From db10ffc9e9fa0c67d92a3f7f2b73894ee97fa8e3 Mon Sep 17 00:00:00 2001
From: Daniel Marbach <daniel.marbach@openplace.net>
Date: Thu, 25 Mar 2021 23:46:55 +0100
Subject: [PATCH] ReadStreamToArraySegment use BufferListStream directly when
 available (#19823)

---
 .../src/Amqp/AmqpMessageConverter.cs              | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/sdk/servicebus/Azure.Messaging.ServiceBus/src/Amqp/AmqpMessageConverter.cs b/sdk/servicebus/Azure.Messaging.ServiceBus/src/Amqp/AmqpMessageConverter.cs
index 3f0a6b7e9f4d0..fb78f6847b87e 100644
--- a/sdk/servicebus/Azure.Messaging.ServiceBus/src/Amqp/AmqpMessageConverter.cs
+++ b/sdk/servicebus/Azure.Messaging.ServiceBus/src/Amqp/AmqpMessageConverter.cs
@@ -139,10 +139,17 @@ private static ArraySegment<byte> ReadStreamToArraySegment(Stream stream)
                 return new ArraySegment<byte>();
             }
 
-            using var memStream = new MemoryStream(StreamBufferSizeInBytes);
-            stream.CopyTo(memStream, StreamBufferSizeInBytes);
-
-            return new ArraySegment<byte>(memStream.ToArray());
+            switch (stream)
+            {
+                case BufferListStream bufferListStream:
+                    return bufferListStream.ReadBytes((int)stream.Length);
+                default:
+                {
+                    using var memStream = new MemoryStream(StreamBufferSizeInBytes);
+                    stream.CopyTo(memStream, StreamBufferSizeInBytes);
+                    return new ArraySegment<byte>(memStream.ToArray());
+                }
+            }
         }
 
         public static AmqpMessage SBMessageToAmqpMessage(SBMessage sbMessage)