[System.Net.Http] Allow re-sending StreamContent. Fixes #52448

2 files changed, 45 insertions, 3 deletions

diff --git a/mcs/class/System.Net.Http/System.Net.Http/StreamContent.cs b/mcs/class/System.Net.Http/System.Net.Http/StreamContent.cs
index a249aad6f5b..b8c27858a26 100644
--- a/mcs/class/System.Net.Http/System.Net.Http/StreamContent.cs
+++ b/mcs/class/System.Net.Http/System.Net.Http/StreamContent.cs
@@ -37,6 +37,8 @@ namespace System.Net.Http
 		readonly Stream content;
 		readonly int bufferSize;
 		readonly CancellationToken cancellationToken;
+		readonly long startPosition;
+		bool contentCopied;
 
 		public StreamContent (Stream content)
 			: this (content, 16 * 1024)
@@ -53,6 +55,10 @@ namespace System.Net.Http
 
 			this.content = content;
 			this.bufferSize = bufferSize;
+
+			if (content.CanSeek) {
+				startPosition = content.Position;
+			}
 		}
 
 		//
@@ -83,6 +89,16 @@ namespace System.Net.Http
 
 		protected internal override Task SerializeToStreamAsync (Stream stream, TransportContext context)
 		{
+			if (contentCopied) {
+				if (!content.CanSeek) {
+					throw new InvalidOperationException ("The stream was already consumed. It cannot be read again.");
+				}
+
+				content.Seek (startPosition, SeekOrigin.Begin);
+			} else {
+				contentCopied = true;
+			}
+
 			return content.CopyToAsync (stream, bufferSize, cancellationToken);
 		}
 
@@ -92,7 +108,7 @@ namespace System.Net.Http
 				length = 0;
 				return false;
 			}
-			length = content.Length;
+			length = content.Length - startPosition;
 			return true;
 		}
 	}
diff --git a/mcs/class/System.Net.Http/Test/System.Net.Http/StreamContentTest.cs b/mcs/class/System.Net.Http/Test/System.Net.Http/StreamContentTest.cs
index e5609474126..a7c9875186c 100644
--- a/mcs/class/System.Net.Http/Test/System.Net.Http/StreamContentTest.cs
+++ b/mcs/class/System.Net.Http/Test/System.Net.Http/StreamContentTest.cs
@@ -149,8 +149,8 @@ namespace MonoTests.System.Net.Http
 			/*
 			sc = new StreamContent (new ExceptionStream ());
 			try {
-			    sc.CopyToAsync (m).Wait ();
-			    Assert.Fail ("#2");
+				sc.CopyToAsync (m).Wait ();
+				Assert.Fail ("#2");
 			} catch (AggregateException) {
 			}
 			*/ 
@@ -191,6 +191,32 @@ namespace MonoTests.System.Net.Http
 		}
 
 		[Test]
+		public void CopyToAsync_Twice ()
+		{
+			var ms = new MemoryStream();
+			ms.WriteByte(4);
+			ms.WriteByte(12);
+			ms.WriteByte(7);
+			ms.Seek(1, SeekOrigin.Begin);
+
+			var sc = new StreamContent(ms);
+
+			var dest = new MemoryStream();
+			var task = sc.CopyToAsync(dest);
+			Assert.True(task.Wait(3000), "#0");
+			Assert.AreEqual(2, dest.Length, "#1");
+			dest.Seek(0, SeekOrigin.Begin);
+			Assert.AreEqual(12, dest.ReadByte(), "#2");
+
+			dest = new MemoryStream();
+			task = sc.CopyToAsync(dest);
+			Assert.True(task.Wait(3000), "#10");
+			Assert.AreEqual(2, dest.Length, "#11");
+			dest.Seek(0, SeekOrigin.Begin);
+			Assert.AreEqual(12, dest.ReadByte(), "#12");
+		}
+
+		[Test]
 		public void CopyToAsync_ClosedInput ()
 		{
 			var stream = new MemoryStream (new byte[] { 1 });