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diff --git a/jni/ruby/lib/sync.rb b/jni/ruby/lib/sync.rb
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+#
+#   sync.rb - 2 phase lock with counter
+#       $Release Version: 1.0$
+#       $Revision: 40825 $
+#       by Keiju ISHITSUKA(keiju@ishitsuka.com)
+#
+# --
+#  Sync_m, Synchronizer_m
+#  Usage:
+#   obj.extend(Sync_m)
+#   or
+#   class Foo
+#       include Sync_m
+#       :
+#   end
+#
+#   Sync_m#sync_mode
+#   Sync_m#sync_locked?, locked?
+#   Sync_m#sync_shared?, shared?
+#   Sync_m#sync_exclusive?, sync_exclusive?
+#   Sync_m#sync_try_lock, try_lock
+#   Sync_m#sync_lock, lock
+#   Sync_m#sync_unlock, unlock
+#
+#  Sync, Synchronizer:
+#  Usage:
+#   sync = Sync.new
+#
+#   Sync#mode
+#   Sync#locked?
+#   Sync#shared?
+#   Sync#exclusive?
+#   Sync#try_lock(mode) -- mode = :EX, :SH, :UN
+#   Sync#lock(mode)     -- mode = :EX, :SH, :UN
+#   Sync#unlock
+#   Sync#synchronize(mode) {...}
+#
+#
+
+unless defined? Thread
+  raise "Thread not available for this ruby interpreter"
+end
+
+##
+# A module that provides a two-phase lock with a counter.
+
+module Sync_m
+  # lock mode
+  UN = :UN
+  SH = :SH
+  EX = :EX
+
+  # exceptions
+  class Err < StandardError
+    def Err.Fail(*opt)
+      fail self, sprintf(self::Message, *opt)
+    end
+
+    class UnknownLocker < Err
+      Message = "Thread(%s) not locked."
+      def UnknownLocker.Fail(th)
+        super(th.inspect)
+      end
+    end
+
+    class LockModeFailer < Err
+      Message = "Unknown lock mode(%s)"
+      def LockModeFailer.Fail(mode)
+        if mode.id2name
+          mode = id2name
+        end
+        super(mode)
+      end
+    end
+  end
+
+  def Sync_m.define_aliases(cl)
+    cl.module_eval %q{
+      alias locked? sync_locked?
+      alias shared? sync_shared?
+      alias exclusive? sync_exclusive?
+      alias lock sync_lock
+      alias unlock sync_unlock
+      alias try_lock sync_try_lock
+      alias synchronize sync_synchronize
+    }
+  end
+
+  def Sync_m.append_features(cl)
+    super
+    # do nothing for Modules
+    # make aliases for Classes.
+    define_aliases(cl) unless cl.instance_of?(Module)
+    self
+  end
+
+  def Sync_m.extend_object(obj)
+    super
+    obj.sync_extend
+  end
+
+  def sync_extend
+    unless (defined? locked? and
+            defined? shared? and
+            defined? exclusive? and
+            defined? lock and
+            defined? unlock and
+            defined? try_lock and
+            defined? synchronize)
+      Sync_m.define_aliases(singleton_class)
+    end
+    sync_initialize
+  end
+
+  # accessing
+  def sync_locked?
+    sync_mode != UN
+  end
+
+  def sync_shared?
+    sync_mode == SH
+  end
+
+  def sync_exclusive?
+    sync_mode == EX
+  end
+
+  # locking methods.
+  def sync_try_lock(mode = EX)
+    return unlock if mode == UN
+    @sync_mutex.synchronize do
+      sync_try_lock_sub(mode)
+    end
+  end
+
+  def sync_lock(m = EX)
+    return unlock if m == UN
+    Thread.handle_interrupt(StandardError => :on_blocking) do
+      while true
+        @sync_mutex.synchronize do
+          begin
+            if sync_try_lock_sub(m)
+              return self
+            else
+              if sync_sh_locker[Thread.current]
+                sync_upgrade_waiting.push [Thread.current, sync_sh_locker[Thread.current]]
+                sync_sh_locker.delete(Thread.current)
+              else
+                unless sync_waiting.include?(Thread.current) || sync_upgrade_waiting.reverse_each.any?{|w| w.first == Thread.current }
+                  sync_waiting.push Thread.current
+                end
+              end
+              @sync_mutex.sleep
+            end
+          ensure
+            sync_waiting.delete(Thread.current)
+          end
+        end
+      end
+    end
+    self
+  end
+
+  def sync_unlock(m = EX)
+    wakeup_threads = []
+    @sync_mutex.synchronize do
+      if sync_mode == UN
+        Err::UnknownLocker.Fail(Thread.current)
+      end
+
+      m = sync_mode if m == EX and sync_mode == SH
+
+      runnable = false
+      case m
+      when UN
+        Err::UnknownLocker.Fail(Thread.current)
+
+      when EX
+        if sync_ex_locker == Thread.current
+          if (self.sync_ex_count = sync_ex_count - 1) == 0
+            self.sync_ex_locker = nil
+            if sync_sh_locker.include?(Thread.current)
+              self.sync_mode = SH
+            else
+              self.sync_mode = UN
+            end
+            runnable = true
+          end
+        else
+          Err::UnknownLocker.Fail(Thread.current)
+        end
+
+      when SH
+        if (count = sync_sh_locker[Thread.current]).nil?
+          Err::UnknownLocker.Fail(Thread.current)
+        else
+          if (sync_sh_locker[Thread.current] = count - 1) == 0
+            sync_sh_locker.delete(Thread.current)
+            if sync_sh_locker.empty? and sync_ex_count == 0
+              self.sync_mode = UN
+              runnable = true
+            end
+          end
+        end
+      end
+
+      if runnable
+        if sync_upgrade_waiting.size > 0
+          th, count = sync_upgrade_waiting.shift
+          sync_sh_locker[th] = count
+          th.wakeup
+          wakeup_threads.push th
+        else
+          wait = sync_waiting
+          self.sync_waiting = []
+          for th in wait
+            th.wakeup
+            wakeup_threads.push th
+          end
+        end
+      end
+    end
+    for th in wakeup_threads
+      th.run
+    end
+    self
+  end
+
+  def sync_synchronize(mode = EX)
+    Thread.handle_interrupt(StandardError => :on_blocking) do
+      sync_lock(mode)
+      begin
+        yield
+      ensure
+        sync_unlock
+      end
+    end
+  end
+
+  attr_accessor :sync_mode
+
+  attr_accessor :sync_waiting
+  attr_accessor :sync_upgrade_waiting
+  attr_accessor :sync_sh_locker
+  attr_accessor :sync_ex_locker
+  attr_accessor :sync_ex_count
+
+  def sync_inspect
+    sync_iv = instance_variables.select{|iv| /^@sync_/ =~ iv.id2name}.collect{|iv| iv.id2name + '=' + instance_eval(iv.id2name).inspect}.join(",")
+    print "<#{self.class}.extend Sync_m: #{inspect}, <Sync_m: #{sync_iv}>"
+  end
+
+  private
+
+  def sync_initialize
+    @sync_mode = UN
+    @sync_waiting = []
+    @sync_upgrade_waiting = []
+    @sync_sh_locker = Hash.new
+    @sync_ex_locker = nil
+    @sync_ex_count = 0
+
+    @sync_mutex = Mutex.new
+  end
+
+  def initialize(*args)
+    super
+    sync_initialize
+  end
+
+  def sync_try_lock_sub(m)
+    case m
+    when SH
+      case sync_mode
+      when UN
+        self.sync_mode = m
+        sync_sh_locker[Thread.current] = 1
+        ret = true
+      when SH
+        count = 0 unless count = sync_sh_locker[Thread.current]
+        sync_sh_locker[Thread.current] = count + 1
+        ret = true
+      when EX
+        # in EX mode, lock will upgrade to EX lock
+        if sync_ex_locker == Thread.current
+          self.sync_ex_count = sync_ex_count + 1
+          ret = true
+        else
+          ret = false
+        end
+      end
+    when EX
+      if sync_mode == UN or
+          sync_mode == SH && sync_sh_locker.size == 1 && sync_sh_locker.include?(Thread.current)
+        self.sync_mode = m
+        self.sync_ex_locker = Thread.current
+        self.sync_ex_count = 1
+        ret = true
+      elsif sync_mode == EX && sync_ex_locker == Thread.current
+        self.sync_ex_count = sync_ex_count + 1
+        ret = true
+      else
+        ret = false
+      end
+    else
+      Err::LockModeFailer.Fail mode
+    end
+    return ret
+  end
+end
+
+##
+# An alias for Sync_m from sync.rb
+
+Synchronizer_m = Sync_m
+
+##
+# A class that provides two-phase lock with a counter.  See Sync_m for
+# details.
+
+class Sync
+  include Sync_m
+end
+
+##
+# An alias for Sync from sync.rb.  See Sync_m for details.
+
+Synchronizer = Sync