Add TryGetBuffer, remove buggy bounds check

Remove superfluous bounds checking. Add implementation of TryGetBuffer.

Author: Ben Watson

UnitTests/Tests.cs

@@ -337,7 +337,7 @@ public void GettingBlockAdjustsFreeAndInUseSize()
         }
         #endregion
 
-        #region GetBuffer Tests
+        #region GetBuffer/TryGetBuffer Tests
         [Test]
         public void GetBufferReturnsSingleBlockForBlockSize()
         {
@@ -347,6 +347,7 @@ public void GetBufferReturnsSingleBlockForBlockSize()
             stream.Write(buffer, 0, buffer.Length);
             var returnedBuffer = stream.GetBuffer();
             Assert.That(returnedBuffer.Length, Is.EqualTo(stream.MemoryManager.BlockSize));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -358,6 +359,7 @@ public void GetBufferReturnsSingleBlockForLessThanBlockSize()
             stream.Write(buffer, 0, buffer.Length);
             var returnedBuffer = stream.GetBuffer();
             Assert.That(returnedBuffer.Length, Is.EqualTo(stream.MemoryManager.BlockSize));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -369,6 +371,7 @@ public void GetBufferReturnsLargeBufferForMoreThanBlockSize()
             stream.Write(buffer, 0, buffer.Length);
             var returnedBuffer = stream.GetBuffer();
             Assert.That(returnedBuffer.Length, Is.EqualTo(stream.MemoryManager.LargeBufferMultiple));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -380,6 +383,7 @@ public void GetBufferReturnsSameLarge()
             var returnedBuffer = stream.GetBuffer();
             var returnedBuffer2 = stream.GetBuffer();
             Assert.That(returnedBuffer, Is.SameAs(returnedBuffer2));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -392,6 +396,7 @@ public void GetBufferAdjustsLargePoolFreeSize()
             stream.Write(buffer, 0, buffer.Length);
 
             var newBuffer = stream.GetBuffer();
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
 
             stream.Dispose();
 
@@ -403,6 +408,7 @@ public void GetBufferAdjustsLargePoolFreeSize()
             var newBuffer2 = newStream.GetBuffer();
             Assert.That(newBuffer2.Length, Is.EqualTo(newBuffer.Length));
             Assert.That(memMgr.LargePoolFreeSize, Is.EqualTo(0));
+            RMSAssert.TryGetBufferEqualToGetBuffer(newStream);
         }
 
         [Test]
@@ -422,6 +428,7 @@ public void CallingWriteAfterLargeGetBufferDoesNotLoseData()
             Assert.That(buffer[stream.MemoryManager.BlockSize], Is.EqualTo(13));
             RMSAssert.BuffersAreEqual(buffer, stream.MemoryManager.BlockSize + 1, bytesToWrite, 0, bytesToWrite.Length);
             Assert.That(stream.Position, Is.EqualTo(stream.MemoryManager.BlockSize + 1 + bytesToWrite.Length));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -440,6 +447,7 @@ public void CallingWriteByteAfterLargeGetBufferDoesNotLoseData()
             Assert.That(buffer[stream.MemoryManager.BlockSize], Is.EqualTo(13));
             Assert.That(buffer[stream.MemoryManager.BlockSize + 1], Is.EqualTo(14));
             Assert.That(stream.Position, Is.EqualTo(stream.MemoryManager.BlockSize + 2));
+            RMSAssert.TryGetBufferEqualToGetBuffer(stream);
         }
 
         [Test]
@@ -2312,15 +2320,6 @@ protected virtual bool useExponentialLargeBuffer
             get { return false; }
         }
 
-        /*
-         * TODO: clocke to release logging libraries to enable some tests.
-        [TestFixtureSetUp]
-        public void Setup()
-        {
-            LogManager.Start();
-        }
-        */
-
         protected static class RMSAssert
         {
             /// <summary>
@@ -2371,6 +2370,16 @@ internal static void BuffersAreEqual(byte[] buffer1, int offset1, byte[] buffer2
                 Assert.That(rate, Is.AtMost(tolerance), "Too many errors. Buffers can differ to a tolerance of {0:F4}",
                             tolerance);
             }
+
+            internal static void TryGetBufferEqualToGetBuffer(RecyclableMemoryStream stream)
+            {
+                var buffer = stream.GetBuffer();
+                ArraySegment<byte> segment;
+                Assert.That(stream.TryGetBuffer(out segment), Is.True);
+                Assert.That(segment.Offset, Is.Zero);
+                Assert.That(segment.Count, Is.EqualTo(stream.Length));
+                Assert.That(segment.Array, Is.SameAs(buffer));
+            }
         }
     }
 

src/Microsoft.IO.RecyclableMemoryStream.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard1.4;netstandard2.1;net40;net45;netcoreapp2.1</TargetFrameworks>
+    <TargetFrameworks>netstandard1.4;netstandard2.1;net40;net45;net46;netcoreapp2.1</TargetFrameworks>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
   </PropertyGroup>
   <!-- for assembly signing we use a magic variable coupled with a special build definition which skips UTs -->

src/RecyclableMemoryStream.cs

@@ -452,6 +452,25 @@ public override byte[] GetBuffer()
             return this.largeBuffer;
         }
 
+        /// <summary>
+        /// Returns an ArraySegment that wraps a single buffer containing the contents of the stream.
+        /// </summary>
+        /// <param name="buffer">An ArraySegment containing a reference to the underlying bytes.</param>
+        /// <returns>Always returns true.</returns>
+        /// <remarks>GetBuffer has no failure modes (it always returns something, even if it's an empty buffer), therefore this method
+        /// always returns a valid ArraySegment to the same buffer returned by GetBuffer.</remarks>
+#if NET40 || NET45
+        public bool TryGetBuffer(out ArraySegment<byte> buffer)  
+#else
+        public override bool TryGetBuffer(out ArraySegment<byte> buffer)
+#endif
+        {
+            this.CheckDisposed();
+            buffer = new ArraySegment<byte>(this.GetBuffer(), 0, (int)this.Length);
+            // GetBuffer has no failure modes, so this should always succeed
+            return true;
+        }
+
         /// <summary>
         /// Returns a new array with a copy of the buffer's contents. You should almost certainly be using GetBuffer combined with the Length to 
         /// access the bytes in this stream. Calling ToArray will destroy the benefits of pooled buffers, but it is included
@@ -601,13 +620,6 @@ public override void Write(byte[] buffer, int offset, int count)
                 throw new IOException("Maximum capacity exceeded");
             }
 
-            long requiredBuffers = (end + blockSize - 1) / blockSize;
-
-            if (requiredBuffers * blockSize > MaxStreamLength)
-            {
-                throw new IOException("Maximum capacity exceeded");
-            }
-
             this.EnsureCapacity((int)end);
 
             if (this.largeBuffer == null)
@@ -659,13 +671,6 @@ public override void Write(ReadOnlySpan<byte> source)
                 throw new IOException("Maximum capacity exceeded");
             }
 
-            long requiredBuffers = (end + blockSize - 1) / blockSize;
-
-            if (requiredBuffers * blockSize > MaxStreamLength)
-            {
-                throw new IOException("Maximum capacity exceeded");
-            }
-
             this.EnsureCapacity((int)end);
 
             if (this.largeBuffer == null)
@@ -850,9 +855,9 @@ public override void WriteTo(Stream stream)
                 stream.Write(this.largeBuffer, 0, this.length);
             }
         }
-        #endregion
+#endregion
 
-        #region Helper Methods
+#region Helper Methods
         private bool Disposed => Interlocked.Read(ref this.disposedState) != 0;
 
         private void CheckDisposed()
@@ -1005,6 +1010,6 @@ private void ReleaseLargeBuffer()
 
             this.largeBuffer = null;
         }
-        #endregion
+#endregion
     }
 }