WaterFlush/Packages/com.tivadar.best.http/Runtime/3rdParty/BouncyCastle/util/io/PushbackStream.cs

#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
#pragma warning disable
using System;
using System.IO;

namespace Best.HTTP.SecureProtocol.Org.BouncyCastle.Utilities.IO
{
	public class PushbackStream
		: FilterStream
	{
		private int m_buf = -1;

		public PushbackStream(Stream s)
			: base(s)
		{
		}

#if NETCOREAPP2_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER || (UNITY_2021_2_OR_NEWER && (NET_STANDARD_2_0 || NET_STANDARD_2_1))
        public override void CopyTo(Stream destination, int bufferSize)
        {
			if (m_buf != -1)
			{
				destination.WriteByte((byte)m_buf);
                m_buf = -1;
            }

            s.CopyTo(destination, bufferSize);
        }
#endif

        public override int Read(byte[] buffer, int offset, int count)
		{
			Streams.ValidateBufferArguments(buffer, offset, count);

			if (m_buf != -1)
			{
				if (count < 1)
					return 0;

				buffer[offset] = (byte)m_buf;
				m_buf = -1;
				return 1;
			}

			return s.Read(buffer, offset, count);
		}

#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER || UNITY_2021_2_OR_NEWER
        public override int Read(Span<byte> buffer)
        {
			if (m_buf != -1)
			{
                if (buffer.IsEmpty)
                    return 0;

                buffer[0] = (byte)m_buf;
                m_buf = -1;
                return 1;
            }

            return s.Read(buffer);
        }
#endif

        public override int ReadByte()
		{
			if (m_buf != -1)
			{
				int tmp = m_buf;
				m_buf = -1;
				return tmp;
			}

			return base.ReadByte();
		}

		public virtual void Unread(int b)
		{
			if (m_buf != -1)
				throw new InvalidOperationException("Can only push back one byte");

			m_buf = b & 0xFF;
		}
	}
}
#pragma warning restore
#endif