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postgrex

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PostgreSQL driver for Elixir

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postgrex lib postgrex extensions array.ex
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lib/postgrex/extensions/array.ex 

defmodule Postgrex.Extensions.Array do

  @moduledoc false

  alias Postgrex.TypeInfo

  alias Postgrex.Types

  import Postgrex.BinaryUtils

  use Postgrex.BinaryExtension, [] # send: "array_send" hard coded in types



  def encode(%TypeInfo{array_elem: elem_oid}, list, types, _) when is_list(list),

    do: encode_array(list, elem_oid, types)

  def encode(type_info, value, _, _) do

    raise ArgumentError, Postgrex.Utils.encode_msg(type_info, value, "a list")

  end



  def decode(_, bin, types, _),

    do: decode_array(bin, types)



  ## Helpers



  defp encode_array(list, elem_oid, types) do

    encoder = &Types.encode(elem_oid, &1, types)



    {data, ndims, lengths} = encode_array(list, 0, [], encoder)

    lengths = for len <- Enum.reverse(lengths), do: <<len :: int32, 1 :: int32>>

    [<<ndims :: int32, 0 :: int32, elem_oid :: uint32>>, lengths, data]

  end



  defp encode_array([], ndims, lengths, _encoder) do

    {"", ndims, lengths}

  end



  defp encode_array([head|tail]=list, ndims, lengths, encoder)

  when is_list(head) do

    lengths = [length(list)|lengths]

    {data, ndims, lengths} = encode_array(head, ndims, lengths, encoder)

    [dimlength|_] = lengths



    rest = Enum.reduce(tail, [], fn sublist, acc ->

      {data, _, [len|_]} = encode_array(sublist, ndims, lengths, encoder)

      if len != dimlength do

        raise ArgumentError, "nested lists must have lists with matching lengths"

      end

        [acc|data]

      end)



    {[data|rest], ndims+1, lengths}

  end



  defp encode_array(list, ndims, lengths, encoder) do

    {data, length} =

    Enum.map_reduce(list, 0, fn

      nil, length ->

        {<<-1::int32>>, length + 1}

      elem, length ->

        data = encoder.(elem)

        data = [<<IO.iodata_length(data)::int32>>, data]

        {data, length + 1}

    end)

    {data, ndims+1, [length|lengths]}

  end



  defp decode_array(<<ndims :: int32, _has_null :: int32, oid :: uint32,

                      dims :: size(ndims)-binary-unit(64), rest :: binary>>, types) do

    lengths = for <<len :: int32, _lbound :: int32 <- dims>>, do: len

    decoder = &Types.decode(oid, &1, types)



    {array, ""} = decode_array(rest, lengths, decoder)

    array

  end



  defp decode_array("", [], _decoder) do

    {[], ""}

  end



  defp decode_array(rest, [len], decoder) do

    array_elements(rest, len, [], decoder)

  end



  defp decode_array(rest, [len|lens], decoder) do

    Enum.map_reduce(1..len, rest, fn _, rest ->

      decode_array(rest, lens, decoder)

    end)

  end



  defp array_elements(rest, 0, acc, _decoder) do

    {Enum.reverse(acc), rest}

  end



  defp array_elements(<<-1 :: int32, rest :: binary>>, count, acc, decoder) do

    array_elements(rest, count-1, [nil|acc], decoder)

  end



  defp array_elements(<<size :: int32, elem :: binary(size), rest :: binary>>,

                       count, acc, decoder) do

    value = decoder.(elem)

    array_elements(rest, count-1, [value|acc], decoder)

  end

end