Fix the stucking of training when loading model.

src/TensorFlowNET.Core/Checkpoint/CheckpointReader.cs

@@ -1,29 +1,42 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Runtime.InteropServices;
-using System.Text;
-using Tensorflow.Util;
+using Tensorflow.Util;
 
 namespace Tensorflow.Checkpoint
 {
-    public class CheckpointReader : SafeTensorflowHandle
+    sealed class SafeCheckpointReaderHandle : SafeTensorflowHandle
     {
+        public SafeCheckpointReaderHandle(): base()
+        {
+            
+        }
+        public SafeCheckpointReaderHandle(IntPtr handle): base(handle)
+        {
+
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            c_api.TF_DeleteCheckpointReader(handle);
+            SetHandle(IntPtr.Zero);
+            return true;
+        }
+    }
+    public class CheckpointReader
+    {
+        private SafeCheckpointReaderHandle _handle;
         public Dictionary<string, TF_DataType> VariableToDataTypeMap { get; set; }
         public Dictionary<string, Shape> VariableToShapeMap { get; set; }
 
         public CheckpointReader(string filename)
         {
             Status status = new Status();
-            handle = c_api.TF_NewCheckpointReader(filename, status.Handle);
+            _handle = c_api.TF_NewCheckpointReader(filename, status.Handle);
             status.Check(true);
             ReadAllShapeAndType();
         }
 
         public int HasTensor(string name)
         {
-            return c_api.TF_CheckpointReaderHasTensor(handle, name);
+            return c_api.TF_CheckpointReaderHasTensor(_handle, name);
         }
 
         /// <summary>
@@ -33,45 +46,39 @@ namespace Tensorflow.Checkpoint
         /// <returns></returns>
         public string GetVariable(int index)
         {
-            return c_api.TF_CheckpointReaderGetVariable(handle, index);
+            return c_api.StringPiece(c_api.TF_CheckpointReaderGetVariable(_handle, index));
         }
 
         public int Size()
         {
-            return c_api.TF_CheckpointReaderSize(handle);
+            return c_api.TF_CheckpointReaderSize(_handle);
         }
 
         public TF_DataType GetVariableDataType(string name)
         {
-            return c_api.TF_CheckpointReaderGetVariableDataType(handle, name);
+            return c_api.TF_CheckpointReaderGetVariableDataType(_handle, name);
         }
 
         public Shape GetVariableShape(string name)
         {
-            // TODO(Rinne): Change it to a constant.
             int num_dims = GetVariableNumDims(name);
             long[] dims = new long[num_dims];
             Status status = new Status();
-            c_api.TF_CheckpointReaderGetVariableShape(handle, name, dims, num_dims, status.Handle);
+            c_api.TF_CheckpointReaderGetVariableShape(_handle, name, dims, num_dims, status.Handle);
             status.Check(true);
             return new Shape(dims);
         }
 
         public int GetVariableNumDims(string name)
         {
-            return c_api.TF_CheckpointReaderGetVariableNumDims(handle, name);
+            return c_api.TF_CheckpointReaderGetVariableNumDims(_handle, name);
         }
 
         public unsafe Tensor GetTensor(string name, TF_DataType dtype = TF_DataType.DtInvalid)
         {
             Status status = new Status();
-            var tensor = c_api.TF_CheckpointReaderGetTensor(handle, name, status.Handle);
+            var tensor = c_api.TF_CheckpointReaderGetTensor(_handle, name, status.Handle);
             status.Check(true);
-            var shape = GetVariableShape(name);
-            if(dtype == TF_DataType.DtInvalid)
-            {
-                dtype = GetVariableDataType(name);
-            }
             return new Tensor(tensor);
         }
 
@@ -89,16 +96,5 @@ namespace Tensorflow.Checkpoint
                 VariableToShapeMap[name] = shape;
             }
         }
-
-        protected override bool ReleaseHandle()
-        {
-            c_api.TF_DeleteCheckpointReader(handle);
-            return true;
-        }
-
-        public void Dispose()
-        {
-            c_api.TF_DeleteCheckpointReader(handle);
-        }
     }
 }

src/TensorFlowNET.Core/Checkpoint/c_api.checkpoint.cs

@@ -1,29 +1,27 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-using System.Runtime.InteropServices;
+using System.Runtime.InteropServices;
+using Tensorflow.Checkpoint;
 
 namespace Tensorflow
 {
     public unsafe partial class c_api
     {
         [DllImport(TensorFlowLibName)]
-        internal static extern IntPtr TF_NewCheckpointReader(string filename, SafeStatusHandle status);
+        internal static extern SafeCheckpointReaderHandle TF_NewCheckpointReader(string filename, SafeStatusHandle status);
         [DllImport(TensorFlowLibName)]
         internal static extern void TF_DeleteCheckpointReader(IntPtr reader);
         [DllImport(TensorFlowLibName)]
-        internal static extern int TF_CheckpointReaderHasTensor(IntPtr reader, string name);
+        internal static extern int TF_CheckpointReaderHasTensor(SafeCheckpointReaderHandle reader, string name);
         [DllImport(TensorFlowLibName)]
-        internal static extern string TF_CheckpointReaderGetVariable(IntPtr reader, int index);
+        internal static extern IntPtr TF_CheckpointReaderGetVariable(SafeCheckpointReaderHandle reader, int index);
         [DllImport(TensorFlowLibName)]
-        internal static extern int TF_CheckpointReaderSize(IntPtr reader);
+        internal static extern int TF_CheckpointReaderSize(SafeCheckpointReaderHandle reader);
         [DllImport(TensorFlowLibName)]
-        internal static extern TF_DataType TF_CheckpointReaderGetVariableDataType(IntPtr reader, string name);
+        internal static extern TF_DataType TF_CheckpointReaderGetVariableDataType(SafeCheckpointReaderHandle reader, string name);
         [DllImport(TensorFlowLibName)]
-        internal static extern void TF_CheckpointReaderGetVariableShape(IntPtr reader, string name, long[] dims, int num_dims, SafeStatusHandle status);
+        internal static extern void TF_CheckpointReaderGetVariableShape(SafeCheckpointReaderHandle reader, string name, long[] dims, int num_dims, SafeStatusHandle status);
         [DllImport(TensorFlowLibName)]
-        internal static extern int TF_CheckpointReaderGetVariableNumDims(IntPtr reader, string name);
+        internal static extern int TF_CheckpointReaderGetVariableNumDims(SafeCheckpointReaderHandle reader, string name);
         [DllImport(TensorFlowLibName)]
-        internal static extern SafeTensorHandle TF_CheckpointReaderGetTensor(IntPtr reader, string name, SafeStatusHandle status);
+        internal static extern SafeTensorHandle TF_CheckpointReaderGetTensor(SafeCheckpointReaderHandle reader, string name, SafeStatusHandle status);
     }
 }