reduced extra allocations on array reverse operations

Author: Crypt32

Asn1Parser/Universal/Asn1Enumerated.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Linq;
 using System.Numerics;
 using SysadminsLV.Asn1Parser.Utils.CLRExtensions;
 
@@ -55,7 +54,9 @@ void m_decode(Asn1Reader asn) {
         var value = new BigInteger(payload, isUnsigned: true, isBigEndian: true);
 #else
         // Fallback for .NET Framework: reverse to little-endian
-        var value = new BigInteger(payload.ToArray().Cast<Byte>().Reverse().ToArray());
+        Byte[] bytes = payload.ToArray();
+        Array.Reverse(bytes);
+        var value = new BigInteger(bytes);
 #endif
         if (value > UInt64.MaxValue) {
             throw new InvalidDataException(String.Format(InvalidType, TYPE.ToString()));

Asn1Parser/Universal/Asn1Integer.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Linq;
 using System.Numerics;
 using SysadminsLV.Asn1Parser.Utils.CLRExtensions;
 
@@ -48,6 +47,15 @@ void m_encode(BigInteger inputInteger) {
         Initialize(Asn1Utils.EncodeAsReader(inputInteger.GetAsnBytes(), TYPE));
     }
     void m_decode(Asn1Reader asn) {
-        Value = new BigInteger(asn.GetPayload().Cast<Byte>().Reverse().ToArray());
+        ReadOnlySpan<Byte> payload = asn.GetPayloadAsMemory().Span;
+#if NET8_0_OR_GREATER
+        // BigInteger constructor with isBigEndian parameter (available in .NET 5+)
+        Value = new BigInteger(payload, isUnsigned: false, isBigEndian: true);
+#else
+        // Fallback for .NET Framework: reverse to little-endian
+        Byte[] bytes = payload.ToArray();
+        Array.Reverse(bytes);
+        Value = new BigInteger(bytes);
+#endif
     }
 }

Asn1Parser/Utils/CLRExtensions/BigIntegerExtensions.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Linq;
 using System.Numerics;
 
 namespace SysadminsLV.Asn1Parser.Utils.CLRExtensions;
@@ -14,6 +13,8 @@ internal static class BigIntegerExtensions {
     /// <param name="bigInteger">An <see cref="BigInteger"/> class instance.</param>
     /// <returns>Byte array in a big-endian order.</returns>
     public static ReadOnlySpan<Byte> GetAsnBytes(this BigInteger bigInteger) {
-        return bigInteger.ToByteArray().Cast<Byte>().Reverse().ToArray();
+        Byte[] bytes = bigInteger.ToByteArray();
+        Array.Reverse(bytes); // In-place reverse, single allocation
+        return bytes;
     }
 }