fix fatal error on lack of device on linux

.travis.yml

@@ -16,4 +16,4 @@ branches:
     - master
     - io
 before_install:
-  - sudo apt-get install libasound2 libasound2-dev alsa-utils
+  - sudo apt-get install libasound2 libasound2-dev

Rakefile

@@ -7,4 +7,3 @@ if defined? RSpec
   end
 end
 task default: :spec
-task test: :spec

doc/overview.txt

@@ -0,0 +1,34 @@
+Device
+  Abstracts physical devices
+  it can be opened
+  it can be closed
+  it can be written to
+    in that you write to its buffer
+  it can be flushed
+    in that its buffer is flushed
+  it can be played
+    in that its buffer is written to and immediately flushed
+  you can write any Data to it
+  it has a identification
+
+Data
+  Abstracts real world sound data
+  it can have various formats
+  it can be writte to a device
+  it can have data which corresponds to its format
+
+Format
+  Abstracts real world data interpretation
+  it can be PCM or MIDI
+  if it's PCM
+    it has a sample rate
+    it is has some number of channels
+    it has a bit depth per sample
+    it has a bit rate per second
+  if it's MIDI
+    I have no idea what MIDI looks like
+
+
+Consider extending corresponding class to platform in lib/sound.rb
+so that in lib/sound/device.rb I can write open(args) instead of Win32::PCM.open
+I like this because it takes away platfrom decision logic from Sound::Device.

lib/sound.rb

@@ -6,6 +6,10 @@
 if OS.windows?
   require 'sound/win32/sound'
 elsif OS.linux?
+  libasound_present = `which aplay`.eql? ""
+  unless libasound_present
+    warn("warning: sound output requires libasound2 and libasound2-dev packages")
+  end
   require 'sound/linux/sound'
 else
   warn("warning: Sound output not yet implemented for this platform: #{OS.os}")

lib/sound/device.rb

@@ -2,17 +2,16 @@
 module Sound
 
   @verbose = false
-  @testing = false
+  @no_device = false
 
   class << self
-    attr_accessor :verbose, :testing
-    def testing?
-      testing
-    end
+    attr_accessor :verbose, :no_device
   end
 
   WAVE_MAPPER = -1
 
+  class NoDeviceError < RuntimeError; end
+
   class Device
 
     class Handle
@@ -44,7 +43,6 @@ class Buffer < Array; end
     attr_accessor :closed, :id, :handle, :format
 
     def initialize(direction = "w", id = nil, &block)
-
       if OS.windows?
         id ||= WAVE_MAPPER
       elsif OS.linux?
@@ -105,9 +103,7 @@ def write(data = "beep boop")
         @queue << Thread.new do
           Thread.current[:async] = false
           Thread.current[:data] = data
-          unless Sound.testing?
-            write_thread
-          end
+          write_thread
         end
         @mutex.unlock
         puts "writing to queue of device '#{id}': #{data}" if Sound.verbose
@@ -154,19 +150,17 @@ def close
     def flush
       until @queue.empty?
         output = @queue.shift
-        unless Sound.testing?
-          if output.kind_of? Thread
-            output[:stop] = false
-            puts "writing to device '#{id}': #{output[:data].class}" if Sound.verbose
-            output.run.join
-          else
-            output.each do |thread|
-              thread[:stop] = false
-              puts "writing to device '#{id}': #{thread[:data].class}" if Sound.verbose
-              thread.run
-            end
-            output.last.join if output.last.alive?
+        if output.kind_of? Thread
+          output[:stop] = false
+          puts "writing to device '#{id}': #{output[:data].class}" if Sound.verbose
+          output.run.join
+        else
+          output.each do |thread|
+            thread[:stop] = false
+            puts "writing to device '#{id}': #{thread[:data].class}" if Sound.verbose
+            thread.run
           end
+          output.last.join if output.last.alive?
         end
       end
     end
@@ -181,10 +175,14 @@ def write_thread
       Thread.current[:stop] = true if Thread.current[:stop].nil?
       if OS.windows? || OS.linux?
         open_device
-        prepare_buffer
+        unless Sound.no_device
+          prepare_buffer
+        end
         Thread.stop if Thread.current[:stop]
-        write_to_device
-        close_device
+        unless Sound.no_device
+          write_to_device
+          close_device
+        end
       else
         warn("warning: playback is not yet supported on this platform")
       end
@@ -194,7 +192,11 @@ def open_device
       if OS.windows?
         Win32::Sound.waveOutOpen(handle.pointer, id, data.format.pointer, 0, 0, 0)
       elsif OS.linux?
-        ALSA::PCM.open(handle.pointer, id, 0, ALSA::PCM::ASYNC)
+        begin
+          ALSA::PCM.open(handle.pointer, id, 0, ALSA::PCM::ASYNC)
+        rescue NoDeviceError
+          Sound.no_device = true
+        end
       end
     end
 
@@ -205,18 +207,16 @@ def prepare_buffer
 
         buffer_length
 
-        params = FFI::MemoryPointer.new(:pointer)
+        ALSA::PCM.params_malloc(params_handle.pointer)
+        ALSA::PCM.params_any(handle.id, params_handle.id)
 
-        ALSA::PCM.params_malloc(params)
-        ALSA::PCM.params_any(handle.id, params.read_pointer)
+        ALSA::PCM.set_access(handle.id, params_handle.id, ALSA::PCM::SND_PCM_ACCESS_RW_INTERLEAVED)
+        ALSA::PCM.set_format(handle.id, params_handle.id, ALSA::PCM::SND_PCM_FORMAT_S16_LE)
+        ALSA::PCM.set_rate(handle.id, params_handle.id, data.format.sample_rate, 0)
+        ALSA::PCM.set_channels(handle.id, params_handle.id, 1)
 
-        ALSA::PCM.set_access(handle.id, params.read_pointer, ALSA::PCM::SND_PCM_ACCESS_RW_INTERLEAVED)
-        ALSA::PCM.set_format(handle.id, params.read_pointer, ALSA::PCM::SND_PCM_FORMAT_S16_LE)
-        ALSA::PCM.set_rate(handle.id, params.read_pointer, data.format.sample_rate, 0)
-        ALSA::PCM.set_channels(handle.id, params.read_pointer, 1)
-
-        ALSA::PCM.save_params(handle.id, params.read_pointer)
-        ALSA::PCM.free_params(params.read_pointer)
+        ALSA::PCM.save_params(handle.id, params_handle.id)
+        ALSA::PCM.free_params(params_handle.id)
 
         ALSA::PCM.prepare(handle.id)
 
@@ -244,6 +244,10 @@ def handle
       Thread.current[:handle] ||= Handle.new
     end
 
+    def params_handle
+      Thread.current[:params_handle] ||= Handle.new
+    end
+
     def data
       Thread.current[:data]
     end

lib/sound/linux/sound.rb

@@ -13,7 +13,7 @@ class PCM
       ffi_lib 'asound'
       ffi_convention :stdcall
 
-      attach_function :open, :snd_pcm_open, [:pointer, :string, :int, :int], :int
+      attach_function :snd_pcm_open, [:pointer, :string, :int, :int], :int
       attach_function :close, :snd_pcm_close, [:pointer], :int
       attach_function :drain, :snd_pcm_drain, [:pointer], :int
       attach_function :prepare, :snd_pcm_prepare, [:pointer], :int
@@ -124,6 +124,14 @@ class PCM
       SND_PCM_ACCESS_RW_NONINTERLEAVED = 4
       SND_PCM_ACCESS_LAST = SND_PCM_ACCESS_RW_NONINTERLEAVED
 
+      def self.open(*args)
+        output = `aplay -l 2>&1`
+        if output.match(/no soundcard/m)
+          raise NoDeviceError, "No sound devices present"
+        else
+          snd_pcm_open(args)
+        end
+      end
     end
   end
 end

lib/sound/win32/sound.rb

@@ -16,6 +16,7 @@ class Sound
       attach_function :waveOutWrite, [:hwaveout, :pointer, :uint], :mmresult
       attach_function :waveOutUnprepareHeader, [:hwaveout, :pointer, :uint], :mmresult
       attach_function :waveOutClose, [:hwaveout], :mmresult
+
     end
 
     WAVE_FORMAT_PCM = 1

spec/spec_helper.rb

@@ -1,2 +1 @@
-require 'sound'
-Sound.testing = true
+require 'sound'