onnxruntime/csharp/src/Microsoft.ML.OnnxRuntime/NativeOnnxValueHelper.cs

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

using Microsoft.ML.OnnxRuntime.Tensors;
using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Microsoft.ML.OnnxRuntime
{
    internal class PinnedGCHandle : IDisposable
    {
        private GCHandle _handle;

        public PinnedGCHandle(GCHandle handle)
        {
            _handle = handle;
        }

        public IntPtr Pointer
        {
            get
            {
                return _handle.AddrOfPinnedObject();
            }
        }

        #region Disposable Support
        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                _handle.Free();
            }
        }
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        // No need for the finalizer
        // If this is not disposed timely GC can't help us
        #endregion
   }

    /// <summary>
    /// This helper class contains methods to create native OrtValue from a managed value object
    /// </summary>
    internal static class NativeOnnxValueHelper
    {
        /// <summary>
        /// Converts C# UTF-16 string to UTF-8 zero terminated
        /// byte[] instance
        /// </summary>
        /// <param name="s">string to be converted</param>
        /// <returns>UTF-8 encoded equivalent</returns>
        internal static byte[] StringToZeroTerminatedUtf8(string s)
        {
            byte[] utf8Bytes = UTF8Encoding.UTF8.GetBytes(s);
            Array.Resize(ref utf8Bytes, utf8Bytes.Length + 1);
            utf8Bytes[utf8Bytes.Length - 1] = 0;
            return utf8Bytes;
        }

        /// <summary>
        /// Reads UTF-8 encode string from a C zero terminated string
        /// and converts it into a C# UTF-16 encoded string
        /// </summary>
        /// <param name="nativeUtf8">pointer to native or pinned memory where Utf-8 resides</param>
        /// <returns></returns>
        internal static string StringFromNativeUtf8(IntPtr nativeUtf8)
        {
            // .NET 5.0 has Marshal.PtrToStringUTF8 that does the below
            int len = 0;
            while (Marshal.ReadByte(nativeUtf8, len) != 0) ++len;
            byte[] buffer = new byte[len];
            Marshal.Copy(nativeUtf8, buffer, 0, len);
            return Encoding.UTF8.GetString(buffer, 0, buffer.Length);
        }
    }

    internal static class TensorElementTypeConverter
    {
        public static void GetTypeAndWidth(TensorElementType elemType, out Type type, out int width)
        {
            TensorElementTypeInfo result = TensorBase.GetElementTypeInfo(elemType);
            if(result != null)
            {
                type = result.TensorType;
                width = result.TypeSize;
            }
            else
            {
                type = null;
                width = 0;
            }
        }
    }
}