PushbackStream.cs :  » PDF » iTextSharp » Org » BouncyCastle » Utilities » IO » C# / CSharp Open Source

using System;
using System.IO;

using Org.BouncyCastle.Asn1.Utilities;

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 tmp = buf;
        buf = -1;
        return tmp;
      }

      return base.ReadByte();
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
      if (buf != -1 && count > 0)
      {
        // TODO Can this case be made more efficient?
        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;
    }
  }
}