src/csharp/Grpc.Core/Internal/MetadataArraySafeHandle.cs

#region Copyright notice and license
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// in the documentation and/or other materials provided with the
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#endregion
using System;
using System.Runtime.InteropServices;
using System.Threading.Tasks;

namespace Grpc.Core.Internal
{
    /// <summary>
    /// grpc_metadata_array from <grpc/grpc.h>
    /// </summary>
    internal class MetadataArraySafeHandle : SafeHandleZeroIsInvalid
    {
        [DllImport("grpc_csharp_ext.dll")]
        static extern MetadataArraySafeHandle grpcsharp_metadata_array_create(UIntPtr capacity);

        [DllImport("grpc_csharp_ext.dll", CharSet = CharSet.Ansi)]
        static extern void grpcsharp_metadata_array_add(MetadataArraySafeHandle array, string key, byte[] value, UIntPtr valueLength);

        [DllImport("grpc_csharp_ext.dll")]
        static extern UIntPtr grpcsharp_metadata_array_count(IntPtr metadataArray);

        [DllImport("grpc_csharp_ext.dll")]
        static extern IntPtr grpcsharp_metadata_array_get_key(IntPtr metadataArray, UIntPtr index);

        [DllImport("grpc_csharp_ext.dll")]
        static extern IntPtr grpcsharp_metadata_array_get_value(IntPtr metadataArray, UIntPtr index);

        [DllImport("grpc_csharp_ext.dll")]
        static extern UIntPtr grpcsharp_metadata_array_get_value_length(IntPtr metadataArray, UIntPtr index);

        [DllImport("grpc_csharp_ext.dll")]
        static extern void grpcsharp_metadata_array_destroy_full(IntPtr array);

        private MetadataArraySafeHandle()
        {
        }
            
        public static MetadataArraySafeHandle Create(Metadata metadata)
        {
            // TODO(jtattermusch): we might wanna check that the metadata is readonly 
            var metadataArray = grpcsharp_metadata_array_create(new UIntPtr((ulong)metadata.Count));
            for (int i = 0; i < metadata.Count; i++)
            {
                grpcsharp_metadata_array_add(metadataArray, metadata[i].Key, metadata[i].ValueBytes, new UIntPtr((ulong)metadata[i].ValueBytes.Length));
            }
            return metadataArray;
        }

        /// <summary>
        /// Reads metadata from pointer to grpc_metadata_array
        /// </summary>
        public static Metadata ReadMetadataFromPtrUnsafe(IntPtr metadataArray)
        {
            if (metadataArray == IntPtr.Zero)
            {
                return null;
            }

            ulong count = grpcsharp_metadata_array_count(metadataArray).ToUInt64();

            var metadata = new Metadata();
            for (ulong i = 0; i < count; i++)
            {
                var index = new UIntPtr(i);
                string key = Marshal.PtrToStringAnsi(grpcsharp_metadata_array_get_key(metadataArray, index));
                var bytes = new byte[grpcsharp_metadata_array_get_value_length(metadataArray, index).ToUInt64()];
                Marshal.Copy(grpcsharp_metadata_array_get_value(metadataArray, index), bytes, 0, bytes.Length);
                metadata.Add(new Metadata.Entry(key, bytes));
            }
            return metadata;
        }

        internal IntPtr Handle
        {
            get
            {
                return handle;
            }
        }

        protected override bool ReleaseHandle()
        {
            grpcsharp_metadata_array_destroy_full(handle);
            return true;
        }
    }
}