// Copyright 2012 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.

// -----------------------------------------------------------------------------

//

// Image transforms and color space conversion methods for lossless decoder.

//

// Authors: Vikas Arora (vikaas.arora@gmail.com)

//          Jyrki Alakuijala (jyrki@google.com)

//          Vincent Rabaud (vrabaud@google.com)

#ifndef WEBP_DSP_LOSSLESS_COMMON_H_

#define WEBP_DSP_LOSSLESS_COMMON_H_

#include "src/webp/types.h"

#include "src/utils/utils.h"

#ifdef __cplusplus

extern "C" {

#endif

//------------------------------------------------------------------------------

// Decoding

// color mapping related functions.

static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) {

  return (idx >> 8) & 0xff;

}

static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) {

  return idx;

}

static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) {

  return val;

}

static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) {

  return (val >> 8) & 0xff;

}

//------------------------------------------------------------------------------

// Misc methods.

// Computes sampled size of 'size' when sampling using 'sampling bits'.

static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,

                                              uint32_t sampling_bits) {

  return (size + (1 << sampling_bits) - 1) >> sampling_bits;

}

// Converts near lossless quality into max number of bits shaved off.

static WEBP_INLINE int VP8LNearLosslessBits(int near_lossless_quality) {

  //    100 -> 0

  // 80..99 -> 1

  // 60..79 -> 2

  // 40..59 -> 3

  // 20..39 -> 4

  //  0..19 -> 5

  return 5 - near_lossless_quality / 20;

}

// -----------------------------------------------------------------------------

// Faster logarithm for integers. Small values use a look-up table.

// The threshold till approximate version of log_2 can be used.

// Practically, we can get rid of the call to log() as the two values match to

// very high degree (the ratio of these two is 0.99999x).

// Keeping a high threshold for now.

#define APPROX_LOG_WITH_CORRECTION_MAX  65536

#define APPROX_LOG_MAX                   4096

#define LOG_2_RECIPROCAL 1.44269504088896338700465094007086

#define LOG_LOOKUP_IDX_MAX 256

extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];

extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];

typedef float (*VP8LFastLog2SlowFunc)(uint32_t v);

extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;

extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow;

static WEBP_INLINE float VP8LFastLog2(uint32_t v) {

  return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);

}

// Fast calculation of v * log2(v) for integer input.

static WEBP_INLINE float VP8LFastSLog2(uint32_t v) {

  return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);

}

// -----------------------------------------------------------------------------

// PrefixEncode()

// Splitting of distance and length codes into prefixes and

// extra bits. The prefixes are encoded with an entropy code

// while the extra bits are stored just as normal bits.

static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,

                                                  int* const extra_bits) {

  const int highest_bit = BitsLog2Floor(--distance);

  const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;

  *extra_bits = highest_bit - 1;

  *code = 2 * highest_bit + second_highest_bit;

}

static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,

                                              int* const extra_bits,

                                              int* const extra_bits_value) {

  const int highest_bit = BitsLog2Floor(--distance);

  const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;

  *extra_bits = highest_bit - 1;

  *extra_bits_value = distance & ((1 << *extra_bits) - 1);

  *code = 2 * highest_bit + second_highest_bit;

}

#define PREFIX_LOOKUP_IDX_MAX   512

typedef struct {

  int8_t code_;

  int8_t extra_bits_;

} VP8LPrefixCode;

// These tables are derived using VP8LPrefixEncodeNoLUT.

extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];

extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];

static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,

                                             int* const extra_bits) {

  if (distance < PREFIX_LOOKUP_IDX_MAX) {

    const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];

    *code = prefix_code.code_;

    *extra_bits = prefix_code.extra_bits_;

  } else {

    VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits);

  }

}

static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,

                                         int* const extra_bits,

                                         int* const extra_bits_value) {

  if (distance < PREFIX_LOOKUP_IDX_MAX) {

    const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];

    *code = prefix_code.code_;

    *extra_bits = prefix_code.extra_bits_;

    *extra_bits_value = kPrefixEncodeExtraBitsValue[distance];

  } else {

    VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value);

  }

}

// Sum of each component, mod 256.

static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE

uint32_t VP8LAddPixels(uint32_t a, uint32_t b) {

  const uint32_t alpha_and_green = (a & 0xff00ff00u) + (b & 0xff00ff00u);

  const uint32_t red_and_blue = (a & 0x00ff00ffu) + (b & 0x00ff00ffu);

  return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);

}

// Difference of each component, mod 256.

static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE

uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {

  const uint32_t alpha_and_green =

      0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);

  const uint32_t red_and_blue =

      0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);

  return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);

}

//------------------------------------------------------------------------------

// Transform-related functions use din both encoding and decoding.

// Macros used to create a batch predictor that iteratively uses a

// one-pixel predictor.

// The predictor is added to the output pixel (which

// is therefore considered as a residual) to get the final prediction.

#define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD)             \

static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \

                          int num_pixels, uint32_t* out) {           \

  int x;                                                             \

  for (x = 0; x < num_pixels; ++x) {                                 \

    const uint32_t pred = (PREDICTOR)(out[x - 1], upper + x);        \

    out[x] = VP8LAddPixels(in[x], pred);                             \

  }                                                                  \

}

// It subtracts the prediction from the input pixel and stores the residual

// in the output pixel.

#define GENERATE_PREDICTOR_SUB(PREDICTOR, PREDICTOR_SUB)             \

static void PREDICTOR_SUB(const uint32_t* in, const uint32_t* upper, \

                          int num_pixels, uint32_t* out) {           \

  int x;                                                             \

  for (x = 0; x < num_pixels; ++x) {                                 \

    const uint32_t pred = (PREDICTOR)(in[x - 1], upper + x);         \

    out[x] = VP8LSubPixels(in[x], pred);                             \

  }                                                                  \

}

#ifdef __cplusplus

}    // extern "C"

#endif

#endif  // WEBP_DSP_LOSSLESS_COMMON_H_