Add C API for TF_StringInit.

src/TensorFlowNET.Core/Tensorflow.Binding.csproj

@@ -25,9 +25,11 @@ https://tensorflownet.readthedocs.io</Description>
 * Eager Mode is added finally.
 * tf.keras is partially working. 
 * tf.data is added.
-* autograph works partially.
+* Autograph works partially.
+* Improve memory usage.
 
-TensorFlow .NET v0.3x is focused on making more Keras API works</PackageReleaseNotes>
+TensorFlow .NET v0.3x is focused on making more Keras API works.
+Keras API is a separate package released as TensorFlow.Keras.</PackageReleaseNotes>
     <FileVersion>0.33.0.0</FileVersion>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
@@ -83,7 +85,7 @@ TensorFlow .NET v0.3x is focused on making more Keras API works</PackageReleaseN
     <PackageReference Include="MethodBoundaryAspect.Fody" Version="2.0.138" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="5.0.1" />
     <PackageReference Include="NumSharp.Lite" Version="0.1.12" />
-    <PackageReference Include="Protobuf.Text" Version="0.4.0" />
+    <PackageReference Include="Protobuf.Text" Version="0.5.0" />
     <PackageReference Include="Serilog.Sinks.Console" Version="3.1.1" />
   </ItemGroup>
 </Project>

src/TensorFlowNET.Core/Tensors/TF_TString_Type.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Tensorflow
+{
+    public enum TF_TString_Type
+    {
+        TF_TSTR_SMALL = 0,
+        TF_TSTR_LARGE = 1,
+        TF_TSTR_OFFSET = 2,
+        TF_TSTR_VIEW = 3
+    }
+}

src/TensorFlowNET.Core/Tensors/TStringHandle.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Tensorflow.Util;
+
+namespace Tensorflow
+{
+    public class TStringHandle : SafeTensorflowHandle
+    {
+        protected override bool ReleaseHandle()
+        {
+            c_api.TF_StringDealloc(handle);
+            return true;
+        }
+    }
+}

src/TensorFlowNET.Core/Tensors/Tensor.String.cs

@@ -8,7 +8,29 @@ namespace Tensorflow
 {
     public partial class Tensor
     {
-        public unsafe IntPtr StringTensor(string[] strings, TensorShape shape)
+        const ulong TF_TSRING_SIZE = 24;
+
+        public IntPtr StringTensor25(string[] strings, TensorShape shape)
+        {
+            var handle = c_api.TF_AllocateTensor(TF_DataType.TF_STRING,
+                shape.dims.Select(x => (long)x).ToArray(),
+                shape.ndim,
+                (ulong)shape.size * TF_TSRING_SIZE);
+
+            var data = c_api.TF_TensorData(handle);
+            var tstr = c_api.TF_StringInit(handle);
+            // AllocationHandle = tstr;
+            // AllocationType = AllocationType.Tensorflow;
+            for (int i = 0; i< strings.Length; i++)
+            {
+                c_api.TF_StringCopy(tstr, strings[i], strings[i].Length);
+                tstr += (int)TF_TSRING_SIZE;
+            }
+            // c_api.TF_StringDealloc(tstr);
+            return handle;
+        }
+
+        public IntPtr StringTensor(string[] strings, TensorShape shape)
         {
             // convert string array to byte[][]
             var buffer = new byte[strings.Length][];
@@ -61,11 +83,27 @@ namespace Tensorflow
             return handle;
         }
 
+        public string[] StringData25()
+        {
+            string[] strings = new string[c_api.TF_Dim(_handle, 0)];
+            var tstrings = TensorDataPointer; 
+            for (int i = 0; i< strings.Length; i++)
+            {
+                var tstringData = c_api.TF_StringGetDataPointer(tstrings);
+                /*var size = c_api.TF_StringGetSize(tstrings);
+                var capacity = c_api.TF_StringGetCapacity(tstrings);
+                var type = c_api.TF_StringGetType(tstrings);*/
+                strings[i] = c_api.StringPiece(tstringData);
+                tstrings += (int)TF_TSRING_SIZE;
+            }
+            return strings;
+        }
+
         /// <summary>
         ///     Extracts string array from current Tensor.
         /// </summary>
         /// <exception cref="InvalidOperationException">When <see cref="dtype"/> != TF_DataType.TF_STRING</exception>
-        public unsafe string[] StringData()
+        public string[] StringData()
         {
             var buffer = StringBytes();
 

src/TensorFlowNET.Core/Tensors/c_api.tensor.cs

@@ -181,6 +181,30 @@ namespace Tensorflow
         [DllImport(TensorFlowLibName)]
         public static extern unsafe ulong TF_StringEncode(byte* src, ulong src_len, byte* dst, ulong dst_len, SafeStatusHandle status);
 
+        [DllImport(TensorFlowLibName)]
+        public static extern IntPtr TF_StringInit(IntPtr t);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern void TF_StringCopy(IntPtr dst, string text, long size);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern void TF_StringAssignView(IntPtr dst, IntPtr text, long size);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern IntPtr TF_StringGetDataPointer(IntPtr tst);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern TF_TString_Type TF_StringGetType(IntPtr tst);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern ulong TF_StringGetSize(IntPtr tst);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern ulong TF_StringGetCapacity(IntPtr tst);
+
+        [DllImport(TensorFlowLibName)]
+        public static extern void TF_StringDealloc(IntPtr tst);
+
         /// <summary>
         /// Decode a string encoded using TF_StringEncode.
         /// </summary>

test/TensorFlowNET.Native.UnitTest/Tensors/TensorTest.cs

@@ -107,6 +107,32 @@ namespace Tensorflow.Native.UnitTest.Tensors
             Assert.IsTrue(Enumerable.SequenceEqual(nd.Data<float>(), new float[] { 1, 2, 3, 4, 5, 6 }));
         }
 
+        /// <summary>
+        /// Port from c_api_test.cc
+        /// `TEST_F(CApiAttributesTest, StringTensor)`
+        /// </summary>
+        [TestMethod, Ignore("Waiting for PR https://github.com/tensorflow/tensorflow/pull/46804")]
+        public void StringTensor()
+        {
+            string text = "Hello world!.";
+
+            var tensor = c_api.TF_AllocateTensor(TF_DataType.TF_STRING,
+                null,
+                0,
+                1 * 24);
+            var tstr = c_api.TF_StringInit(tensor);
+            var data = c_api.TF_StringGetDataPointer(tstr);
+            c_api.TF_StringCopy(tstr, text, text.Length);
+
+            Assert.AreEqual((ulong)text.Length, c_api.TF_StringGetSize(tstr));
+            Assert.AreEqual(text, c_api.StringPiece(data));
+            Assert.AreEqual((ulong)text.Length, c_api.TF_TensorByteSize(tensor));
+            Assert.AreEqual(0, c_api.TF_NumDims(tensor));
+
+            TF_DeleteTensor(tensor);
+            c_api.TF_StringDealloc(tstr);
+        }
+
         /// <summary>
         /// Port from tensorflow\c\c_api_test.cc
         /// `TEST(CAPI, SetShape)`