waveOutOpen

I have successfully made a library call to waveOutOpen!

require 'ffi'

module WaveOutWrapper

  WAVE_FORMAT_PCM = 1
  WAVE_MAPPER = -1

  class WAVEFORMATEX < FFI::Struct

    def initialize(nSamplesPerSec, wBitsPerSample, nChannels, cbSize)
      self[:nSamplesPerSec] = nSamplesPerSec
      self[:wBitsPerSample] = wBitsPerSample
      self[:nChannels] = nChannels
      self[:cbSize] = cbSize
      self[:wFormatTag] = WAVE_FORMAT_PCM
      self[:nBlockAlign] = (self[:wBitsPerSample] >> 3) * self[:nChannels]
      self[:nAvgBytesPerSec] = self[:nBlockAlign] * self[:nSamplesPerSec]
    end

    layout :wFormatTag,      :ushort,
           :nChannels,       :ushort,
           :nSamplesPerSec,  :ulong, 
           :nAvgBytesPerSec, :ulong, 
           :nBlockAlign,     :ushort,
           :wBitsPerSample,  :ushort,
           :cbSize,          :ushort
    
  end

  class Sound
    extend FFI::Library
    
    private
    
    typedef :uint, :mmresult
    typedef :ulong, :dword
    
    ffi_lib :winmm
    
    attach_function :waveOutOpen, [:pointer, :uint, :pointer, :dword, :dword, :dword], :mmresult
    attach_function :waveOutClose, [:pointer], :mmresult
    
    public
    
    def self.play
    
      hWaveOut = FFI::MemoryPointer.new(:int)
      wfx = WAVEFORMATEX.new(44100, 16, 2, 0)
      waveOutOpenResult = waveOutOpen(hWaveOut, WAVE_MAPPER, wfx.pointer, 0, 0, 0)
      raise SystemCallError, FFI.errno, "waveOutOpen didn't work: #{waveOutOpenResult}" if waveOutOpenResult != 0
      waveOutClose(hWaveOut)
      
      self
    end

  end

end

WaveOutWrapper::Sound.play # this won't actually play anything, but it doesn't return an error!