/* The copyright in this software is being made available under the BSD
 * Licence, included below.  This software may be subject to other third
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 * Copyright (c) 2017-2018, ISO/IEC
 * All rights reserved.
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 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
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 * * Redistributions in binary form must reproduce the above copyright
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 *   may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 */

#include "entropydirac.h"

#include "PCCMisc.h"

#include <algorithm>

namespace pcc {
namespace dirac {

  //=========================================================================

  void SchroMAryContext::set_alphabet(int numsyms)
  {
    // initialise all contexts with p = 0.5
    this->numsyms = numsyms;
    this->probabilities = std::vector<uint16_t>(numsyms, 0x8000);
  }

  //=========================================================================

  void ArithmeticEncoder::encode(int sym, SchroMAryContext& model)
  {
    int ctxidx = 0;

    while (sym-- > 0) {
      schro_arith_encode_bit(&impl, &model.probabilities[ctxidx++], 1);
    }
    // todo(df): this should be truncated unary coded
    schro_arith_encode_bit(&impl, &model.probabilities[ctxidx], 0);
  }

  //=========================================================================

  int ArithmeticDecoder::decode(SchroMAryContext& model)
  {
    int ctxidx = 0;
    int sym = 0;

    while (schro_arith_decode_bit(&impl, &model.probabilities[ctxidx++])) {
      sym++;
    }

    return sym;
  }

  //==========================================================================

}  // namespace dirac
}  // namespace pcc
