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Diffstat (limited to 'media/libwebp/utils/bit_reader_inl_utils.h')
| -rw-r--r-- | media/libwebp/utils/bit_reader_inl_utils.h | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/media/libwebp/utils/bit_reader_inl_utils.h b/media/libwebp/utils/bit_reader_inl_utils.h new file mode 100644 index 000000000..fd7fb0446 --- /dev/null +++ b/media/libwebp/utils/bit_reader_inl_utils.h @@ -0,0 +1,190 @@ +// Copyright 2014 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Specific inlined methods for boolean decoder [VP8GetBit() ...] +// This file should be included by the .c sources that actually need to call +// these methods. +// +// Author: Skal (pascal.massimino@gmail.com) + +#ifndef WEBP_UTILS_BIT_READER_INL_H_ +#define WEBP_UTILS_BIT_READER_INL_H_ + +#ifdef HAVE_CONFIG_H +#include "../webp/config.h" +#endif + +#include <string.h> // for memcpy + +#include "../dsp/dsp.h" +#include "./bit_reader_utils.h" +#include "./endian_inl_utils.h" +#include "./utils.h" + +#ifdef __cplusplus +extern "C" { +#endif + +//------------------------------------------------------------------------------ +// Derived type lbit_t = natural type for memory I/O + +#if (BITS > 32) +typedef uint64_t lbit_t; +#elif (BITS > 16) +typedef uint32_t lbit_t; +#elif (BITS > 8) +typedef uint16_t lbit_t; +#else +typedef uint8_t lbit_t; +#endif + +extern const uint8_t kVP8Log2Range[128]; +extern const uint8_t kVP8NewRange[128]; + +// special case for the tail byte-reading +void VP8LoadFinalBytes(VP8BitReader* const br); + +//------------------------------------------------------------------------------ +// Inlined critical functions + +// makes sure br->value_ has at least BITS bits worth of data +static WEBP_UBSAN_IGNORE_UNDEF WEBP_INLINE +void VP8LoadNewBytes(VP8BitReader* const br) { + assert(br != NULL && br->buf_ != NULL); + // Read 'BITS' bits at a time if possible. + if (br->buf_ < br->buf_max_) { + // convert memory type to register type (with some zero'ing!) + bit_t bits; +#if defined(WEBP_USE_MIPS32) + // This is needed because of un-aligned read. + lbit_t in_bits; + lbit_t* p_buf_ = (lbit_t*)br->buf_; + __asm__ volatile( + ".set push \n\t" + ".set at \n\t" + ".set macro \n\t" + "ulw %[in_bits], 0(%[p_buf_]) \n\t" + ".set pop \n\t" + : [in_bits]"=r"(in_bits) + : [p_buf_]"r"(p_buf_) + : "memory", "at" + ); +#else + lbit_t in_bits; + memcpy(&in_bits, br->buf_, sizeof(in_bits)); +#endif + br->buf_ += BITS >> 3; +#if !defined(WORDS_BIGENDIAN) +#if (BITS > 32) + bits = BSwap64(in_bits); + bits >>= 64 - BITS; +#elif (BITS >= 24) + bits = BSwap32(in_bits); + bits >>= (32 - BITS); +#elif (BITS == 16) + bits = BSwap16(in_bits); +#else // BITS == 8 + bits = (bit_t)in_bits; +#endif // BITS > 32 +#else // WORDS_BIGENDIAN + bits = (bit_t)in_bits; + if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS); +#endif + br->value_ = bits | (br->value_ << BITS); + br->bits_ += BITS; + } else { + VP8LoadFinalBytes(br); // no need to be inlined + } +} + +// Read a bit with proba 'prob'. Speed-critical function! +static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) { + // Don't move this declaration! It makes a big speed difference to store + // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't + // alter br->range_ value. + range_t range = br->range_; + if (br->bits_ < 0) { + VP8LoadNewBytes(br); + } + { + const int pos = br->bits_; + const range_t split = (range * prob) >> 8; + const range_t value = (range_t)(br->value_ >> pos); + const int bit = (value > split); + if (bit) { + range -= split; + br->value_ -= (bit_t)(split + 1) << pos; + } else { + range = split + 1; + } + { + const int shift = 7 ^ BitsLog2Floor(range); + range <<= shift; + br->bits_ -= shift; + } + br->range_ = range - 1; + return bit; + } +} + +// simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here) +static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE +int VP8GetSigned(VP8BitReader* const br, int v) { + if (br->bits_ < 0) { + VP8LoadNewBytes(br); + } + { + const int pos = br->bits_; + const range_t split = br->range_ >> 1; + const range_t value = (range_t)(br->value_ >> pos); + const int32_t mask = (int32_t)(split - value) >> 31; // -1 or 0 + br->bits_ -= 1; + br->range_ += mask; + br->range_ |= 1; + br->value_ -= (bit_t)((split + 1) & mask) << pos; + return (v ^ mask) - mask; + } +} + +static WEBP_INLINE int VP8GetBitAlt(VP8BitReader* const br, int prob) { + // Don't move this declaration! It makes a big speed difference to store + // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't + // alter br->range_ value. + range_t range = br->range_; + if (br->bits_ < 0) { + VP8LoadNewBytes(br); + } + { + const int pos = br->bits_; + const range_t split = (range * prob) >> 8; + const range_t value = (range_t)(br->value_ >> pos); + int bit; // Don't use 'const int bit = (value > split);", it's slower. + if (value > split) { + range -= split + 1; + br->value_ -= (bit_t)(split + 1) << pos; + bit = 1; + } else { + range = split; + bit = 0; + } + if (range <= (range_t)0x7e) { + const int shift = kVP8Log2Range[range]; + range = kVP8NewRange[range]; + br->bits_ -= shift; + } + br->range_ = range; + return bit; + } +} + +#ifdef __cplusplus +} // extern "C" +#endif + +#endif // WEBP_UTILS_BIT_READER_INL_H_ |