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Diffstat (limited to 'drivers/webpold/utils/bit_reader.h')
| -rw-r--r-- | drivers/webpold/utils/bit_reader.h | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/drivers/webpold/utils/bit_reader.h b/drivers/webpold/utils/bit_reader.h new file mode 100644 index 0000000000..43cd948fd4 --- /dev/null +++ b/drivers/webpold/utils/bit_reader.h @@ -0,0 +1,198 @@ +// +// Copyright 2010 Google Inc. All Rights Reserved. +// +// This code is licensed under the same terms as WebM: +// Software License Agreement: http://www.webmproject.org/license/software/ +// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ +// ----------------------------------------------------------------------------- +// +// Boolean decoder +// +// Author: Skal (pascal.massimino@gmail.com) +// Vikas Arora (vikaas.arora@gmail.com) + +#ifndef WEBP_UTILS_BIT_READER_H_ +#define WEBP_UTILS_BIT_READER_H_ + +#include <assert.h> +#ifdef _MSC_VER +#include <stdlib.h> // _byteswap_ulong +#endif +#include <string.h> // For memcpy +#include "../types.h" + +#if defined(__cplusplus) || defined(c_plusplus) +extern "C" { +#endif + +#define BITS 32 // can be 32, 16 or 8 +#define MASK ((((bit_t)1) << (BITS)) - 1) +#if (BITS == 32) +typedef uint64_t bit_t; // natural register type +typedef uint32_t lbit_t; // natural type for memory I/O +#elif (BITS == 16) +typedef uint32_t bit_t; +typedef uint16_t lbit_t; +#else +typedef uint32_t bit_t; +typedef uint8_t lbit_t; +#endif + +//------------------------------------------------------------------------------ +// Bitreader and code-tree reader + +typedef struct VP8BitReader VP8BitReader; +struct VP8BitReader { + const uint8_t* buf_; // next byte to be read + const uint8_t* buf_end_; // end of read buffer + int eof_; // true if input is exhausted + + // boolean decoder + bit_t range_; // current range minus 1. In [127, 254] interval. + bit_t value_; // current value + int missing_; // number of missing bits in value_ (8bit) +}; + +// Initialize the bit reader and the boolean decoder. +void VP8InitBitReader(VP8BitReader* const br, + const uint8_t* const start, const uint8_t* const end); + +// return the next value made of 'num_bits' bits +uint32_t VP8GetValue(VP8BitReader* const br, int num_bits); +static WEBP_INLINE uint32_t VP8Get(VP8BitReader* const br) { + return VP8GetValue(br, 1); +} + +// return the next value with sign-extension. +int32_t VP8GetSignedValue(VP8BitReader* const br, int num_bits); + +// Read a bit with proba 'prob'. Speed-critical function! +extern const uint8_t kVP8Log2Range[128]; +extern const bit_t kVP8NewRange[128]; + +void VP8LoadFinalBytes(VP8BitReader* const br); // special case for the tail + +static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) { + assert(br && br->buf_); + // 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; + lbit_t in_bits = *(lbit_t*)br->buf_; + br->buf_ += (BITS) >> 3; +#if !defined(__BIG_ENDIAN__) +#if (BITS == 32) +#if defined(__i386__) || defined(__x86_64__) + __asm__ volatile("bswap %k0" : "=r"(in_bits) : "0"(in_bits)); + bits = (bit_t)in_bits; // 32b -> 64b zero-extension +#elif defined(_MSC_VER) + bits = _byteswap_ulong(in_bits); +#else + bits = (bit_t)(in_bits >> 24) | ((in_bits >> 8) & 0xff00) + | ((in_bits << 8) & 0xff0000) | (in_bits << 24); +#endif // x86 +#elif (BITS == 16) + // gcc will recognize a 'rorw $8, ...' here: + bits = (bit_t)(in_bits >> 8) | ((in_bits & 0xff) << 8); +#endif +#else // LITTLE_ENDIAN + bits = (bit_t)in_bits; +#endif + br->value_ |= bits << br->missing_; + br->missing_ -= (BITS); + } else { + VP8LoadFinalBytes(br); // no need to be inlined + } +} + +static WEBP_INLINE int VP8BitUpdate(VP8BitReader* const br, bit_t split) { + const bit_t value_split = split | (MASK); + if (br->missing_ > 0) { // Make sure we have a least BITS bits in 'value_' + VP8LoadNewBytes(br); + } + if (br->value_ > value_split) { + br->range_ -= value_split + 1; + br->value_ -= value_split + 1; + return 1; + } else { + br->range_ = value_split; + return 0; + } +} + +static WEBP_INLINE void VP8Shift(VP8BitReader* const br) { + // range_ is in [0..127] interval here. + const int idx = br->range_ >> (BITS); + const int shift = kVP8Log2Range[idx]; + br->range_ = kVP8NewRange[idx]; + br->value_ <<= shift; + br->missing_ += shift; +} + +static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) { + // It's important to avoid generating a 64bit x 64bit multiply here. + // We just need an 8b x 8b after all. + const bit_t split = + (bit_t)((uint32_t)(br->range_ >> (BITS)) * prob) << ((BITS) - 8); + const int bit = VP8BitUpdate(br, split); + if (br->range_ <= (((bit_t)0x7e << (BITS)) | (MASK))) { + VP8Shift(br); + } + return bit; +} + +static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) { + const bit_t split = (br->range_ >> 1); + const int bit = VP8BitUpdate(br, split); + VP8Shift(br); + return bit ? -v : v; +} + + +// ----------------------------------------------------------------------------- +// Bitreader + +typedef struct { + uint64_t val_; + const uint8_t* buf_; + size_t len_; + size_t pos_; + int bit_pos_; + int eos_; + int error_; +} VP8LBitReader; + +void VP8LInitBitReader(VP8LBitReader* const br, + const uint8_t* const start, + size_t length); + +// Sets a new data buffer. +void VP8LBitReaderSetBuffer(VP8LBitReader* const br, + const uint8_t* const buffer, size_t length); + +// Reads the specified number of bits from Read Buffer. +// Flags an error in case end_of_stream or n_bits is more than allowed limit. +// Flags eos if this read attempt is going to cross the read buffer. +uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits); + +// Reads one bit from Read Buffer. Flags an error in case end_of_stream. +// Flags eos after reading last bit from the buffer. +uint32_t VP8LReadOneBit(VP8LBitReader* const br); + +// VP8LReadOneBitUnsafe is faster than VP8LReadOneBit, but it can be called only +// 32 times after the last VP8LFillBitWindow. Any subsequent calls +// (without VP8LFillBitWindow) will return invalid data. +static WEBP_INLINE uint32_t VP8LReadOneBitUnsafe(VP8LBitReader* const br) { + const uint32_t val = (br->val_ >> br->bit_pos_) & 1; + ++br->bit_pos_; + return val; +} + +// Advances the Read buffer by 4 bytes to make room for reading next 32 bits. +void VP8LFillBitWindow(VP8LBitReader* const br); + +#if defined(__cplusplus) || defined(c_plusplus) +} // extern "C" +#endif + +#endif /* WEBP_UTILS_BIT_READER_H_ */ |