source/splitfx: restart source on YAML modifications

Since splitfx YAML files are intended to be frequently edited and
modified by the user, we'll support automatically restarting the
source when the user saves changes via their favorite $EDITOR

This change is only for Linux users.  However, sleepy_penguin
supports kqueue nowadays so a patch to support such functionality
would be appreciated.

2 files changed, 56 insertions, 0 deletions

diff --git a/lib/dtas/source/splitfx.rb b/lib/dtas/source/splitfx.rb
index ad9e7c1..a0899f3 100644
--- a/lib/dtas/source/splitfx.rb
+++ b/lib/dtas/source/splitfx.rb
@@ -3,10 +3,12 @@
 require 'yaml'
 require_relative 'sox'
 require_relative '../splitfx'
+require_relative 'watchable'
 
 class DTAS::Source::SplitFX < DTAS::Source::Sox # :nodoc:
   MAX_YAML_SIZE = 512 * 1024
   attr_writer :sox
+  include DTAS::Source::Watchable if defined?(DTAS::Source::Watchable)
 
   SPLITFX_DEFAULTS = SOX_DEFAULTS.merge("tryorder" => 3)
 
diff --git a/lib/dtas/source/watchable.rb b/lib/dtas/source/watchable.rb
new file mode 100644
index 0000000..3ff9ef8
--- /dev/null
+++ b/lib/dtas/source/watchable.rb
@@ -0,0 +1,54 @@
+# Copyright (C) 2014, all contributors <dtas-all@nongnu.org>
+# License: GPLv3 or later <https://www.gnu.org/licenses/gpl-3.0.txt>
+begin
+  require 'sleepy_penguin'
+rescue LoadError
+end
+
+# used to restart DTAS::Source::SplitFX processing in dtas-player
+# if the YAML file is edited
+module DTAS::Source::Watchable
+  class InotifyReadableIter < SleepyPenguin::Inotify
+    def self.new
+      super(:CLOEXEC)
+    end
+
+    FLAGS = CLOSE_WRITE | MOVED_TO
+
+    def readable_iter
+      or_call = false
+      while event = take(true) # drain the buffer
+        if (event.mask & FLAGS) != 0 && @watching[1] == event.name
+          or_call = true
+        end
+      end
+      if or_call && @on_readable
+        @on_readable.call
+        :delete
+      else
+        :wait_readable
+      end
+    end
+
+    # we must watch the directory, since
+    def watch_file(path, blk)
+      @on_readable = blk
+      @watching = File.split(File.expand_path(path))
+      add_watch(@watching[0], FLAGS)
+    end
+  end
+
+  def watch_begin(blk)
+    @ino = InotifyReadableIter.new
+    @ino.watch_file(@infile, blk)
+    @ino
+  end
+
+  # Closing the inotify descriptor (instead of using inotify_rm_watch)
+  # is cleaner because it avoids EINVAL on race conditions in case
+  # a directory is deleted: https://lkml.org/lkml/2007/7/9/3
+  def watch_end(srv)
+    srv.wait_ctl(@ino, :delete)
+    @ino = @ino.close
+  end
+end if defined?(SleepyPenguin::Inotify)