MVar: include Dereferenceable.

Author: chrisseaton

lib/concurrent/dereferenceable.rb

@@ -32,19 +32,23 @@ def set_deref_options(opts = {})
     # by the #set_deref_options method.
     def value
       mutex.synchronize do
-        return nil if @value.nil?
-        return @value if @do_nothing_on_deref
-        value = @value
-        value = @copy_on_deref.call(value) if @copy_on_deref
-        value = value.dup if @dup_on_deref
-        value = value.freeze if @freeze_on_deref
-        value
+        apply_deref_options(@value)
       end
     end
     alias_method :deref, :value
 
     protected
 
+    def apply_deref_options(value)
+      return nil if value.nil?
+      return value if @do_nothing_on_deref
+      value = value
+      value = @copy_on_deref.call(value) if @copy_on_deref
+      value = value.dup if @dup_on_deref
+      value = value.freeze if @freeze_on_deref
+      value
+    end
+
     def mutex # :nodoc:
       @mutex
     end

lib/concurrent/mvar.rb

@@ -4,14 +4,17 @@ module Concurrent
 
   class MVar
 
+    include Dereferenceable
+
     EMPTY = Object.new
     TIMEOUT = Object.new
 
-    def initialize(value=EMPTY)
+    def initialize(value = EMPTY, opts = {})
       @value = value
       @mutex = Mutex.new
       @empty_condition = ConditionVariable.new
       @full_condition = ConditionVariable.new
+      set_deref_options(opts)
     end
 
     def take(timeout = nil)
@@ -24,7 +27,7 @@ def take(timeout = nil)
           value = @value
           @value = EMPTY
           @empty_condition.signal
-          value
+          apply_deref_options(value)
         else
           TIMEOUT
         end
@@ -40,7 +43,7 @@ def put(value, timeout = nil)
         if empty?
           @value = value
           @full_condition.signal
-          value
+          apply_deref_options(value)
         else
           TIMEOUT
         end
@@ -59,7 +62,7 @@ def modify(timeout = nil)
           value = @value
           @value = yield value
           @full_condition.signal
-          value
+          apply_deref_options(value)
         else
           TIMEOUT
         end
@@ -72,7 +75,7 @@ def try_take!
           value = @value
           @value = EMPTY
           @empty_condition.signal
-          value
+          apply_deref_options(value)
         else
           EMPTY
         end
@@ -93,8 +96,10 @@ def try_put!(value)
 
     def set!(value)
       @mutex.synchronize do
+        old_value = @value
         @value = value
         @full_condition.signal
+        apply_deref_options(old_value)
       end
     end
 
@@ -109,7 +114,7 @@ def modify!(timeout = nil)
         else
           @full_condition.signal
         end
-        value
+        apply_deref_options(value)
       end
     end
 

md/mvar.md

@@ -10,12 +10,17 @@ On top of the fundamental `#put` and `#take` operations, we also provide a
 operations all support timeouts.
 
 We also support non-blocking operations `#try_put!` and `#try_take!`, a `#set!`
-that ignores existing values, and a `#modify!` that yields `MVar::EMPTY` if the
+that ignores existing values, a `#value` that returns the value without removing
+it or returns `MVar::EMPTY`, and a `#modify!` that yields `MVar::EMPTY` if the
 `MVar` is empty and can be used to set `MVar::EMPTY`. You shouldn't use these
 operations in the first instance.
 
-`MVar is related to M-structures in Id, MVar in Haskell and SyncVar in Scala.
-`See
+`MVar` is a Dereferenceable.
+
+`MVar` is related to M-structures in Id, `MVar` in Haskell and `SyncVar` in
+Scala.
+
+See:
 
 1.  P. Barth, R. Nikhil, and Arvind. M-Structures: Extending a parallel, non-
 strict, functional language with state. In Proceedings of the 5th ACM Conference

spec/concurrent/mvar_spec.rb

@@ -4,6 +4,18 @@ module Concurrent
 
   describe MVar do
 
+    context 'behavior' do
+
+      # dereferenceable
+
+      def dereferenceable_subject(value, opts = {})
+        MVar.new(value, opts)
+      end
+
+      it_should_behave_like :dereferenceable
+      
+    end
+
     context '#initialize' do
 
       it 'accepts no initial value' do
@@ -233,6 +245,16 @@ module Concurrent
         m.take.should eq 14
       end
 
+      it 'returns EMPTY on an empty MVar' do
+        m = MVar.new
+        m.set!(2).should eq MVar::EMPTY
+      end
+
+      it 'returns the original value on a full MVar' do
+        m = MVar.new(14)
+        m.set!(2).should eq 14
+      end
+
     end
 
     context '#modify!' do