added circular condition

Author: mighe

lib/concurrent/channel/ring_buffer.rb

@@ -21,7 +21,7 @@ def put(value)
       @mutex.synchronize do
         wait_while_full
         @buffer[@last] = value
-        @last += 1
+        @last = (@last + 1) % @buffer.size
         @count += 1
         @condition.signal
       end
@@ -32,7 +32,7 @@ def take
         wait_while_empty
         result = @buffer[@first]
         @buffer[@first] = nil
-        @first += 1
+        @first = (@first + 1) % @buffer.size
         @count -= 1
         @condition.signal
         result

spec/concurrent/channel/ring_buffer_spec.rb

@@ -85,5 +85,17 @@ module Concurrent
       end
     end
 
+    context 'circular condition' do
+      it 'can filled many times' do
+        capacity.times { buffer.put 3 }
+        capacity.times { buffer.take }
+
+        buffer.put 'hi'
+
+        buffer.take.should eq 'hi'
+        buffer.capacity.should eq capacity
+      end
+    end
+
   end
 end