iroha.exs

defmodule FormChunk do
  defstruct [:id, :size, :type, :common, :sound_data]
  
  def new(
    << 
    id     :: bitstring-size(32), 
    size   :: unsigned-integer-size(32),
    type   :: bitstring-size(32),    
    chunks :: binary,
    >>) do

    ## Common Chunk のメタデータを抽出
    <<
    common_id         :: unsigned-integer-size(32), 
    common_chunk_size :: unsigned-integer-size(32),
    remain            :: binary
    >> = chunks

    ## 抽出された値で Common Chunk と Sound Data Chunk を分ける
    <<
    common_data       :: binary-size(common_chunk_size),
    sound_data_chunk  :: binary
    >> = remain
    
    %FormChunk{
      id:         id,
      size:       size,
      type:       type,
      common:     CommonChunk.new(common_id, common_chunk_size, common_data),
      sound_data: SoundDataChunk.new(sound_data_chunk)
    }
  end
end

defmodule CommonChunk do
  defstruct [
    :id, 
    :size, 
    :num_channels, 
    :num_sample_frames,
    :sample_size,
    :sample_rate,
  ]

  def new(
    id,
    size,
    <<
    num_channels      :: unsigned-integer-size(16),
    num_sample_frames :: unsigned-integer-size(32),
    sample_size       :: unsigned-integer-size(16),

    # FIXME: Sound Rate よく分からん
    _x                :: unsigned-integer-size(16), # ?
    sample_rate       :: unsigned-integer-size(16), # hmm...
    _y                :: binary                     
    >>) do
    
    %CommonChunk{
      id: id,
      size: size,
      num_channels: num_channels,
      num_sample_frames: num_sample_frames,
      sample_size: sample_size,
      sample_rate: sample_rate,
    }
  end
end

defmodule SoundDataChunk do
  defstruct [
    :id,
    :size,
    :offset,
    :block_size,
    :sound_data,
  ]

  def new(
    <<
    id         :: bitstring-size(32),
    size       :: unsigned-integer-size(32),
    offset     :: unsigned-integer-size(32),
    block_size :: unsigned-integer-size(32),
    sound_data :: binary
    >>) do
    
    %SoundDataChunk{
      id: id,
      size: size,
      offset: offset,
      block_size: block_size,
      sound_data: sound_data,
    }
  end
end

[path] = System.argv

{:ok, file} = File.open path, [:read]
IO.inspect FormChunk.new IO.binread(file, :all)
File.close file