Merge pull request #52 from AArnott/fix50v2.0.49-alpha

Avoid allocating many small arrays while serializing

2 files changed, 37 insertions, 2 deletions

diff --git a/src/MessagePack/MemoryPoolWithMinSize.cs b/src/MessagePack/MemoryPoolWithMinSize.cs
new file mode 100644
index 00000000..dfe08538
--- /dev/null
+++ b/src/MessagePack/MemoryPoolWithMinSize.cs
@@ -0,0 +1,35 @@
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Text;
+
+namespace MessagePack
+{
+    /// <summary>
+    /// A wrapper around <see cref="MemoryPool{T}.Shared"/> that ensures we never allocate arrays smaller than 4096.
+    /// </summary>
+    internal class MemoryPoolWithMinSize : MemoryPool<byte>
+    {
+        /// <summary>
+        /// The minimum size for an array that we will ever request from the underlying pool.
+        /// </summary>
+        private const int MinSize = 4 * 1024;
+
+        internal static readonly MemoryPoolWithMinSize Instance = new MemoryPoolWithMinSize();
+
+        private MemoryPoolWithMinSize()
+        {
+        }
+
+        /// <inheritdoc />
+        public override int MaxBufferSize => throw new NotImplementedException();
+
+        /// <inheritdoc />
+        public override IMemoryOwner<byte> Rent(int minBufferSize = -1) => Shared.Rent(Math.Max(MinSize, minBufferSize));
+
+        /// <inheritdoc />
+        protected override void Dispose(bool disposing)
+        {
+        }
+    }
+}
diff --git a/src/MessagePack/MessagePackSerializer.cs b/src/MessagePack/MessagePackSerializer.cs
index 637369e4..4a6ec987 100644
--- a/src/MessagePack/MessagePackSerializer.cs
+++ b/src/MessagePack/MessagePackSerializer.cs
@@ -79,7 +79,7 @@ namespace MessagePack
         /// <returns>A byte array with the serialized value.</returns>
         public byte[] Serialize<T>(T value, IFormatterResolver resolver = null)
         {
-            using (var sequence = new Sequence<byte>())
+            using (var sequence = new Sequence<byte>(MemoryPoolWithMinSize.Instance))
             {
                 this.Serialize(sequence, value, resolver);
                 return sequence.AsReadOnlySequence.ToArray();
@@ -94,7 +94,7 @@ namespace MessagePack
         /// <param name="resolver">The resolver to use during deserialization. Use <c>null</c> to use the <see cref="DefaultResolver"/>.</param>
         public void Serialize<T>(Stream stream, T value, IFormatterResolver resolver = null)
         {
-            using (var sequence = new Sequence<byte>())
+            using (var sequence = new Sequence<byte>(MemoryPoolWithMinSize.Instance))
             {
                 this.Serialize<T>(sequence, value, resolver);
                 foreach (var segment in sequence.AsReadOnlySequence)