watchable: use fiddle for inotify support

We have String#unpack at our disposal for working with "struct
inotify_event", so use it instead of depending on an extension
which requires a compiler and development headers to install.

2 files changed, 91 insertions, 0 deletions

diff --git a/lib/dtas/watchable/fiddle_ino.rb b/lib/dtas/watchable/fiddle_ino.rb
new file mode 100644
index 0000000..3b9d668
--- /dev/null
+++ b/lib/dtas/watchable/fiddle_ino.rb
@@ -0,0 +1,78 @@
+# Copyright (C) 2013-2019 all contributors <dtas-all@nongnu.org>
+# License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
+# frozen_string_literal: true
+require 'fiddle'
+
+# used to restart DTAS::Source::SplitFX processing in dtas-player
+# if the YAML file is edited
+class DTAS::Watchable::InotifyReadableIter # :nodoc:
+  include DTAS::Watchable::InotifyCommon
+
+  Inotify_init = Fiddle::Function.new(DTAS.libc['inotify_init1'],
+    [ Fiddle::TYPE_INT ],
+    Fiddle::TYPE_INT)
+
+  Inotify_add_watch = Fiddle::Function.new(DTAS.libc['inotify_add_watch'],
+    [ Fiddle::TYPE_INT, Fiddle::TYPE_VOIDP, Fiddle::TYPE_INT ],
+    Fiddle::TYPE_INT)
+
+  # IO.select compatibility
+  attr_reader :to_io  #:nodoc:
+
+  def initialize # :nodoc:
+    fd = Inotify_init.call(02000000 | 04000) # CLOEXEC | NONBLOCK
+    raise "inotify_init failed: #{Fiddle.last_error}" if fd < 0
+    @to_io = DTAS::Nonblock.for_fd(fd)
+    @buf = ''.b
+    @q = []
+  end
+
+  # struct inotify_event {
+  #     int      wd;       /* Watch descriptor */
+  #     uint32_t mask;     /* Mask describing event */
+  #     uint32_t cookie;   /* Unique cookie associating related
+  #                           events (for rename(2)) */
+  #     uint32_t len;      /* Size of name field */
+  #     char     name[];   /* Optional null-terminated name */
+  InotifyEvent = Struct.new(:wd, :mask, :cookie, :len, :name) # :nodoc:
+
+  def take(nonblock) # :nodoc:
+    event = @q.pop and return event
+    case rv = @to_io.read_nonblock(16384, @buf, exception: false)
+    when :wait_readable, nil
+      return
+    else
+      until rv.empty?
+        hdr = rv.slice!(0,16)
+        name = nil
+        wd, mask, cookie, len = res = hdr.unpack('iIII')
+        wd && mask && cookie && len or
+          raise "bogus inotify_event #{res.inspect} hdr=#{hdr.inspect}"
+        if len > 0
+          name = rv.slice!(0, len)
+          name.size == len or raise "short name #{name.inspect} != #{len}"
+          name.sub!(/\0+\z/, '') or
+            raise "missing: `\\0', inotify_event.name=#{name.inspect}"
+          name = DTAS.dedupe_str(name)
+        end
+        ie = InotifyEvent.new(wd, mask, cookie, len, name)
+        if event
+          @q << ie
+        else
+          event = ie
+        end
+      end # /until rv.empty?
+      return event
+    end while true
+  end
+
+  def add_watch(watchdir, flags)
+    wd = Inotify_add_watch.call(@to_io.fileno, watchdir, flags)
+    raise "inotify_add_watch failed: #{Fiddle.last_error}" if wd < 0
+    wd
+  end
+
+  def close
+    @to_io = @to_io.close if @to_io
+  end
+end
diff --git a/lib/dtas/watchable/inotify.rb b/lib/dtas/watchable/inotify.rb
new file mode 100644
index 0000000..eface0e
--- /dev/null
+++ b/lib/dtas/watchable/inotify.rb
@@ -0,0 +1,13 @@
+# Copyright (C) 2013-2019 all contributors <dtas-all@nongnu.org>
+# License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
+# frozen_string_literal: true
+require 'sleepy_penguin'
+
+# used to restart DTAS::Source::SplitFX processing in dtas-player
+# if the YAML file is edited
+class DTAS::Watchable::InotifyReadableIter < SleepyPenguin::Inotify # :nodoc:
+  include DTAS::Watchable::InotifyCommon
+  def self.new
+    super(:CLOEXEC)
+  end
+end