IndefiniteLengthInputStream.cs :  » PDF » iTextSharp » Org » BouncyCastle » Asn1 » C# / CSharp Open Source

using System;
using System.IO;

namespace Org.BouncyCastle.Asn1{
  class IndefiniteLengthInputStream
    : LimitedInputStream
  {
    private int    _b1;
    private int    _b2;
    private bool  _eofReached = false;
    private bool  _eofOn00 = true;

    internal IndefiniteLengthInputStream(
      Stream inStream)
      : base(inStream)
    {
      _b1 = inStream.ReadByte();
      _b2 = inStream.ReadByte();

      if (_b2 < 0)
      {
        // Corrupted stream
        throw new EndOfStreamException();
      }

      CheckForEof();
    }

    internal void SetEofOn00(
      bool eofOn00)
    {
      _eofOn00 = eofOn00;
      CheckForEof();
    }

    private bool CheckForEof()
    {
      if (!_eofReached && _eofOn00 && (_b1 == 0x00 && _b2 == 0x00))
      {
        _eofReached = true;
        SetParentEofDetect(true);
      }

      return _eofReached;
    }

    public override int Read(
      byte[]  buffer,
      int    offset,
      int    count)
    {
      // Only use this optimisation if we aren't checking for 00
      if (_eofOn00 || count < 3)
        return base.Read(buffer, offset, count);

      if (_eofReached)
        return 0;

      int numRead = _in.Read(buffer, offset + 2, count - 2);

      if (numRead <= 0)
      {
        // Corrupted stream
        throw new EndOfStreamException();
      }

      buffer[offset] = (byte)_b1;
      buffer[offset + 1] = (byte)_b2;

      _b1 = _in.ReadByte();
      _b2 = _in.ReadByte();

      if (_b2 < 0)
      {
        // Corrupted stream
        throw new EndOfStreamException();
      }

      return numRead + 2;
    }

    public override int ReadByte()
    {
      if (CheckForEof())
        return -1;

      int b = _in.ReadByte();

      if (b < 0)
      {
        // Corrupted stream
        throw new EndOfStreamException();
      }

      int v = _b1;

      _b1 = _b2;
      _b2 = b;

      return v;
    }
  }
}