added RingBuffer#peek

Author: mighe

lib/concurrent/channel/ring_buffer.rb

@@ -47,6 +47,10 @@ def take
       end
     end
 
+    def peek
+      @mutex.synchronize { @buffer[@first] }
+    end
+
     private
 
     def wait_while_full

spec/concurrent/channel/ring_buffer_spec.rb

@@ -5,7 +5,7 @@ module Concurrent
   describe RingBuffer do
 
     let(:capacity) { 3 }
-    let(:buffer) { RingBuffer.new( capacity ) }
+    let(:buffer) { RingBuffer.new(capacity) }
 
     def fill_buffer
       capacity.times { buffer.put 3 }
@@ -111,6 +111,28 @@ def fill_buffer
       end
     end
 
+    describe '#peek' do
+      context 'buffer empty' do
+        it 'returns nil when buffer is empty' do
+          buffer.peek.should be_nil
+        end
+      end
+
+      context 'not empty' do
+
+        before(:each) { buffer.put 'element' }
+
+        it 'returns the first value' do
+          buffer.peek.should eq 'element'
+        end
+
+        it 'does not change buffer' do
+          buffer.peek
+          buffer.count.should eq 1
+        end
+      end
+    end
+
     context 'circular condition' do
       it 'can filled many times' do
         fill_buffer