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diff --git a/lib/mahoro/thread_safe.rb b/lib/mahoro/thread_safe.rb
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+require 'thread'
+
+# Adds thread-safety to an existing Mahoro object.
+#
+# magic_t cookies of libmagic are not thread-safe by default,
+# thus Mahoro is not thread-safe by default, either.
+#
+# For applications using persistent thread pools, this module is NOT
+# recommended.  Instead, it is best to create thread-local instances
+# of (non-thread-safe) Mahoro for best performance.
+#
+# This is only intended for applications using Mahoro which meet the
+# following requirements:
+# 1) uses short-lived threads
+# 2) does not need high concurrency for Mahoro operations
+#
+# Usage example:
+#     require "mahoro/thread_safe"
+#
+#     # create a Mahoro object as usual
+#     mahoro_obj = Mahoro.new(...)
+#
+#     # enable thread-safety
+#     mahoro_obj.extend Mahoro::ThreadSafe
+#
+#     # mahoro_obj may now be used by multiple threads with automatic
+#     # mutual exclusion (the following example is safe, but not concurrent).
+#     Thread.new { mahoro_obj.file("/path/to/some_file") }
+#     Thread.new { mahoro_obj.file("/path/to/some_other_file") }
+#
+#     # Real concurrency must be achieved by using different Mahoro objects
+#     # in different threads.  As of Mahoro v0.4, Mahoro releases the GVL
+#     # on (Matz) Ruby 1.9 and later.
+module Mahoro::ThreadSafe
+
+  def self.extended(obj) # :nodoc:
+    obj.instance_variable_set(:@lock, Mutex.new)
+  end
+
+  eval(
+    %w(file buffer flags= valid? compile load).map do |meth|
+      "\ndef #{meth}(*args)\n  @lock.synchronize { super }\nend\n"
+    end.join("")
+  )
+end