/*

 * 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/binary_codes_reader.h"

#include "aom_dsp/recenter.h"

#define read_primitive_quniform(r, n, ACCT_STR_NAME) \

  read_primitive_quniform_(r, n ACCT_STR_ARG(ACCT_STR_NAME))

#define read_primitive_subexpfin(r, n, k, ACCT_STR_NAME) \

  read_primitive_subexpfin_(r, n, k ACCT_STR_ARG(ACCT_STR_NAME))

static uint16_t read_primitive_quniform_(aom_reader *r,

                                         uint16_t n ACCT_STR_PARAM) {

  if (n <= 1) return 0;

  const int l = get_msb(n) + 1;

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

  const int v = aom_read_literal(r, l - 1, ACCT_STR_NAME);

  return v < m ? v : (v << 1) - m + aom_read_bit(r, ACCT_STR_NAME);

}

// Decode finite subexponential code that for a symbol v in [0, n-1] with

// parameter k

static uint16_t read_primitive_subexpfin_(aom_reader *r, uint16_t n,

                                          uint16_t k ACCT_STR_PARAM) {

  int i = 0;

  int mk = 0;

  while (1) {

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

    int a = (1 << b);

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

      return read_primitive_quniform(r, n - mk, ACCT_STR_NAME) + mk;

    }

    if (!aom_read_bit(r, ACCT_STR_NAME)) {

      return aom_read_literal(r, b, ACCT_STR_NAME) + mk;

    }

    i = i + 1;

    mk += a;

  }

  assert(0);

  return 0;

}

uint16_t aom_read_primitive_refsubexpfin_(aom_reader *r, uint16_t n, uint16_t k,

                                          uint16_t ref ACCT_STR_PARAM) {

  return inv_recenter_finite_nonneg(

      n, ref, read_primitive_subexpfin(r, n, k, ACCT_STR_NAME));

}