One liner music player for Ruby. http://hitode909.appspot.com/one-liner-music/

olm.rb

require 'rubygems'
require 'ffi-portaudio'

def safe
  r = nil
  Thread.new {
    $SAFE = 4
    r = yield
  }.join
  r
end

class OLMStream < FFI::PortAudio::Stream
  attr_accessor :generator

  def initialize
    @count = 0
    @max = 1
  end

  def process(input, output, frameCount, timeInfo, statusFlags, userData)
    wave = (0...frameCount).map{|i|@generator.call(@count+=1)}
    @max = [wave.max, @max].max
    volume = 0x8000.quo @max
    output.write_array_of_int16 wave.map!{|v| v * volume}

    :paContinue
  end
end

include FFI::PortAudio

API.Pa_Initialize

output = API::PaStreamParameters.new
output[:device] = API.Pa_GetDefaultOutputDevice
output[:channelCount] = 1
output[:sampleFormat] = API::Int16
output[:suggestedLatency] = 0.2
output[:hostApiSpecificStreamInfo] = nil

generator = ARGV.shift

s = OLMStream.new
s.generator = safe { eval "lambda {|t| #{generator} }" }
s.open(nil, output, 8000)
s.start

at_exit do
  s.close
  API.Pa_Terminate
end

loop { sleep 1 }