Use reference instead of primitive

src/library/library.cr

@@ -143,10 +143,10 @@ class Library
     storage = Storage.new auto_close: false
 
     examine_context : ExamineContext = {
-      file_count: 0,
+      file_counter:              (YieldCounter.new 1000),
       cached_contents_signature: {} of String => String,
-      deleted_title_ids: [] of String,
-      deleted_entry_ids: [] of String
+      deleted_title_ids:         [] of String,
+      deleted_entry_ids:         [] of String,
     }
 
     @title_ids.select! do |title_id|

src/library/title.cr

@@ -115,7 +115,7 @@ class Title
     previous_entries_size = @entries.size
     @entries.select! do |entry|
       existence = File.exists? entry.zip_path
-      yield_process_file context
+      context["file_counter"].count_and_yield
       context["deleted_entry_ids"] << entry.id unless existence
       existence
     end

src/library/types.cr

@@ -134,14 +134,21 @@ class TitleInfo
   end
 end
 
+class YieldCounter
+  setter threshold : Int32
+
+  def initialize(@threshold : Int32)
+    @file_count = 0
+  end
+
+  def count_and_yield
+    @file_count += 1
+    Fiber.yield if @file_count % @threshold == 0
+  end
+end
+
 alias ExamineContext = NamedTuple(
-  file_count: Int32,
+  file_counter: YieldCounter,
   cached_contents_signature: Hash(String, String),
   deleted_title_ids: Array(String),
-  deleted_entry_ids: Array(String)
-)
-
-def yield_process_file(context : ExamineContext)
-  context["file_count"] += 1
-  Fiber.yield if context["file_count"] % 1000 == 0
-end
+  deleted_entry_ids: Array(String))