Simplify IP segments by removing redundant segments and merging adjacent segments.

gistfile1.py

# coding: UTF-8

import socket
import struct

def aton(addr):
    return struct.unpack('!l', socket.inet_aton(addr))

def ntoa(addr):
    return socket.inet_ntoa(struct.pack('!l', addr))

def mask_bits(mask):
    return ((1 << mask) - 1) << (32 - mask)

def simplify(ips):
    addrs = []

    # parse ip segments
    for ip in ips:
        if ip.find('/') == -1:
            addr, mask = ip, '32'
        else:
            addr, mask = ip.split('/')
        addr, = struct.unpack('!l', socket.inet_aton(addr))
        mask = int(mask)
        addr &= mask_bits(mask)
        addrs.append((addr, mask))

    if len(addrs) == 0:
        return []

    # remove redundant segments
    addrs.sort()
    result = [addrs[0]]
    for addr, mask in addrs[1:]:
        pre_addr, pre_mask = result[-1]
        if addr & mask_bits(pre_mask) != pre_addr:
            result.append((addr, mask))
    addrs = result

    # merge adjacent segments
    changed = True
    while changed:
        changed = False
        result = [addrs[0]]
        for addr, mask in addrs[1:]:
            pre_addr, pre_mask = result[-1]
            if mask != pre_mask or \
                    addr - pre_addr != 1 << (32 - mask):
                result.append((addr, mask))
            else:
                new_mask = mask - 1
                new_addr = addr & mask_bits(new_mask)
                result[-1] = (new_addr, new_mask)
                changed = True
        addrs = result

    # format ip segments again
    result = []
    for addr, mask in addrs:
        addr = ntoa(addr)
        if mask == 32:
            result.append(addr)
        else:
            result.append('%s/%d' % (addr, mask))

    return result

if __name__ == '__main__':
    import sys

    ips = []
    for line in sys.stdin:
        line = line.strip()
        if line:
            ips.append(line)
    print
    print '\n'.join(simplify(ips))