// Copyright (c) Google LLC 2019

//

// Use of this source code is governed by an MIT-style

// license that can be found in the LICENSE file or at

// https://opensource.org/licenses/MIT.

// Library to decode the Huffman code lengths from the bit-stream and build a

// decoding table from them.

#ifndef BRUNSLI_DEC_HUFFMAN_DECODE_H_

#define BRUNSLI_DEC_HUFFMAN_DECODE_H_

#include <memory>

#include <vector>

#include "./huffman_table.h"

namespace brunsli {

struct BrunsliBitReader;

template<typename T>

struct Arena {

  size_t capacity = 0;

  // TODO(eustas): use "char" storage to ensure new[] does not initialize...

  std::unique_ptr<T[]> storage;

  void reserve(size_t limit) {

    if (capacity < limit) {

      capacity = limit;

      storage.reset(new T[capacity]);

    }

  }

  T* data() {

    return storage.get();

  }

  void reset() {

    capacity = 0;

    storage.reset();

  }

};

struct HuffmanDecodingData {

  // Decodes the Huffman code lengths from the bit-stream and fills in the

  // pre-allocated table with the corresponding 2-level Huffman decoding table.

  // |arena| is used as an intermediate output for BuildHuffmanTable.

  // Returns false if the Huffman code lengths can not de decoded.

  bool ReadFromBitStream(size_t alphabet_size, BrunsliBitReader* br,

                         Arena<HuffmanCode>* arena = nullptr);

  uint16_t ReadSymbol(BrunsliBitReader* br) const;

  std::vector<HuffmanCode> table_;

};

}  // namespace brunsli

#endif  // BRUNSLI_DEC_HUFFMAN_DECODE_H_