/*

 * Copyright (c) 2017, Alliance for Open Media. All rights reserved

 *

 * This source code is subject to the terms of the BSD 2 Clause License and

 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License

 * was not distributed with this source code in the LICENSE file, you can

 * obtain it at www.aomedia.org/license/software. If the Alliance for Open

 * Media Patent License 1.0 was not distributed with this source code in the

 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.

 */

#include "aom_dsp/bitwriter.h"

#include "aom_dsp/binary_codes_writer.h"

#include "aom_dsp/recenter.h"

#include "aom_ports/bitops.h"

// Codes a symbol v in [-2^mag_bits, 2^mag_bits].

// mag_bits is number of bits for magnitude. The alphabet is of size

// 2 * 2^mag_bits + 1, symmetric around 0, where one bit is used to

// indicate 0 or non-zero, mag_bits bits are used to indicate magnitide

// and 1 more bit for the sign if non-zero.

void aom_write_primitive_symmetric(aom_writer *w, int16_t v,

                                   unsigned int abs_bits) {

  if (v == 0) {

    aom_write_bit(w, 0);

  } else {

    const int x = abs(v);

    const int s = v < 0;

    aom_write_bit(w, 1);

    aom_write_bit(w, s);

    aom_write_literal(w, x - 1, abs_bits);

  }

}

int aom_count_primitive_symmetric(int16_t v, unsigned int abs_bits) {

  return (v == 0 ? 1 : abs_bits + 2);

}

// Encodes a value v in [0, n-1] quasi-uniformly

void aom_write_primitive_quniform(aom_writer *w, uint16_t n, uint16_t v) {

  if (n <= 1) return;

  const int l = get_msb(n) + 1;

  const int m = (1 << l) - n;

  if (v < m) {

    aom_write_literal(w, v, l - 1);

  } else {

    aom_write_literal(w, m + ((v - m) >> 1), l - 1);

    aom_write_bit(w, (v - m) & 1);

  }

}

int aom_count_primitive_quniform(uint16_t n, uint16_t v) {

  if (n <= 1) return 0;

  const int l = get_msb(n) + 1;

  const int m = (1 << l) - n;

  return v < m ? l - 1 : l;

}

// Finite subexponential code that codes a symbol v in [0, n-1] with parameter k

void aom_write_primitive_subexpfin(aom_writer *w, uint16_t n, uint16_t k,

                                   uint16_t v) {

  int i = 0;

  int mk = 0;

  while (1) {

    int b = (i ? k + i - 1 : k);

    int a = (1 << b);

    if (n <= mk + 3 * a) {

      aom_write_primitive_quniform(w, n - mk, v - mk);

      break;

    } else {

      int t = (v >= mk + a);

      aom_write_bit(w, t);

      if (t) {

        i = i + 1;

        mk += a;

      } else {

        aom_write_literal(w, v - mk, b);

        break;

      }

    }

  }

}

int aom_count_primitive_subexpfin(uint16_t n, uint16_t k, uint16_t v) {

  int count = 0;

  int i = 0;

  int mk = 0;

  while (1) {

    int b = (i ? k + i - 1 : k);

    int a = (1 << b);

    if (n <= mk + 3 * a) {

      count += aom_count_primitive_quniform(n - mk, v - mk);

      break;

    } else {

      int t = (v >= mk + a);

      count++;

      if (t) {

        i = i + 1;

        mk += a;

      } else {

        count += b;

        break;

      }

    }

  }

  return count;

}

// Finite subexponential code that codes a symbol v in [0, n-1] with parameter k

// based on a reference ref also in [0, n-1].

// Recenters symbol around r first and then uses a finite subexponential code.

void aom_write_primitive_refsubexpfin(aom_writer *w, uint16_t n, uint16_t k,

                                      uint16_t ref, uint16_t v) {

  aom_write_primitive_subexpfin(w, n, k, recenter_finite_nonneg(n, ref, v));

}

void aom_write_signed_primitive_refsubexpfin(aom_writer *w, uint16_t n,

                                             uint16_t k, int16_t ref,

                                             int16_t v) {

  ref += n - 1;

  v += n - 1;

  const uint16_t scaled_n = (n << 1) - 1;

  aom_write_primitive_refsubexpfin(w, scaled_n, k, ref, v);

}

int aom_count_primitive_refsubexpfin(uint16_t n, uint16_t k, uint16_t ref,

                                     uint16_t v) {

  return aom_count_primitive_subexpfin(n, k, recenter_finite_nonneg(n, ref, v));

}

int aom_count_signed_primitive_refsubexpfin(uint16_t n, uint16_t k, int16_t ref,

                                            int16_t v) {

  ref += n - 1;

  v += n - 1;

  const uint16_t scaled_n = (n << 1) - 1;

  return aom_count_primitive_refsubexpfin(scaled_n, k, ref, v);

}