MVar: non-blocking variants.

Author: chrisseaton

lib/concurrent/mvar.rb

@@ -66,6 +66,53 @@ def modify(timeout = nil)
       end
     end
 
+    def try_take!
+      @mutex.synchronize do
+        if full?
+          value = @value
+          @value = EMPTY
+          @empty_condition.signal
+          value
+        else
+          EMPTY
+        end
+      end
+    end
+
+    def try_put!(value)
+      @mutex.synchronize do
+        if empty?
+          @value = value
+          @full_condition.signal
+          true
+        else
+          false
+        end
+      end
+    end
+
+    def set!(value)
+      @mutex.synchronize do
+        @value = value
+        @full_condition.signal
+      end
+    end
+
+    def modify!(timeout = nil)
+      raise ArgumentError.new('no block given') unless block_given?
+
+      @mutex.synchronize do
+        value = @value
+        @value = yield value
+        if @value == EMPTY
+          @empty_condition.signal
+        else
+          @full_condition.signal
+        end
+        value
+      end
+    end
+
     def empty?
       @value == EMPTY
     end

spec/concurrent/mvar_spec.rb

@@ -178,6 +178,101 @@ module Concurrent
 
     end
 
+    context '#try_put!' do
+
+      it 'returns true an empty MVar' do
+        m = MVar.new
+        m.try_put!(14).should eq true
+      end
+
+      it 'returns false on a full MVar' do
+        m = MVar.new(14)
+        m.try_put!(14).should eq false
+      end
+
+      it 'sets an empty MVar to be full' do
+        m = MVar.new
+        m.try_put! 14
+        m.should be_full
+      end
+
+    end
+
+    context '#try_take!' do
+
+      it 'returns EMPTY an empty MVar' do
+        m = MVar.new
+        m.try_take!.should eq MVar::EMPTY
+      end
+
+      it 'returns the value on a full MVar' do
+        m = MVar.new(14)
+        m.try_take!.should eq 14
+      end
+
+      it 'sets a full MVar to be empty' do
+        m = MVar.new(14)
+        m.try_take!
+        m.should be_empty
+      end
+
+    end
+
+    context '#set!' do
+
+      it 'sets an empty MVar to be full' do
+        m = MVar.new
+        m.set! 14
+        m.should be_full
+      end
+
+      it 'sets a full MVar to be full' do
+        m = MVar.new(2)
+        m.set! 14
+        m.should be_full
+        m.take.should eq 14
+      end
+
+    end
+
+    context '#modify!' do
+
+      it 'raises an exception when no block given' do
+        m = MVar.new(14)
+        expect { m.modify! }.to raise_error(ArgumentError)
+      end
+
+      it 'modifies a full MVar' do
+        m = MVar.new(14)
+        m.modify!{ |v| v + 2 }
+        m.take.should eq 16
+      end
+
+      it 'modifies an empty MVar' do
+        m = MVar.new
+        m.modify!{ |v| 14 }
+        m.take.should eq 14
+      end
+
+      it 'can be used to set a full MVar to empty' do
+        m = MVar.new(14)
+        m.modify!{ |v| MVar::EMPTY }
+        m.should be_empty
+      end
+
+      it 'can be used to set an empty MVar to empty' do
+        m = MVar.new
+        m.modify!{ |v| MVar::EMPTY }
+        m.should be_empty
+      end
+
+      it 'returns the unmodified value' do
+        m = MVar.new(14)
+        m.modify!{ |v| v + 2 }.should eq 14
+      end
+
+    end
+
   end
 
 end