// Public Constructors
public Asn1Tag(Stream dataStream) : base()
{
Byte b = ReadByte(dataStream);
tagNumber = GetNumber(b);
tagType = GetType(b);
tagClass = GetClass(b);
if (tagNumber == Asn1TagNumber.HIGHNUMBER)
{
UInt32 tagNo = 0;
b = ReadByte(dataStream);
if ((b & 0x7F) == 0x00)
{
throw new IOException("Invalid tag number!");
}
else
{
while ((b & 0x80) == 0x80)
{
// Get bits from intermdeiate octets
tagNo |= (UInt32)(b & 0x7F);
tagNo <<= 7;
// Read next byte from dataStream
b = ReadByte(dataStream);
}
// Get bits from last octet
tagNo |= (UInt32)(b & 0x7F);
}
tagNumber = (Asn1TagNumber)tagNo;
}
}
/// <summary>
/// Decodes a tag from the buffer.
/// </summary>
/// <param name="buffer"></param>
/// <param name="tag"></param>
/// <returns>The number of the bytes consumed in the buffer to decode the tag.</returns>
public static int TagBerDecode(IAsn1DecodingBuffer buffer, out Asn1Tag tag)
{
byte prefix = buffer.ReadByte();
int firstTwoBits = (prefix >> 6);
Asn1TagType tagType = Asn1TagType.Private;
long tagValue;
switch (firstTwoBits)
{
case 0:
{
tagType = Asn1TagType.Universal;
} break;
case 1:
{
tagType = Asn1TagType.Application;
} break;
case 2:
{
tagType = Asn1TagType.Context;
} break;
case 3:
{
throw new NotImplementedException(ExceptionMessages.Unreachable);
};
}
tagValue = prefix & ((byte)(1 << 5) - 1);
if (tagValue <= 30)
{
tag = new Asn1Tag(tagType, tagValue);
if ((prefix & (1 << 5)) != 0)
{
tag.EncodingWay = EncodingWay.Constructed;
}
else
{
tag.EncodingWay = EncodingWay.Primitive;
}
return(1);
}
else
{
throw new NotImplementedException("Case tag > 30 is not implemented. Check X.690: 8.1.2.4.3.");
}
}
/// <summary>
/// Initializes a new instance of the Asn1Tag class with a given tag.
/// </summary>
/// <param name="TagValue">The value of the given tag.</param>
/// <param name="TagType">The type of the given tag.</param>
public Asn1Tag(Asn1TagType TagType, long TagValue)
{
this.type = TagType;
this.val = TagValue;
this.encodingWay = null;
}
/// <summary>
/// Initializes a new instance of the Asn1Tag class with a given tag.
/// </summary>
/// <param name="TagValue">The value of the given tag.</param>
/// <param name="TagType">The type of the given tag.</param>
public Asn1Tag(Asn1TagType TagType, long TagValue)
{
this.type = TagType;
this.val = TagValue;
this.encodingWay = null;
}
public Asn1Tag()
{
this.type = 0;
this.val = 0;
this.encodingWay = 0;
}
// Public Constructors
public Asn1Tag( Stream dataStream )
: base()
{
Byte b = ReadByte(dataStream);
tagNumber = GetNumber(b);
tagType = GetType(b);
tagClass = GetClass(b);
if (tagNumber == Asn1TagNumber.HIGHNUMBER)
{
UInt32 tagNo = 0;
b = ReadByte(dataStream);
if ((b & 0x7F) == 0x00)
throw new IOException("Invalid tag number!");
else
{
while ((b & 0x80) == 0x80)
{
// Get bits from intermdeiate octets
tagNo |= (UInt32)(b & 0x7F);
tagNo <<= 7;
// Read next byte from dataStream
b = ReadByte(dataStream);
}
// Get bits from last octet
tagNo |= (UInt32) (b & 0x7F);
}
tagNumber = (Asn1TagNumber) tagNo;
}
}
