private static void ParseTlv(byte[] rawTlv, ICollection <Tlv> result)
{
for (int i = 0, start = 0; i < rawTlv.Length; start = i)
{
// 0x00 and 0xFF can be used as padding before, between, and after tags
if (rawTlv[i] == 0x00)
{
i++;
continue;
}
// bit6 being 1 indicates that the tag is 'constructed' (contains more tags within it)
bool constructedTlv = (rawTlv[i] & 0x20) != 0;
// bit1 through 5 being 1 indicates that the tag is more than one byte long
// recognize this and keep looking until we find the last byte of the tag, indicated by bit8 being 0
bool multiByteTag = (rawTlv[i] & 0x1F) == 0x1F;
while (multiByteTag && (rawTlv[++i] & 0x80) != 0)
{
;
}
// i is on the last byte of the tag, so move it forward one and
// retreve the tag value from the raw tlv
i++;
int tag = GetInt(rawTlv, start, i - start);
// bit8 being 1 indicates that the length is multiple bytes long
bool multiByteLength = (rawTlv[i] & 0x80) != 0;
int length = multiByteLength ? GetInt(rawTlv, i + 1, rawTlv[i] & 0x1F) : rawTlv[i];
i = multiByteLength ? i + (rawTlv[i] & 0x1F) + 1 : i + 1;
// i is on the last byte of the length, so move it forward by the length we found
i += length;
// now that we know the start position and length of the data, retrieve it
// then create the Tlv object and add it to the list
byte[] rawData = new byte[i - start];
Array.Copy(rawTlv, start, rawData, 0, i - start);
var tlv = new Tlv(tag, length, rawData.Length - length, rawData);
result.Add(tlv);
// if this was a constructed tag, parse its value into individual Tlv children as well
if (constructedTlv)
{
ParseTlv(tlv.Value, tlv.Children);
}
}
}
private static void ParseTlv(byte[] rawTlv, ICollection<Tlv> result)
{
for(int i = 0, start = 0; i < rawTlv.Length; start = i)
{
// parse Tag
bool constructedTlv = (rawTlv[i] & 0x20) != 0;
bool moreBytes = (rawTlv[i] & 0x1F) == 0x1F;
while(moreBytes && (rawTlv[++i] & 0x80) != 0) ;
i++;
int tag = GetInt(rawTlv, start, i - start);
// parse Length
bool multiByteLength = (rawTlv[i] & 0x80) != 0;
int length = multiByteLength ? GetInt(rawTlv, i + 1, rawTlv[i] & 0x1F) : rawTlv[i];
i = multiByteLength ? i + (rawTlv[i] & 0x1F) + 1 : i + 1;
i += length;
byte[] rawData = new byte[i - start];
Array.Copy(rawTlv, start, rawData, 0, i - start);
var tlv = new Tlv(tag, length, rawData.Length - length, rawData);
result.Add(tlv);
if(constructedTlv)
{
ParseTlv(tlv.Value, tlv.Children);
}
}
}
