System.Text.EncodingPolyfills
namespace System.Text
{
internal static class EncodingPolyfills
{
public static int GetByteCount(this Encoding encoding, ReadOnlySpan<char> chars);
public static int GetCharCount(this Encoding encoding, ReadOnlySpan<byte> bytes);
public static int GetBytes(this Encoding encoding, string str, Span<byte> bytes);
public static int GetBytes(this Encoding encoding, ReadOnlySpan<char> chars, Span<byte> bytes);
public static int GetChars(this Encoding encoding, ReadOnlySpan<byte> bytes, Span<char> chars);
public static string GetString(this Encoding encoding, ReadOnlySpan<byte> bytes);
public static bool TryGetChars(this Encoding encoding, ReadOnlySpan<byte> bytes, Span<char> chars, out int charsWritten);
}
}