def decode_oid(self, packet):
"""
decode_oid(stream) -> object id
Decode octet stream into ASN.1 Object ID (returned as a list of
integer subIDs).
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'OBJID':
raise error.TypeMismatch('Non-Object ID type: '\
+ str(ord(packet[0])))
# Create a list for objid
oid = []
# Unpack the length
(length, size) = self.decode_length(packet[1:])
# Set up index
index = size + 1
# Get the first subid
subid = ord(packet[index])
oid.append(int(subid / 40))
oid.append(int(subid % 40))
# Progress index
index = index + 1
# Loop through the rest
while index < length + size + 1:
# Get a subid
subid = ord(packet[index])
if subid < 128:
oid.append(subid)
index = index + 1
else:
# Construct subid from a number of octets
next = subid
subid = 0
while next >= 128:
# Collect subid
subid = (subid << 7) + (next & 0x7F)
# Take next octet
index = index + 1
next = ord(packet[index])
# Just for sure
if index > length + size:
return bad_integer
# Append a subid to oid list
subid = (subid << 7) + next
oid.append(subid)
index = index + 1
# Return objid
return oid
def decode_uptime(self, packet):
"""
decode_uptime(stream) -> integer
Decode octet stream into ASN.1 uptime (integer value).
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'UPTIME':
raise error.TypeMismatch('Non-uptime type: ' + str(ord(packet[0])))
# Decode as unsigned integer
return self.decode_unsigned(packet)
def decode_timeticks(self, packet):
"""
decode_timeticks(stream) -> timeticks
Decode octet stream into ASN.1 timeticks data item (returned as
integer).
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'TIMETICKS':
raise error.TypeMismatch('Non-timeticks type: '\
+ str(ord(packet[0])))
# Decode as unsigned integer
return self.decode_unsigned(packet)
def decode_null(self, packet):
"""
decode_null(stream) -> None
Decode octet stream into ASN.1 NULL value.
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'NULL':
raise error.TypeMismatch('Non-NULL type: ' + str(ord(packet[0])))
# Now unpack the length
(length, size) = self.decode_length(packet[1:])
# Return nothing
return ''
def decode_string(self, packet):
"""
decode_string(stream) -> string
Decode octet stream into ASN.1 octet string.
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'OCTETSTRING':
raise error.TypeMismatch('Non-string type: ' + str(ord(packet[0])))
# Unpack the length
(length, size) = self.decode_length(packet[1:])
# Return the octets string
return packet[size + 1:size + length + 1]
def decode_opaque(self, packet):
"""
decode_opaque(stream) -> octets
Decode octet stream into ASN.1 opaque data item.
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'OPAQUE':
raise error.TypeMismatch('Non-opaque type: '\
+ str(ord(packet[0])))
# Now unpack the length
(length, size) = self.decode_length(packet[1:])
# Return the opaque string
return packet[size + 1:size + length + 1]
def decode_ipaddr(self, packet):
"""
decode_ipaddr(stream) -> ip address
Decode octet stream into ASN.1 IP address data item (returned
as string in dotted numeric notation).
"""
# Make sure data types matched
if self.decode_tag(ord(packet[0])) != 'IPADDRESS':
raise error.TypeMismatch('Non-IP address type: ' +
str(ord(packet[0])))
# Get the value from the packet
ipaddr = self.decode_sequence(packet)
# Check it is valid
if len(ipaddr) != 4:
raise error.BadIPAddress('Malformed IP address: ' + str(ipaddr))
# Return in dotted notation
return '%d.%d.%d.%d' % \
(ord(ipaddr[0]), ord(ipaddr[1]), \
ord(ipaddr[2]), ord(ipaddr[3]))