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Localization (parsing, formatting) of numbers, dates/time/calendar, units of measure, messages and lists. Includes localized collation.

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localize lib localize collation unicode.ex
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lib/localize/collation/unicode.ex 

defmodule Localize.Collation.Unicode do

  @moduledoc false



  # Provides Unicode Character Database lookups for the collation

  # system: canonical combining class and decimal digit detection.

  #

  # Data is loaded from pre-generated ETF files in

  # `priv/localize/supplemental_data/` and cached in

  # `:persistent_term` on first access.



  @combining_classes_key {:localize, :combining_classes}

  @decimal_digit_ranges_key {:localize, :decimal_digit_ranges}



  @doc false

  @spec combining_class(non_neg_integer()) :: non_neg_integer()

  def combining_class(codepoint) do

    classes = load_combining_classes()

    Map.get(classes, codepoint, 0)

  end



  @doc false

  @spec decimal_digit?(non_neg_integer()) :: boolean()

  def decimal_digit?(codepoint) do

    ranges = load_decimal_digit_ranges()

    in_ranges?(codepoint, ranges)

  end



  defp load_combining_classes do

    Localize.DataLoader.load(@combining_classes_key, fn ->

      load_etf("combining_classes.etf")

    end)

  end



  defp load_decimal_digit_ranges do

    Localize.DataLoader.load(@decimal_digit_ranges_key, fn ->

      load_etf("decimal_digit_ranges.etf")

    end)

  end



  defp load_etf(filename) do

    :localize

    |> Application.app_dir(["priv", "localize", "supplemental_data", filename])

    |> File.read!()

    |> :erlang.binary_to_term()

  end



  # Binary search over sorted {start, finish} ranges.

  defp in_ranges?(codepoint, ranges) do

    binary_search(codepoint, ranges, 0, length(ranges) - 1)

  end



  defp binary_search(_cp, _ranges, low, high) when low > high, do: false



  defp binary_search(cp, ranges, low, high) do

    mid = div(low + high, 2)

    {range_start, range_end} = Enum.at(ranges, mid)



    cond do

      cp < range_start -> binary_search(cp, ranges, low, mid - 1)

      cp > range_end -> binary_search(cp, ranges, mid + 1, high)

      true -> true

    end

  end

end