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...)

1 files changed, 4 insertions, 3 deletions

diff --git a/csharp/src/ProtocolBuffers/CodedInputStream.cs b/csharp/src/ProtocolBuffers/CodedInputStream.cs
index 17fcc64b..447adbb1 100644
--- a/csharp/src/ProtocolBuffers/CodedInputStream.cs
+++ b/csharp/src/ProtocolBuffers/CodedInputStream.cs
@@ -38,6 +38,7 @@ using System;
 using System.Collections.Generic;

 using System.IO;

 using System.Text;

+using Google.Protobuf.Collections;

 using Google.Protobuf.Descriptors;

 

 namespace Google.Protobuf

@@ -700,7 +701,7 @@ namespace Google.Protobuf
             }

         }

 

-        public void ReadEnumArray<T>(uint fieldTag, ICollection<T> list)

+        public void ReadEnumArray<T>(uint fieldTag, RepeatedField<T> list)

             where T : struct, IComparable, IFormattable

         {

             WireFormat.WireType wformat = WireFormat.GetTagWireType(fieldTag);

@@ -712,8 +713,8 @@ namespace Google.Protobuf
                 int limit = PushLimit(length);

                 while (!ReachedLimit)

                 {

-                    // TODO(jonskeet): Avoid this horrible boxing!

-                    list.Add((T)(object) ReadEnum());

+                    // Ghastly hack, but it works...

+                    list.AddInt32(ReadEnum());

                 }

                 PopLimit(limit);

             }