Added the code for a thread-safe data structure

blocking_queue/complete.rb

@@ -0,0 +1,26 @@
+require "thread"
+
+class BlockingQueue
+  def initialize
+    @storage = Array.new
+    @mutex = Mutex.new
+    @condvar = ConditionalVariable.new
+  end
+
+  def push(item)
+    @mutex.synchronize do
+      @storage.push(item)
+      @condvar.signal
+    end
+  end
+
+  def pop
+    @mutex.synchronize do
+      while @storage.empty?
+        @condvar.wait(@mutex)
+      end
+
+      @storage.shift
+    end
+  end
+end

blocking_queue/pre_condvar.rb

@@ -0,0 +1,20 @@
+require "thread"
+
+class BlockingQueue
+  def initialize
+    @storage = Array.new
+    @mutex = Mutex.new
+  end
+
+  def push(item)
+    @mutex.synchronize do
+      @storage.push(item)
+    end
+  end
+
+  def pop
+    @mutex.synchronize do
+      @storage.shift
+    end
+  end
+end

blocking_queue/pre_mutex.rb

@@ -0,0 +1,13 @@
+class BlockingQueue
+  def initialize
+    @storage = Array.new
+  end
+
+  def push(item)
+    @storage.push(item)
+  end
+
+  def pop
+    @storage.shift
+  end
+end