Add migrated to .NET 8.0 variant of Hcs.Client

Hcs.ClientNet/GostCryptography/Asn1/Gost/GostAsn1Choice.cs

@@ -0,0 +1,72 @@
+using GostCryptography.Asn1.Ber;
+using GostCryptography.Properties;
+
+namespace GostCryptography.Asn1.Gost
+{
+    public abstract class GostAsn1Choice : Asn1Choice
+    {
+        private const byte Null = 1;
+        private const byte Params = 2;
+
+        protected abstract short TagForm { get; }
+        protected abstract int TagIdCode { get; }
+        protected abstract Asn1Type CreateParams();
+
+        public override string ElemName
+        {
+            get
+            {
+                switch (ChoiceId)
+                {
+                    case Null:
+                        return "null_";
+                    case Params:
+                        return "params_";
+                }
+
+                return "UNDEFINED";
+            }
+        }
+
+        public override void Decode(Asn1BerDecodeBuffer buffer, bool explicitTagging, int implicitLength)
+        {
+            var tag = new Asn1Tag();
+            buffer.Mark();
+
+            var num = buffer.DecodeTagAndLength(tag);
+
+            if (tag.Equals(0, 0, NullTypeCode))
+            {
+                buffer.Reset();
+
+                SetElement(Null, new NullParams());
+                Element.Decode(buffer, true, num);
+            }
+            else
+            {
+                if (!tag.Equals(0, TagForm, TagIdCode))
+                {
+                    throw ExceptionUtility.CryptographicException(Resources.Asn1InvalidChoiceOptionTagException, tag, buffer.ByteCount);
+                }
+
+                buffer.Reset();
+
+                SetElement(Params, CreateParams());
+                Element.Decode(buffer, true, num);
+            }
+        }
+
+        public override int Encode(Asn1BerEncodeBuffer buffer, bool explicitTagging)
+        {
+            switch (ChoiceId)
+            {
+                case Null:
+                    return GetElement().Encode(buffer, true);
+                case Params:
+                    return GetElement().Encode(buffer, true);
+            }
+
+            throw ExceptionUtility.CryptographicException(Resources.Asn1InvalidChoiceOptionException);
+        }
+    }
+}