cs456/a3/packets.py

import struct
        
# Init Packets
class ipacket:
    # creates an ipacket with routerid
    def __init__(this, rid):
        this.rid = rid
        
    # packs the packet into a packet (bytes)
    def package(this):
        return struct.pack("<I", this.rid)


# Hello Packets
class hpacket:
    # creates an hpacket with routerid and linkid
    def __init__(this, rid, lid):
        this.rid = rid
        this.lid = lid
    
    # packs the packet into a packet (bytes)
    def package(this):
        return struct.pack("<II", this.rid, this.lid)
        
        
# LSPDU Packets
class lpacket:
    # creates an lpacket with senderid, routerid, linkid, link cost, and sender link id
    def __init__(this, sid, rid, lid, cost, slid):
        this.sid = sid
        this.rid = rid
        this.lid = lid
        this.cost = cost
        this.slid = slid
        
    # packs the packet into a packet (bytes)
    def package(this):
        return struct.pack("<IIIII", this.sid, this.rid, this.lid, this.cost, this.slid)
        
        
# Link Class/struct
class link:
    # creates a link with id lid, cost cost
    def __init__(this, lid, cost):
        this.lid = lid
        this.cost = cost
        
    # packs the link into bytes
    def package(this):
        return struct.pack("<II", this.lid, this.cost)
        
    # returns link id
    def getlid(this):
        return this.lid
        
    # returns link cost
    def getcost(this):
        return this.cost
        

# CircuitDB Packets
class cpacket:
    # creates a cpacket with # of links nlinks, list of links links
    def __init__(this, nlinks, links):
        this.nklinks = nlinks
        this.links = links
        
    # packs the packet into a packet (bytes)
    def package(this):
        bytes = struct.pack("<I", this.nlinks)
        for i in this.links:
            bytes += i.package()
            
        return bytes
        
    # returns the number of links
    def getnlinks(this):
        return this.nlinks
        
    # returns the list of links
    def getlink(this):
        return this.links

# unpacks a packet and returns a packet of the corresponding type
def unpacket(bytes):
    size = len(bytes)
    
    # init packet
    if (size == 4):
        stuff = struct.unpack("<I", bytes)
        return (0, ipacket(stuff[0]))
    # hello packet
    elif (size == 8):
        stuff = struct.unpack("<II", bytes)
        return (1, hpacket(stuff[0], stuff[1]))
    # LSPDU Packet
    elif (size == 20):
        stuff = struct.unpack("<IIIII", bytes)
        return (2, lpacket(stuff[0], stuff[1], stuff[2], stuff[3], stuff[4]))
    # circuitDB packet
    else:
        nlinks = struct.unpack("<I", bytes)
        links = []
        for i in range(0, nlinks):
            stuff = struct.unpack("<II", bytes, i * 8 + 4)
            links.append(link(stuff[0], stuff[1]))
            
        return (3, cpacket(nlinks, links))