init commit

output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Utilities/IO/PushbackStream.cs

@@ -0,0 +1,45 @@
+using System;
+using System.IO;
+
+namespace Org.BouncyCastle.Utilities.IO;
+
+public class PushbackStream : FilterStream
+{
+	private int buf = -1;
+
+	public PushbackStream(Stream s)
+		: base(s)
+	{
+	}
+
+	public override int ReadByte()
+	{
+		if (buf != -1)
+		{
+			int result = buf;
+			buf = -1;
+			return result;
+		}
+		return base.ReadByte();
+	}
+
+	public override int Read(byte[] buffer, int offset, int count)
+	{
+		if (buf != -1 && count > 0)
+		{
+			buffer[offset] = (byte)buf;
+			buf = -1;
+			return 1;
+		}
+		return base.Read(buffer, offset, count);
+	}
+
+	public virtual void Unread(int b)
+	{
+		if (buf != -1)
+		{
+			throw new InvalidOperationException("Can only push back one byte");
+		}
+		buf = b & 0xFF;
+	}
+}