watcher-rb: gradually getting there

watcher-rb/Gemfile

@@ -4,6 +4,8 @@ source 'https://rubygems.org'
 
 gemspec
 
+gem 'ffi'
+gem 'fiddle'
 gem 'rake'
 gem 'rspec'
 gem 'solargraph'

watcher-rb/Gemfile.lock

@@ -2,6 +2,7 @@ PATH
   remote: .
   specs:
     watcher (0.11.0)
+      ffi
 
 GEM
   remote: https://rubygems.org/
@@ -11,6 +12,8 @@ GEM
     benchmark (0.3.0)
     diff-lcs (1.5.1)
     e2mmap (0.1.0)
+    ffi (1.17.0-arm64-darwin)
+    fiddle (1.1.2)
     jaro_winkler (1.6.0)
     json (2.7.2)
     kramdown (2.4.0)
@@ -102,6 +105,8 @@ PLATFORMS
 
 DEPENDENCIES
   bundler (~> 2.0)
+  ffi
+  fiddle
   rake
   rspec
   solargraph

watcher-rb/Rakefile

@@ -1,20 +1,24 @@
 # frozen_string_literal: true
 
-require "bundler/gem_tasks"
-require "rspec/core/rake_task"
+require 'bundler/gem_tasks'
+require 'rspec/core/rake_task'
 
 RSpec::Core::RakeTask.new(:spec)
 
-task build_shared_library: ["lib"] do
-  framework_deps = case RbConfig::CONFIG["host_os"]
+task build_shared_library: ['lib'] do
+  case RbConfig::CONFIG['host_os']
   when /darwin/
-    "-framework CoreServices -framework CoreFoundation"
+    framework_deps = '-framework CoreServices -framework CoreFoundation'
+    link_rpath = '-Wl,-rpath,/usr/local/lib'
   else
-    ""
+    framework_deps = ''
+    link_rpath = ''
   end
-  version = File.read("../.version").strip
+  version = File.read('../.version').strip
   libname = "libwatcher-c-#{version}.so"
-  sh "c++ -shared -std=c++17 -O2 #{framework_deps} ../watcher-c/src/watcher-c.cpp -I ../watcher-c/include -o lib/#{libname}"
+  sources = '../watcher-c/src/watcher-c.cpp'
+  includes = '../watcher-c/include'
+  sh "c++ -shared -std=c++17 -O2 #{framework_deps} #{sources} -I #{includes} -o lib/#{libname} #{link_rpath}"
 end
 
-task default: [:clobber, :build_shared_library, :spec]
+task default: %i[clobber build_shared_library spec]

watcher-rb/lib/watcher.rb

@@ -1,57 +1,36 @@
+# rubocop:disable Metrics/MethodLength
+# rubocop:disable Style/Documentation
 # frozen_string_literal: true
 
-require 'fiddle'
 require 'date'
+require 'fiddle'
+require 'fiddle/closure'
+require 'fiddle/cparser'
+require 'fiddle/import'
+require 'fiddle/struct'
 
 module Watcher
-  class CEvent < Fiddle::Struct
-    layout(
-      :path_name,
-      :pointer,
-      :effect_type,
-      :int8_t,
-      :path_type,
-      :int8_t,
-      :effect_time,
-      :int64_t,
-      :associated_path_name,
-      :pointer
-    )
-  end
-
-  LIB = nil
-
-  def native_solib_file_ending
-    case RbConfig::CONFIG['host_os']
-    when /darwin/
-      'so'
-    when /mswin|mingw|cygwin/
-      'dll'
-    else
-      'so'
-    end
-  end
+  C_EVENT_DATA = [
+    'char* path_name',
+    'int8_t effect_type',
+    'int8_t path_type',
+    'int64_t effect_time',
+    'char* associated_path_name'
+  ].freeze
 
-  def libwatcher_c_lib_path
-    version = '0.11.0' # hook: tool/release
-    lib_name = "libwatcher-c-#{version}.#{native_solib_file_ending}"
-    lib_path = File.join(File.dirname(__FILE__), lib_name)
-    raise "Library does not exist: '#{lib_path}'" unless File.exist?(lib_path)
+  C_EVENT = Fiddle::Importer.struct(C_EVENT_DATA)
 
-    puts("Using library: '#{lib_path}'")
-    lib_path
-  end
+  C_EVENT_C_TYPE = Fiddle::Importer.parse_struct_signature(C_EVENT_DATA)
 
-  def self.lazy_static_solib_handle
-    return LIB if LIB
+  # Wraps: void (* wtr_watcher_callback)(struct wtr_watcher_event event, void* context)
 
-    @lib = Fiddle.dlopen(libwatcher_c_lib_path)
-    @lib.extern('void* wtr_watcher_open(char*, void*, void*)')
-    @lib.extern('bool wtr_watcher_close(void*)')
-    @lib
-  end
+  C_CALLBACK_BRIDGE_CLOSURE = Class.new(Fiddle::Closure) {
+    def call(c_event, rb_cb)
+      rb_cb.call(Watcher.c_event_to_event(c_event))
+    end
+  }.new(Fiddle::TYPE_VOID, [Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP])
 
-  def to_utf8
+  def self.to_utf8
     return '' if @value.nil?
     return @value if @value.is_a?(String)
     return @value.to_s.force_encoding('UTF-8') if @value.respond_to?(:to_s)
@@ -133,8 +112,6 @@ def to_s
   end
 
   class Event
-    attr_reader :path_name, :effect_type, :path_type, :effect_time, :associated_path_name
-
     def initialize(path_name, effect_type, path_type, effect_time, associated_path_name)
       @path_name = path_name
       @effect_type = effect_type
@@ -155,23 +132,46 @@ def to_s
 
   class Watch
     def initialize(path, callback)
-      @lib = Watcher.lazy_static_solib_handle
-      @path = path.encode('UTF-8')
-      @callback = callback
-      @c_callback = Fiddle::Closure::BlockCaller.new(0, [CEvent, :void]) do |c_event, _|
-        py_event = Watcher.c_event_to_event(c_event)
-        @callback.call(py_event)
-      end
-
-      @watcher = @lib.wtr_watcher_open(@path, @c_callback, nil)
-      raise 'Failed to open a watcher' unless @watcher
+      native_solib_file_ending =
+        case RbConfig::CONFIG['host_os']
+        when /darwin/
+          'so'
+        when /mswin|mingw|cygwin/
+          'dll'
+        else
+          'so'
+        end
+      version = '0.11.0' # hook: tool/release
+      lib_name = "libwatcher-c-#{version}.#{native_solib_file_ending}"
+      lib_path = File.join(File.dirname(__FILE__), lib_name)
+      puts("Using library: '#{lib_path}'")
+      @_path = path.encode('UTF-8')
+      @_callback = callback
+      @_lib = Fiddle.dlopen(lib_path)
+      @_wtr_watcher_open = Fiddle::Function.new(
+        @_lib['wtr_watcher_open'],
+        [Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP],
+        Fiddle::TYPE_VOIDP
+      )
+      @_wtr_watcher_close = Fiddle::Function.new(
+        @_lib['wtr_watcher_close'],
+        [Fiddle::TYPE_VOIDP],
+        Fiddle::TYPE_VOIDP
+      )
+      @_c_callback_bridge = Fiddle::Function.new(
+        C_CALLBACK_BRIDGE_CLOSURE,
+        [Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP],
+        Fiddle::TYPE_VOID
+      )
+      @_watcher = @_wtr_watcher_open.call(@_path, @_c_callback_bridge, @_callback)
+      raise 'Failed to open a watcher' unless @_watcher
     end
 
     def close
-      return unless @watcher
+      return unless _watcher
 
-      @lib.wtr_watcher_close(@watcher)
-      @watcher = nil
+      _wtr_watcher_close(_watcher)
+      _watcher = nil
     end
 
     def finalize
@@ -190,3 +190,6 @@ def self.finalize(id)
   ObjectSpace.define_finalizer(watcher, Watcher::Watch.method(:finalize).to_proc)
   gets
 end
+
+# rubocop:enable Style/Documentation
+# rubocop:enable Metrics/MethodLength

watcher-rb/watcher.gemspec

@@ -17,6 +17,7 @@ Gem::Specification.new do |spec|
   spec.bindir = 'bin'
   spec.executables = 'watcher'
   spec.require_paths = ['lib']
+  spec.add_dependency 'ffi'
   spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_development_dependency 'rake', '~> 13.0'
   spec.add_development_dependency 'rspec', '~> 3.0'