Added call get to RemainingCapacity for a Sequencer

- mirror java 6319789fd4690ad2e1dc54741f56ed1d600c2a82

Author: damageboy

Diff for: Disruptor.Tests/SequencerTests.cs

@@ -173,6 +173,18 @@ public void ShouldRejectAvailableCapcityLessThanOne()
             _sequencer.TryNext(0);
         }
 
+        [Test]
+        public void ShouldCalculateRemainingCapacity()
+        {
+            Assert.AreEqual(4L, _sequencer.RemainingCapacity());
+            _sequencer.Publish(_sequencer.Next());
+            Assert.AreEqual(3L, _sequencer.RemainingCapacity());
+            _sequencer.Publish(_sequencer.Next());
+            Assert.AreEqual(2L, _sequencer.RemainingCapacity());
+            _sequencer.Publish(_sequencer.Next());
+            Assert.AreEqual(1L, _sequencer.RemainingCapacity());
+        }
+
         private void FillBuffer()
         {
             for (int i = 0; i < BufferSize; i++)

Diff for: Disruptor/Sequencer.cs

@@ -198,5 +198,12 @@ private void Publish(long sequence, int batchSize)
             _claimStrategy.SerialisePublishing(sequence, _cursor, batchSize);
             _waitStrategy.SignalAllWhenBlocking();
         }
+
+        public long RemainingCapacity()
+        {
+            long consumed = Util.GetMinimumSequence(_gatingSequences);
+            long produced = _cursor.Value;
+            return BufferSize - (produced - consumed);
+        }
     }
 }