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using System;
using System.IO;
namespace 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
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
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;
}
}
}
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