Add config 'forcely_yield_count'

the default value 1000 would make a fiber yield on each 4ms on SSD

Apply yield counter in Dir.contents_signauture
Use contents_signature cache in Title.new

src/config.cr

@@ -23,6 +23,7 @@ class Config
   property cache_enabled = false
   property cache_size_mbs = 50
   property cache_log_enabled = true
+  property forcely_yield_count = 1000
   property disable_login = false
   property default_username = ""
   property auth_proxy_header_name = ""

src/library/library.cr

@@ -133,8 +133,9 @@ class Library
 
     storage = Storage.new auto_close: false
 
+    count = Config.current.forcely_yield_count
     examine_context : ExamineContext = {
-      file_counter:              (YieldCounter.new 1000),
+      file_counter:              (YieldCounter.new count),
       cached_contents_signature: {} of String => String,
       deleted_title_ids:         [] of String,
       deleted_entry_ids:         [] of String,

src/library/title.cr

@@ -19,7 +19,7 @@ class Title
   @[YAML::Field(ignore: true)]
   @cached_cover_url : String?
 
-  def initialize(@dir : String, @parent_id, cache : Hash(String, String)? = nil)
+  def initialize(@dir : String, @parent_id, cache = {} of String => String)
     storage = Storage.default
     @signature = Dir.signature dir
     id = storage.get_title_id dir, signature
@@ -43,7 +43,7 @@ class Title
       next if fn.starts_with? "."
       path = File.join dir, fn
       if File.directory? path
-        title = Title.new path, @id
+        title = Title.new path, @id, cache
         next if title.entries.size == 0 && title.titles.size == 0
         Library.default.title_hash[title.id] = title
         @title_ids << title.id
@@ -73,7 +73,7 @@ class Title
   def examine(context : ExamineContext) : Bool
     return false unless Dir.exists? @dir # No title, Remove this
     contents_signature = Dir.contents_signature @dir,
-      context["cached_contents_signature"]
+      context["cached_contents_signature"], context["file_counter"]
     # Not changed. Reuse this
     return true if @contents_signature == contents_signature
 

src/util/signature.cr

@@ -54,9 +54,11 @@ class Dir
   # Rescan conditions:
   #   - When a file added, moved, removed, renamed (including which in nested
   #       directories)
-  def self.contents_signature(dirname, cache = {} of String => String) : String
+  def self.contents_signature(dirname,
-    return cache[dirname] if !cache.nil? && cache[dirname]?
+                              cache = {} of String => String,
-    Fiber.yield # Yield first
+                              counter : YieldCounter? = nil) : String
+    return cache[dirname] if cache[dirname]?
+    counter.count_and_yield unless counter.nil?
     signatures = [] of String
     self.open dirname do |dir|
       dir.entries.sort.each do |fn|
@@ -69,10 +71,11 @@ class Dir
           #   supported file
           signatures << fn if is_supported_file fn
         end
+        counter.count_and_yield unless counter.nil?
       end
     end
     hash = Digest::SHA1.hexdigest(signatures.join)
-    cache[dirname] = hash unless cache.nil?
+    cache[dirname] = hash
     hash
   end
 end