Helpers.cs

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using System;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.Versioning;
using System.Security.Cryptography;
 
namespace Internal.Cryptography;
 
internal static class Helpers
{
    [UnsupportedOSPlatformGuard("android")]
    public static bool IsRC2Supported => !OperatingSystem.IsAndroid();
 
    public static bool UsesIv(this CipherMode cipherMode)
    {
        return cipherMode != CipherMode.ECB;
    }
 
    public static byte[] GetCipherIv(this CipherMode cipherMode, byte[] iv)
    {
        if (cipherMode.UsesIv())
        {
            if (iv == null)
            {
                throw new CryptographicException(System.SR.Cryptography_MissingIV);
            }
            return iv;
        }
        return null;
    }
 
    public static byte[] FixupKeyParity(this byte[] key)
    {
        byte[] array = new byte[key.Length];
        for (int i = 0; i < key.Length; i++)
        {
            array[i] = (byte)(key[i] & 0xFEu);
            byte b = (byte)((array[i] & 0xFu) ^ (uint)(array[i] >> 4));
            byte b2 = (byte)((b & 3u) ^ (uint)(b >> 2));
            if ((byte)((b2 & 1) ^ (b2 >> 1)) == 0)
            {
                array[i] |= 1;
            }
        }
        return array;
    }
 
    [return: NotNullIfNotNull("src")]
    public static byte[] CloneByteArray(this byte[] src)
    {
        if (src == null)
        {
            return null;
        }
        return (byte[])src.Clone();
    }
 
    public static int GetPaddingSize(this SymmetricAlgorithm algorithm, CipherMode mode, int feedbackSizeInBits)
    {
        return ((mode == CipherMode.CFB) ? feedbackSizeInBits : algorithm.BlockSize) / 8;
    }
 
    internal static bool TryCopyToDestination(this ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten)
    {
        if (source.TryCopyTo(destination))
        {
            bytesWritten = source.Length;
            return true;
        }
        bytesWritten = 0;
        return false;
    }
}