Helpers.cs

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using System;
using System.Diagnostics.CodeAnalysis;
using System.Security.Cryptography;
 
namespace Internal.Cryptography;
 
internal static class Helpers
{
    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[] TrimLargeIV(byte[] currentIV, int blockSizeInBits)
    {
        int num = checked(blockSizeInBits + 7) / 8;
        if (currentIV != null && currentIV.Length > num)
        {
            byte[] array = new byte[num];
            Buffer.BlockCopy(currentIV, 0, array, 0, array.Length);
            return array;
        }
        return currentIV;
    }
 
    [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;
    }
}