danicoin/src/mnemonics/language_base.h

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/*!
 * \file language_base.h
 * 
 * \brief Language Base class for Polymorphism.
 */

#ifndef LANGUAGE_BASE_H
#define LANGUAGE_BASE_H

#include <vector>
#include <unordered_map>
#include <string>

/*!
 * \namespace Language
 * \brief Mnemonic language related namespace.
 */
namespace Language
{
  /*!
   * \brief Returns a string made of (at most) the first count characters in s.
   *        Assumes well formedness. No check is made for this.
   * \param  s               The string from which to return the first count characters.
   * \param  count           How many characters to return.
   * \return                 A string consisting of the first count characters in s.
   */
  inline std::string utf8prefix(const std::string &s, size_t count)
  {
    std::string prefix = "";
    const char *ptr = s.c_str();
    while (count-- && *ptr)
    {
      prefix += *ptr++;
      while (((*ptr) & 0xc0) == 0x80)
        prefix += *ptr++;
    }
    return prefix;
  }

  /*!
   * \class Base
   * \brief A base language class which all languages have to inherit from for
   * Polymorphism.
   */
  class Base
  {
  protected:
    std::vector<std::string> *word_list; /*!< A pointer to the array of words */
    std::unordered_map<std::string, uint32_t> *word_map; /*!< hash table to find word's index */
    std::unordered_map<std::string, uint32_t> *trimmed_word_map; /*!< hash table to find word's trimmed index */
    std::string language_name; /*!< Name of language */
    uint32_t unique_prefix_length; /*!< Number of unique starting characters to trim the wordlist to when matching */
    /*!
     * \brief Populates the word maps after the list is ready.
     */
    void populate_maps()
    {
      int ii;
      std::vector<std::string>::iterator it;
      for (it = word_list->begin(), ii = 0; it != word_list->end(); it++, ii++)
      {
        (*word_map)[*it] = ii;
        if (it->length() > unique_prefix_length)
        {
          (*trimmed_word_map)[utf8prefix(*it, unique_prefix_length)] = ii;
        }
        else
        {
          (*trimmed_word_map)[*it] = ii;
        }
      }
    }
  public:
    Base()
    {
      word_list = new std::vector<std::string>;
      word_map = new std::unordered_map<std::string, uint32_t>;
      trimmed_word_map = new std::unordered_map<std::string, uint32_t>;
      unique_prefix_length = 4;
    }
    /*!
     * \brief Returns a pointer to the word list.
     * \return A pointer to the word list.
     */
    const std::vector<std::string>& get_word_list() const
    {
      return *word_list;
    }
    /*!
     * \brief Returns a pointer to the word map.
     * \return A pointer to the word map.
     */
    const std::unordered_map<std::string, uint32_t>& get_word_map() const
    {
      return *word_map;
    }
    /*!
     * \brief Returns a pointer to the trimmed word map.
     * \return A pointer to the trimmed word map.
     */
    const std::unordered_map<std::string, uint32_t>& get_trimmed_word_map() const
    {
      return *trimmed_word_map;
    }
    /*!
     * \brief Returns the name of the language.
     * \return Name of the language.
     */
    std::string get_language_name() const
    {
      return language_name;
    }
    /*!
     * \brief Returns the number of unique starting characters to be used for matching.
     * \return Number of unique starting characters.
     */
    uint32_t get_unique_prefix_length() const
    {
      return unique_prefix_length;
    }
  };
}

#endif