Reimplement RepeatedField<T> using an array as the backing store.

This is effectively reimplementing List<T>, but with a few advantages:
- We know that an empty repeated field is common, so don't allocate an array until we need to
- With direct access to the array, we can easily convert enum values to int without boxing
- We can relax the restrictions over what happens if the repeated field is modified while iterating, avoiding so much checking

This is somewhat risky, in that reimplementing a building block like this is *always* risky, but hey...
(The performance benefits are significant...)

2 files changed, 7 insertions, 6 deletions

diff --git a/csharp/src/ProtocolBuffers.Test/CodedInputStreamTest.cs b/csharp/src/ProtocolBuffers.Test/CodedInputStreamTest.cs
index 450662a6..07f54e94 100644
--- a/csharp/src/ProtocolBuffers.Test/CodedInputStreamTest.cs
+++ b/csharp/src/ProtocolBuffers.Test/CodedInputStreamTest.cs
@@ -487,7 +487,7 @@ namespace Google.Protobuf
             uint tag;

             Assert.IsTrue(input.ReadTag(out tag));

 

-            List<TestNegEnum> values = new List<TestNegEnum>();

+            RepeatedField<TestNegEnum> values = new RepeatedField<TestNegEnum>();

             input.ReadEnumArray(tag, values);

 

             Assert.AreEqual(6, values.Count);

@@ -511,7 +511,7 @@ namespace Google.Protobuf
             uint tag;

             Assert.IsTrue(input.ReadTag(out tag));

 

-            List<TestNegEnum> values = new List<TestNegEnum>();

+            RepeatedField<TestNegEnum> values = new RepeatedField<TestNegEnum>();

             input.ReadEnumArray(tag, values);

 

             Assert.AreEqual(6, values.Count);

diff --git a/csharp/src/ProtocolBuffers.Test/RepeatedFieldTest.cs b/csharp/src/ProtocolBuffers.Test/RepeatedFieldTest.cs
index 94e30189..cbe79294 100644
--- a/csharp/src/ProtocolBuffers.Test/RepeatedFieldTest.cs
+++ b/csharp/src/ProtocolBuffers.Test/RepeatedFieldTest.cs
@@ -40,11 +40,12 @@ namespace Google.Protobuf
         [Test]
         public void Add_RepeatedField()
         {
-            var list = new RepeatedField<string>();
+            var list = new RepeatedField<string> { "original" };
             list.Add(new RepeatedField<string> { "foo", "bar" });
-            Assert.AreEqual(2, list.Count);
-            Assert.AreEqual("foo", list[0]);
-            Assert.AreEqual("bar", list[1]);
+            Assert.AreEqual(3, list.Count);
+            Assert.AreEqual("original", list[0]);
+            Assert.AreEqual("foo", list[1]);
+            Assert.AreEqual("bar", list[2]);
         }
     }
 }