Refactoring of the asn1 module

The following changes are included:

- Decoding is a much simpler operation. The internal
  logic is based on stream of binary data, and not
  on string indexing anymore. Additionally,
  decoding used to look like this:

     bitmap = DerObject()
     bitmap.decode(input_buffer, True)
     if bitmap.isType('BIT STRING'):
        ... proceed with parsing ...
     else:
        ... error ...

  Whereas now, it is cleaner and more compact:

     bitmap = DerBitString()
     bitmap.decode(input_buffer)

  Any error condition will lead to an exception.

- isType() method has been removed because of the above.
- Added examples and documentation
- Added support IMPLICIT tags
- Added support for negative INTEGERs
- Added DerSetOf ASN.1 class
- DerObjectID can be initialized from the dotted representation of
  the Object ID.
- DerBitString has a new member 'value' to hold the binary
  string. The member 'payload' should not be accessed anymore.
- DerObjectID has a new member 'value' to hold the dotted representation
  of the Object ID string. The member 'payload' should not be accessed
  anymore.
- Added operator += to DER SEQUENCE. Now it is possible to do:

      my_str = DerOctetString(b'ZYZ')
      seq = DerSequence()
      seq += 0
      seq += my_str.encode()
- Update to test cases

0 files changed, 0 insertions, 0 deletions