Implement SafeDeviceListHandle as a wrapper for TF_DeviceList

src/TensorFlowNET.Core/Device/SafeDeviceListHandle.cs

@@ -0,0 +1,40 @@
+/*****************************************************************************
+   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 Tensorflow.Util;
+
+namespace Tensorflow.Device
+{
+    public sealed class SafeDeviceListHandle : SafeTensorflowHandle
+    {
+        private SafeDeviceListHandle()
+        {
+        }
+
+        public SafeDeviceListHandle(IntPtr handle)
+            : base(handle)
+        {
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            c_api.TF_DeleteDeviceList(handle);
+            SetHandle(IntPtr.Zero);
+            return true;
+        }
+    }
+}

src/TensorFlowNET.Core/Device/c_api.device.cs

@@ -16,6 +16,7 @@
 
 using System;
 using System.Runtime.InteropServices;
+using Tensorflow.Device;
 using Tensorflow.Eager;
 
 namespace Tensorflow
@@ -36,7 +37,7 @@ namespace Tensorflow
         /// <param name="list">TF_DeviceList*</param>
         /// <returns></returns>
         [DllImport(TensorFlowLibName)]
-        public static extern int TF_DeviceListCount(IntPtr list);
+        public static extern int TF_DeviceListCount(SafeDeviceListHandle list);
 
         /// <summary>
         /// Retrieves the type of the device at the given index.
@@ -46,7 +47,7 @@ namespace Tensorflow
         /// <param name="status">TF_Status*</param>
         /// <returns></returns>
         [DllImport(TensorFlowLibName)]
-        public static extern IntPtr TF_DeviceListType(IntPtr list, int index, SafeStatusHandle status);
+        public static extern IntPtr TF_DeviceListType(SafeDeviceListHandle list, int index, SafeStatusHandle status);
 
         /// <summary>
         /// Deallocates the device list.
@@ -77,6 +78,6 @@ namespace Tensorflow
         /// <param name="index"></param>
         /// <param name="status">TF_Status*</param>
         [DllImport(TensorFlowLibName)]
-        public static extern IntPtr TF_DeviceListName(IntPtr list, int index, SafeStatusHandle status);
+        public static extern IntPtr TF_DeviceListName(SafeDeviceListHandle list, int index, SafeStatusHandle status);
     }
 }

src/TensorFlowNET.Core/Eager/c_api.eager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Runtime.InteropServices;
+using Tensorflow.Device;
 using Tensorflow.Eager;
 using TFE_Executor = System.IntPtr;
 
@@ -317,7 +318,7 @@ namespace Tensorflow
         /// <param name="status">TF_Status*</param>
         /// <returns></returns>
         [DllImport(TensorFlowLibName)]
-        public static extern IntPtr TFE_ContextListDevices(SafeContextHandle ctx, SafeStatusHandle status);
+        public static extern SafeDeviceListHandle TFE_ContextListDevices(SafeContextHandle ctx, SafeStatusHandle status);
 
         /// <summary>
         /// 

test/TensorFlowNET.UnitTest/NativeAPI/CApiTest.cs

@@ -1,6 +1,7 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using System;
 using Tensorflow;
+using Tensorflow.Device;
 using Tensorflow.Eager;
 using Buffer = System.Buffer;
 
@@ -8,14 +9,14 @@ namespace TensorFlowNET.UnitTest
 {
     public class CApiTest
     {
-        protected TF_Code TF_OK = TF_Code.TF_OK;
-        protected TF_DataType TF_FLOAT = TF_DataType.TF_FLOAT;
-        protected TF_DataType TF_BOOL = TF_DataType.TF_BOOL;
+        protected static readonly TF_Code TF_OK = TF_Code.TF_OK;
+        protected static readonly TF_DataType TF_FLOAT = TF_DataType.TF_FLOAT;
+        protected static readonly TF_DataType TF_BOOL = TF_DataType.TF_BOOL;
 
         protected void EXPECT_TRUE(bool expected, string msg = "")
             => Assert.IsTrue(expected, msg);
 
-        protected void EXPECT_EQ(object expected, object actual, string msg = "")
+        protected static void EXPECT_EQ(object expected, object actual, string msg = "")
             => Assert.AreEqual(expected, actual, msg);
 
         protected void CHECK_EQ(object expected, object actual, string msg = "")
@@ -63,10 +64,10 @@ namespace TensorFlowNET.UnitTest
         protected TF_Code TF_GetCode(Status s)
             => s.Code;
 
-        protected TF_Code TF_GetCode(SafeStatusHandle s)
+        protected static TF_Code TF_GetCode(SafeStatusHandle s)
             => c_api.TF_GetCode(s);
 
-        protected string TF_Message(SafeStatusHandle s)
+        protected static string TF_Message(SafeStatusHandle s)
             => c_api.StringPiece(c_api.TF_Message(s));
 
         protected SafeStatusHandle TF_NewStatus()
@@ -141,21 +142,18 @@ namespace TensorFlowNET.UnitTest
         protected string TFE_TensorHandleBackingDeviceName(IntPtr h, SafeStatusHandle status)
             => c_api.StringPiece(c_api.TFE_TensorHandleBackingDeviceName(h, status));
 
-        protected IntPtr TFE_ContextListDevices(SafeContextHandle ctx, SafeStatusHandle status)
+        protected SafeDeviceListHandle TFE_ContextListDevices(SafeContextHandle ctx, SafeStatusHandle status)
             => c_api.TFE_ContextListDevices(ctx, status);
 
-        protected int TF_DeviceListCount(IntPtr list)
+        protected int TF_DeviceListCount(SafeDeviceListHandle list)
             => c_api.TF_DeviceListCount(list);
 
-        protected string TF_DeviceListType(IntPtr list, int index, SafeStatusHandle status)
+        protected string TF_DeviceListType(SafeDeviceListHandle list, int index, SafeStatusHandle status)
             => c_api.StringPiece(c_api.TF_DeviceListType(list, index, status));
 
-        protected string TF_DeviceListName(IntPtr list, int index, SafeStatusHandle status)
+        protected string TF_DeviceListName(SafeDeviceListHandle list, int index, SafeStatusHandle status)
             => c_api.StringPiece(c_api.TF_DeviceListName(list, index, status));
 
-        protected void TF_DeleteDeviceList(IntPtr list)
-            => c_api.TF_DeleteDeviceList(list);
-
         protected IntPtr TFE_TensorHandleCopyToDevice(IntPtr h, SafeContextHandle ctx, string device_name, SafeStatusHandle status)
             => c_api.TFE_TensorHandleCopyToDevice(h, ctx, device_name, status);
 

test/TensorFlowNET.UnitTest/NativeAPI/Eager/CApi.Eager.Context.cs

@@ -1,6 +1,6 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
-using System;
 using Tensorflow;
+using Tensorflow.Device;
 using Tensorflow.Eager;
 
 namespace TensorFlowNET.UnitTest.NativeAPI
@@ -21,13 +21,15 @@ namespace TensorFlowNET.UnitTest.NativeAPI
                 return c_api.TFE_NewContext(opts, status);
             }
 
-            IntPtr devices;
-            using (var ctx = NewContext(status))
+            static SafeDeviceListHandle ListDevices(SafeStatusHandle status)
             {
-                devices = c_api.TFE_ContextListDevices(ctx, status);
+                using var ctx = NewContext(status);
+                var devices = c_api.TFE_ContextListDevices(ctx, status);
                 EXPECT_EQ(TF_OK, TF_GetCode(status), TF_Message(status));
+                return devices;
             }
 
+            using var devices = ListDevices(status);
             EXPECT_EQ(TF_OK, TF_GetCode(status), TF_Message(status));
 
             int num_devices = c_api.TF_DeviceListCount(devices);
@@ -37,8 +39,6 @@ namespace TensorFlowNET.UnitTest.NativeAPI
                 EXPECT_NE("", c_api.TF_DeviceListName(devices, i, status), TF_Message(status));
                 EXPECT_EQ(TF_OK, TF_GetCode(status), TF_Message(status));
             }
-
-            c_api.TF_DeleteDeviceList(devices);
         }
     }
 }

test/TensorFlowNET.UnitTest/NativeAPI/Eager/CApi.Eager.cs

@@ -43,8 +43,8 @@ namespace TensorFlowNET.UnitTest.NativeAPI
 
         bool GetDeviceName(SafeContextHandle ctx, ref string device_name, string device_type)
         {
-            var status = TF_NewStatus();
-            var devices = TFE_ContextListDevices(ctx, status);
+            using var status = TF_NewStatus();
+            using var devices = TFE_ContextListDevices(ctx, status);
             CHECK_EQ(TF_OK, TF_GetCode(status), TF_Message(status));
 
             int num_devices = TF_DeviceListCount(devices);
@@ -57,12 +57,10 @@ namespace TensorFlowNET.UnitTest.NativeAPI
                 if (dev_type == device_type)
                 {
                     device_name = dev_name;
-                    TF_DeleteDeviceList(devices);
                     return true;
                 }
             }
 
-            TF_DeleteDeviceList(devices);
             return false;
         }