Add an LRU cache

lib/phlex.rb

@@ -14,6 +14,7 @@ module Phlex
 	autoload :Unbuffered, "phlex/unbuffered"
 	autoload :ConcurrentMap, "phlex/concurrent_map"
 	autoload :BlackHole, "phlex/black_hole"
+	autoload :LRU, "phlex/lru"
 
 	# Included in all Phlex exceptions allowing you to match any Phlex error.
 	# @example Rescue any Phlex error:

lib/phlex/lru.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+class Phlex::LRU
+	def initialize(max_byte_size)
+		@hash = {}
+		@mutex = Mutex.new
+
+		@size = 0
+		@max_byte_size = max_byte_size
+	end
+
+	def [](key)
+		@mutex.synchronize do
+			if (value = @hash[key])
+				@hash.delete(key)
+				@hash[key] = value
+			end
+		end
+	end
+
+	def []=(key, value)
+		@mutex.synchronize do
+			old_value = @hash.delete(key)
+			@hash[key] = value
+
+			@size += value.bytesize - (old_value ? old_value.bytesize : 0)
+
+			while @size > @max_byte_size
+				key, value = @hash.shift
+				@size -= value.bytesize
+			end
+		end
+	end
+
+	def delete(key)
+		@mutex.synchronize do
+			old_value = @hash.delete(key)
+			@size -= old_value.bytesize if old_value
+		end
+	end
+
+	def include?(key)
+		@hash.include?(key)
+	end
+
+	def fetch(key)
+		@mutex.synchronize do
+			if (value = @hash[key])
+				value
+			else
+				@hash[key] = yield
+			end
+		end
+	end
+
+	def size
+		@hash.size
+	end
+
+	def empty?
+		@hash.empty?
+	end
+
+	def clear
+		@mutex.synchronize do
+			@hash.clear
+		end
+	end
+end