Utility to convert an address to a hash and back.

addrhash.py

#!/usr/bin/env python
# Convert an address to a hash and back.
#
# Koen Bollen <meneer koenbollen nl>
# 2010 GPL
#

import socket
import struct
import base64

__all__ = [ "addr2hash", "hash2addr" ]

def addr2hash( addr ):
    """Convert an address pair to a hash."""

    host, port = addr

    try:
        host = socket.gethostbyname( host )
    except (socket.gaierror, socket.error):
        raise ValueError, "invalid host"

    try:
        port = int(port)
    except ValueError:
        raise ValueError, "invalid port"

    bytes  = socket.inet_aton( host )
    bytes += struct.pack( ">H", port )

    hash = base64.b64encode( bytes, "-_" )

    return hash

def hash2addr( hash ):
    """Convert a hash to an address pair."""

    try:
        if len(hash) != 8:
            raise TypeError
        bytes = base64.b64decode( hash, "-_" )
        if len(bytes) != 6:
            raise TypeError
    except TypeError:
        raise ValueError, "invalid hash"
    assert len(bytes) == 6

    host = socket.inet_ntoa( bytes[:4] )
    port, = struct.unpack( ">H", bytes[-2:] )

    return host, port

def main():
    """Sample and utility program."""

    import sys

    if len(sys.argv) >= 3:
        print addr2hash( (sys.argv[1], sys.argv[2]) )

    elif len(sys.argv) >= 2:
        try:
            host, port = hash2addr( sys.argv[1] )
            print host, port
        except ValueError:
            print >>sys.stderr, "error: invalid hash"

    else:
        print "Convert an address to a hash and back."
        print
        print "usage: %s host port" % sys.argv[0]
        print "   or: %s hash" % sys.argv[0]
        print
        print "Koen Bollen <meneer koenbollen nl>"
        print "2010 GPL"


if __name__ == "__main__":
    main()


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