Fix Issue 344 by resolving infinite loop with buffers longer than Max…

…ArrayLength.

UnitTests/Tests.cs

@@ -4057,7 +4057,25 @@ protected override void TestDroppingLargeBuffer(long maxFreeLargeBufferSize)
                 }
             }
         }
+#pragma warning disable 618 // Timeout is obsolete because it kills the thread, which isn't allowed, but it's still handy
+                            // for tests that are expected to run indefinitely in the failure case.
+        [Test, Timeout(10000)]
+        public void TryGetBuffer_InfiniteLoop_Issue344()
+        {
+            // see https://github.com/microsoft/Microsoft.IO.RecyclableMemoryStream/issues/344
+            var memMgr = this.GetMemoryManager();
+            var size = 1073741825; // this will cause infinite loop in TryGetBuffer below, 1073741824 works.
+            var bytes = new byte[size];
+            using (var ms = memMgr.GetStream())
+            {
+                ms.Write(bytes, 0, size);
+                bool result = ms.TryGetBuffer(out var segment);
+                Assert.That(result, Is.False);
+                Assert.That(segment, Is.Empty);
+            }
+        }
     }
+#pragma warning restore 618
 
     [TestFixture]
     public sealed class RecyclableMemoryStreamTestsWithPassiveBufferReleaseUsingExponentialLargeBuffer : BaseRecyclableMemoryStreamTestsUsingExponentialLargeBuffer

src/RecyclableMemoryStream.cs

@@ -494,6 +494,7 @@ public override long Position
         /// until <see cref="Dispose(bool)"/> is called, but the next time <c>GetBuffer</c> is called, a new buffer from the pool will be required.</remarks>
         /// <exception cref="ObjectDisposedException">Object has been disposed.</exception>
         /// <exception cref="OutOfMemoryException">stream is too large for a contiguous buffer.</exception>
+        /// <exception cref="OverflowException">stream is too long for a contiguous buffer.</exception>
         public override byte[] GetBuffer()
         {
             this.CheckDisposed();

src/RecyclableMemoryStreamManager.cs

@@ -378,13 +378,13 @@ internal byte[] GetBlock()
         /// <exception cref="OutOfMemoryException">Requested array size is larger than the maximum allowed.</exception>
         internal byte[] GetLargeBuffer(long requiredSize, Guid id, string? tag)
         {
+            requiredSize = this.RoundToLargeBufferSize(requiredSize);
+
             if (requiredSize > MaxArrayLength)
             {
-                throw new OutOfMemoryException($"Requested size exceeds maximum array length of {MaxArrayLength}.");
+                throw new OutOfMemoryException($"Required buffer size exceeds maximum array length of {MaxArrayLength}.");
             }
 
-            requiredSize = this.RoundToLargeBufferSize(requiredSize);
-
             var poolIndex = this.GetPoolIndex(requiredSize);
 
             bool createdNew = false;