else +#define MK(X) ((range_t)(X)) +#endif //------------------------------------------------------------------------------ // VP8BitReader @@ -29,7 +33,7 @@ void VP8InitBitReader(VP8BitReader* const br, br->buf_ = start; br->buf_end_ = end; br->value_ = 0; - br->missing_ = 8; // to load the very first 8bits + br->bits_ = -8; // to load the very first 8bits br->eof_ = 0; } @@ -46,7 +50,7 @@ const uint8_t kVP8Log2Range[128] = { }; // range = (range << kVP8Log2Range[range]) + trailing 1's -const bit_t kVP8NewRange[128] = { +const range_t kVP8NewRange[128] = { MK(127), MK(127), MK(191), MK(127), MK(159), MK(191), MK(223), MK(127), MK(143), MK(159), MK(175), MK(191), MK(207), MK(223), MK(239), MK(127), MK(135), MK(143), MK(151), MK(159), MK(167), MK(175), MK(183), MK(191), @@ -71,9 +75,19 @@ void VP8LoadFinalBytes(VP8BitReader* const br) { assert(br != NULL && br->buf_ != NULL); // Only read 8bits at a time if (br->buf_ < br->buf_end_) { - br->value_ |= (bit_t)(*br->buf_++) << ((BITS) - 8 + br->missing_); - br->missing_ -= 8; - } else { +#ifndef USE_RIGHT_JUSTIFY + br->value_ |= (bit_t)(*br->buf_++) << ((BITS) - 8 - br->bits_); +#else + br->value_ = (bit_t)(*br->buf_++) | (br->value_ << 8); +#endif + br->bits_ += 8; + } else if (!br->eof_) { +#ifdef USE_RIGHT_JUSTIFY + // These are not strictly needed, but it makes the behaviour + // consistent for both USE_RIGHT_JUSTIFY and !USE_RIGHT_JUSTIFY. + br->value_ <<= 8; + br->bits_ += 8; +#endif br->eof_ = 1; } } @@ -99,6 +113,10 @@ int32_t VP8GetSignedValue(VP8BitReader* const br, int bits) { #define MAX_NUM_BIT_READ 25 +#define LBITS 64 // Number of bits prefetched. +#define WBITS 32 // Minimum number of bytes needed after VP8LFillBitWindow. +#define LOG8_WBITS 4 // Number of bytes needed to store WBITS bits. + static const uint32_t kBitMask[MAX_NUM_BIT_READ] = { 0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215 @@ -120,7 +138,7 @@ void VP8LInitBitReader(VP8LBitReader* const br, br->eos_ = 0; br->error_ = 0; for (i = 0; i < sizeof(br->val_) && i < br->len_; ++i) { - br->val_ |= ((uint64_t)br->buf_[br->pos_]) << (8 * i); + br->val_ |= ((vp8l_val_t)br->buf_[br->pos_]) << (8 * i); ++br->pos_; } } @@ -135,91 +153,56 @@ void VP8LBitReaderSetBuffer(VP8LBitReader* const br, br->len_ = len; } +// If not at EOS, reload up to LBITS byte-by-byte static void ShiftBytes(VP8LBitReader* const br) { while (br->bit_pos_ >= 8 && br->pos_ < br->len_) { br->val_ >>= 8; - br->val_ |= ((uint64_t)br->buf_[br->pos_]) << 56; + br->val_ |= ((vp8l_val_t)br->buf_[br->pos_]) << (LBITS - 8); ++br->pos_; br->bit_pos_ -= 8; } } void VP8LFillBitWindow(VP8LBitReader* const br) { - if (br->bit_pos_ >= 32) { -#if defined(__x86_64__) || defined(_M_X64) - if (br->pos_ + 8 < br->len_) { - br->val_ >>= 32; + if (br->bit_pos_ >= WBITS) { +#if (defined(__x86_64__) || defined(_M_X64)) + if (br->pos_ + sizeof(br->val_) < br->len_) { + br->val_ >>= WBITS; + br->bit_pos_ -= WBITS; // The expression below needs a little-endian arch to work correctly. // This gives a large speedup for decoding speed. - br->val_ |= *(const uint64_t *)(br->buf_ + br->pos_) << 32; - br->pos_ += 4; - br->bit_pos_ -= 32; - } else { - // Slow path. - ShiftBytes(br); + br->val_ |= *(const vp8l_val_t*)(br->buf_ + br->pos_) << (LBITS - WBITS); + br->pos_ += LOG8_WBITS; + return; } -#else - // Always the slow path. - ShiftBytes(br); #endif - } - if (br->pos_ == br->len_ && br->bit_pos_ == 64) { - br->eos_ = 1; - } -} - -uint32_t VP8LReadOneBit(VP8LBitReader* const br) { - const uint32_t val = (br->val_ >> br->bit_pos_) & 1; - // Flag an error at end_of_stream. - if (!br->eos_) { - ++br->bit_pos_; - if (br->bit_pos_ >= 32) { - ShiftBytes(br); - } - // After this last bit is read, check if eos needs to be flagged. - if (br->pos_ == br->len_ && br->bit_pos_ == 64) { + ShiftBytes(br); // Slow path. + if (br->pos_ == br->len_ && br->bit_pos_ == LBITS) { br->eos_ = 1; } - } else { - br->error_ = 1; } - return val; } uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits) { - uint32_t val = 0; assert(n_bits >= 0); // Flag an error if end_of_stream or n_bits is more than allowed limit. if (!br->eos_ && n_bits < MAX_NUM_BIT_READ) { + const uint32_t val = + (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits]; + const int new_bits = br->bit_pos_ + n_bits; + br->bit_pos_ = new_bits; // If this read is going to cross the read buffer, set the eos flag. if (br->pos_ == br->len_) { - if ((br->bit_pos_ + n_bits) >= 64) { + if (new_bits >= LBITS) { br->eos_ = 1; - if ((br->bit_pos_ + n_bits) > 64) return val; - } - } - val = (br->val_ >> br->bit_pos_) & kBitMask[n_bits]; - br->bit_pos_ += n_bits; - if (br->bit_pos_ >= 40) { - if (br->pos_ + 5 < br->len_) { - br->val_ >>= 40; - br->val_ |= - (((uint64_t)br->buf_[br->pos_ + 0]) << 24) | - (((uint64_t)br->buf_[br->pos_ + 1]) << 32) | - (((uint64_t)br->buf_[br->pos_ + 2]) << 40) | - (((uint64_t)br->buf_[br->pos_ + 3]) << 48) | - (((uint64_t)br->buf_[br->pos_ + 4]) << 56); - br->pos_ += 5; - br->bit_pos_ -= 40; - } - if (br->bit_pos_ >= 8) { - ShiftBytes(br); } } + ShiftBytes(br); + return val; } else { br->error_ = 1; + return 0; } - return val; } //------------------------------------------------------------------------------ |