| // 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 |
| |
| #ifdef WEBP_FORCE_ALIGNED |
| #include <string.h> // memcpy |
| #endif |
| |
| #include "./bit_reader.h" |
| #include "./endian_inl.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 range_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_INLINE void VP8LoadNewBytes(VP8BitReader* const br) { |
| assert(br != NULL && br->buf_ != NULL); |
| // Read 'BITS' bits at a time if possible. |
| if (br->buf_ + sizeof(lbit_t) <= br->buf_end_) { |
| // convert memory type to register type (with some zero'ing!) |
| bit_t bits; |
| #if defined(WEBP_FORCE_ALIGNED) |
| lbit_t in_bits; |
| memcpy(&in_bits, br->buf_, sizeof(in_bits)); |
| #elif defined(__mips__) && !defined(__mips64) // MIPS |
| // 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 |
| const lbit_t in_bits = *(const lbit_t*)br->buf_; |
| #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); |
| #if defined(__arm__) || defined(_M_ARM) // ARM-specific |
| const int bit = ((int)(split - value) >> 31) & 1; |
| if (value > split) { |
| range -= split + 1; |
| br->value_ -= (bit_t)(split + 1) << pos; |
| } else { |
| range = split; |
| } |
| #else // faster version on x86 |
| 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; |
| } |
| #endif |
| if (range <= (range_t)0x7e) { |
| const int shift = kVP8Log2Range[range]; |
| range = kVP8NewRange[range]; |
| br->bits_ -= shift; |
| } |
| br->range_ = range; |
| return bit; |
| } |
| } |
| |
| // simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here) |
| static 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; |
| } |
| } |
| |
| #ifdef __cplusplus |
| } // extern "C" |
| #endif |
| |
| #endif // WEBP_UTILS_BIT_READER_INL_H_ |