public override int ReadByte()
{
var b = SourceStream.ReadByte();
if (b > -1)
{
outStream.WriteByte((byte)b);
}
return(b);
}
//public static int? ReadLength(byte[] data, int offset)
//{
// var lenByte = (int)data[offset];
// if (lenByte == -1)
// return null;
// if ((lenByte & 0x80) == 0)
// return lenByte;
// int length = 0;
// int lengthBytes = lenByte & 0x7F;
// if (lengthBytes == 0)
// return null;
// if (lengthBytes > 4)
// return null;
// for (int i = 0; i < lengthBytes; i++, offset++)
// {
// lenByte = (int)data[offset];
// if (lenByte == -1)
// throw new IOException("Unexpected end of stream");
// length <<= 8;
// length |= (int)lenByte;
// }
// return length;
//}
private int?ReadLength()
{
var lenByte = SourceStream.ReadByte();
if (lenByte == -1)
{
throw new IOException("Unexpected end of stream");
}
if ((lenByte & 0x80) == 0)
{
return(lenByte);
}
int length = 0;
int lengthBytes = lenByte & 0x7F;
if (lengthBytes == 0)
{
return(null);
}
if (lengthBytes > 4)
{
throw new IOException("Invalid length value");
}
for (int i = 0; i < lengthBytes; i++)
{
lenByte = SourceStream.ReadByte();
if (lenByte == -1)
{
throw new IOException("Unexpected end of stream");
}
length <<= 8;
length |= (int)lenByte;
}
return(length);
}
private uint?ReadNextTag()
{
uint tagValue = 0;
int byteCount = 0;
while (true)
{
if (byteCount >= 4)
{
throw new Exception(string.Format("Tag is more than 4 bytes long. Partial tag value: 0x{0:x8}", tagValue));
}
var thisByte = SourceStream.ReadByte();
if (thisByte == -1)
{
if (byteCount > 0)
{
throw new Exception(string.Format("Unexpected end of tag data. Partial tag value: 0x{0:x8}", tagValue));
}
return(null); // end of stream, no tag found
}
if (RemoveEMVPadding && byteCount == 0 && (thisByte == 0x00 || thisByte == 0xff)) // todo: check 0xff usage!!!
{
continue; // skip if not already reading tag (EMV allows 0x00 or 0xff padding between TLV entries)
}
byteCount++;
tagValue <<= 8;
tagValue |= (uint)thisByte;
if (byteCount == 1 && (thisByte & 0x1f) != 0x1f)
{
return(tagValue); // no more data (tag number is 0 to 30 inclusive, so only one octet used)
}
if (byteCount != 1 && (thisByte & 0x80) == 0)
{
return(tagValue); // no more data (bit 8 is not set for last octet)
}
}
}