// 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* 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_UTILS_H_