// 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_UTILS_H_ #define WEBP_UTILS_BIT_READER_INL_UTILS_H_ #ifdef HAVE_CONFIG_H #include "src/webp/config.h" #endif #include <string.h> // for memcpy #include "src/dsp/dsp.h" #include "src/utils/bit_reader_utils.h" #include "src/utils/endian_inl_utils.h" #include "src/utils/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* WEBP_RESTRICT 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* WEBP_RESTRICT const br, int prob, const char label[]) { // 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; BT_TRACK(br); 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* WEBP_RESTRICT const br, int v, const char label[]) { 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; BT_TRACK(br); return (v ^ mask) - mask; } } static WEBP_INLINE int VP8GetBitAlt(VP8BitReader* WEBP_RESTRICT const br, int prob, const char label[]) { // 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; BT_TRACK(br); return bit; } } #ifdef __cplusplus } // extern "C" #endif #endif // WEBP_UTILS_BIT_READER_INL_UTILS_H_