From: David Nissimoff <davidni@microsoft.com>
Date: Sat, 18 Nov 2017 15:11:06 +0000 (-0800)
Subject: Fix #15057 MemoryStream.CopyToAsync calls Write / WriteAsync with count=0 (#15070)
X-Git-Tag: accepted/tizen/base/20180629.140029~539
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=02e499eb04d42d35943ce7a78f078c8a16aedb3f;p=platform%2Fupstream%2Fcoreclr.git

Fix #15057 MemoryStream.CopyToAsync calls Write / WriteAsync with count=0 (#15070)
---

diff --git a/src/mscorlib/src/System/IO/MemoryStream.cs b/src/mscorlib/src/System/IO/MemoryStream.cs
index d2fd83d..6039dc7 100644
--- a/src/mscorlib/src/System/IO/MemoryStream.cs
+++ b/src/mscorlib/src/System/IO/MemoryStream.cs
@@ -541,6 +541,10 @@ namespace System.IO
             Int32 pos = _position;
             Int32 n = InternalEmulateRead(_length - _position);
 
+            // If we were already at or past the end, there's no copying to do so just quit.
+            if (n == 0)
+                return Task.CompletedTask;
+
             // If destination is not a memory stream, write there asynchronously:
             MemoryStream memStrDest = destination as MemoryStream;
             if (memStrDest == null)