From 79f3d7617fa1d4bc4b4b864330f184f93511c7f2 Mon Sep 17 00:00:00 2001
From: Sam Harwell <sam@tunnelvisionlabs.com>
Date: Tue, 4 Feb 2020 18:06:29 -0800
Subject: [PATCH] Implement SafeTensorflowHandle with extensions

---
 .../Util/SafeHandleExtensions.cs              | 54 +++++++++++++++++++
 .../Util/SafeHandleLease.cs                   | 36 +++++++++++++
 .../Util/SafeTensorflowHandle.cs              | 43 +++++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 src/TensorFlowNET.Core/Util/SafeHandleExtensions.cs
 create mode 100644 src/TensorFlowNET.Core/Util/SafeHandleLease.cs
 create mode 100644 src/TensorFlowNET.Core/Util/SafeTensorflowHandle.cs

diff --git a/src/TensorFlowNET.Core/Util/SafeHandleExtensions.cs b/src/TensorFlowNET.Core/Util/SafeHandleExtensions.cs
new file mode 100644
index 00000000..dca0bac3
--- /dev/null
+++ b/src/TensorFlowNET.Core/Util/SafeHandleExtensions.cs
@@ -0,0 +1,54 @@
+/*****************************************************************************
+   Copyright 2018 The TensorFlow.NET Authors. All Rights Reserved.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+******************************************************************************/
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Tensorflow.Util
+{
+    internal static class SafeHandleExtensions
+    {
+        /// <summary>
+        /// Acquires a lease on a safe handle. This method is intended to be used in the initializer of a <c>using</c>
+        /// statement.
+        /// </summary>
+        /// <param name="handle">The <see cref="SafeHandle"/> to lease.</param>
+        /// <returns>A <see cref="SafeHandleLease"/>, which must be disposed to release the resource.</returns>
+        /// <exception cref="ObjectDisposedException">If the lease could not be acquired.</exception>
+        public static SafeHandleLease Lease(this SafeHandle handle)
+        {
+            if (handle is null)
+                throw new ArgumentNullException(nameof(handle));
+
+            var success = false;
+            try
+            {
+                handle.DangerousAddRef(ref success);
+                if (!success)
+                    throw new ObjectDisposedException(handle.GetType().FullName);
+
+                return new SafeHandleLease(handle);
+            }
+            catch
+            {
+                if (success)
+                    handle.DangerousRelease();
+
+                throw;
+            }
+        }
+    }
+}
diff --git a/src/TensorFlowNET.Core/Util/SafeHandleLease.cs b/src/TensorFlowNET.Core/Util/SafeHandleLease.cs
new file mode 100644
index 00000000..dcc0e846
--- /dev/null
+++ b/src/TensorFlowNET.Core/Util/SafeHandleLease.cs
@@ -0,0 +1,36 @@
+/*****************************************************************************
+   Copyright 2018 The TensorFlow.NET Authors. All Rights Reserved.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+******************************************************************************/
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Tensorflow.Util
+{
+    /// <summary>
+    /// Represents a lease of a <see cref="SafeHandle"/>.
+    /// </summary>
+    /// <seealso cref="SafeHandleExtensions.Lease"/>
+    public readonly struct SafeHandleLease : IDisposable
+    {
+        private readonly SafeHandle _handle;
+
+        internal SafeHandleLease(SafeHandle handle)
+            => _handle = handle;
+
+        public void Dispose()
+            => _handle?.DangerousRelease();
+    }
+}
\ No newline at end of file
diff --git a/src/TensorFlowNET.Core/Util/SafeTensorflowHandle.cs b/src/TensorFlowNET.Core/Util/SafeTensorflowHandle.cs
new file mode 100644
index 00000000..abfb3446
--- /dev/null
+++ b/src/TensorFlowNET.Core/Util/SafeTensorflowHandle.cs
@@ -0,0 +1,43 @@
+/*****************************************************************************
+   Copyright 2018 The TensorFlow.NET Authors. All Rights Reserved.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+******************************************************************************/
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Tensorflow.Util
+{
+    public abstract class SafeTensorflowHandle : SafeHandle
+    {
+        private protected SafeTensorflowHandle()
+            : base(IntPtr.Zero, ownsHandle: true)
+        {
+        }
+
+        private protected SafeTensorflowHandle(IntPtr handle)
+            : base(IntPtr.Zero, ownsHandle: true)
+        {
+            SetHandle(handle);
+        }
+
+        private protected SafeTensorflowHandle(IntPtr handle, bool ownsHandle)
+            : base(IntPtr.Zero, ownsHandle)
+        {
+            SetHandle(handle);
+        }
+
+        public override bool IsInvalid => handle == IntPtr.Zero;
+    }
+}